Introduction to electricity

Transcription

1 Gill Sans Bold Science Stage 4 Introduction to electricity Sets 1 to K 6 A 9 V K 9 A V 10 K A 16 K A S 31718

2 Number: Title: Introduction to electricity This publication is copyright New South Wales Department of Education and Training (DET), however it may contain material from other sources which is not owned by DET. We would like to acknowledge the following people and organisations whose material has been used: Extract from Science Syllabus Years 7-10 Board of Studies, NSW 2003 Introduction pp vi-viii COMMONWEALTH OF AUSTRALIA Copyright Regulations 1969 WARNING This material has been reproduced and communicated to you on behalf of the New South Wales Department of Education and Training (Centre for Learning Innovation) pursuant to Part VB of the Copyright Act 1968 (the Act). The material in this communication may be subject to copyright under the Act. Any further reproduction or communication of this material by you may be the subject of copyright protection under the Act. CLI Project Team acknowledgement: Writer: Editors: Illustrator: Pam Wild Dick Alliband and Rhonda Caddy Barbara Gurney All reasonable efforts have been made to obtain copyright permissions. All claims will be settled in good faith. Published by Centre for Learning Innovation (CLI) 51 Wentworth Rd Strathfield NSW 2135 Copyright of this material is reserved to the Crown in the right of the State of New South Wales. Reproduction or transmittal in whole, or in part, other than in accordance with provisions of the Copyright Act, is prohibited without the written authority of the Centre for Learning Innovation (CLI). State of New South Wales, Department of Education and Training 2005.

3 Before you begin I What do you need to know before you begin this unit? You should already be able to: describe similarities and differences in a scientific way state that atoms are the smallest particles of matter that can exist on their own, and that everything is made from atoms add and subtract positive and negative numbers identify electrical, heat, light, sound, kinetic, potential and chemical as names used to describe energy identify forms of energy in different situations identify that energy may be passed from one place to another or change form, but does not disappear present information in a table. Here are some words that you should understand for this unit. Some of these words have more than one meaning. The meanings given are the ones needed within this unit. adjective a word to help describe an object or person; for example, black is an adjective to describe a cat (a black cat) appliance a piece of equipment, usually used in the home, and usually operated with electrical energy bright a way of describing a large amount of light chemical a substance; plastic, acid, metals and the gases that make up air are all examples of chemicals coding changing something you are familiar with into a code e.g. numbers changed to colour bands on a resistor concept map a diagram that shows words related to a topic and how they are linked. Links are shown with labelled lines or arrows decoding changing a code into a more familiar communication e.g. colour bands changed to resistance in ohms of a resistor deduce work out by thinking logically device piece of equipment dim a way of describing a small amount of light Introduction to electricity

4 II dynamic moving or changing parallel running side by side, rather than one after the other; like train tracks prediction a suggestion, based on evidence, about what may happen rim edge, usually of an object that is a rounded shape stab in the dark a guess; an answer or idea that you have no reason to think should be correct static still; not moving or changing ultramarathon a very, very long foot race vane part of a device that can turn or move on its own vigorous rapidly; using lots of movement Introduction to electricity

5 Symbols used in this unit III You will find these symbols used in this unit. The key below shows you the meaning of each symbol. This symbol appears beside exercises that should be sent to your teacher. This symbol marks a mastery test. This is a test that you do for yourself, to see if you are ready to complete a send-in exercise or begin something new. There is something for you to cut. Introduction to electricity

6 IV Unit outline Set 1 Set 2 Set 3 Finding out about electricity Lesson 1 What is electricity? Lessons 2 and 3 Investigating static electricity Lesson 4 Energy transformations Lesson 5 Getting ready for Set 2 Making an electrical circuit Lessons 6 to 8 Making a tester Lesson 9 Resistor coding and decoding Lesson 10 What is an electrical circuit? Investigating electrical circuits Lessons 11 and 12 Energy for a circuit Lesson 13 Diagrams for circuits Lesson 14 Predicting Lesson 15 Investigating Introduction to electricity

7 What will you learn in this unit? V In this unit, you will learn to describe and explain some concepts about electrical energy and identify some examples of where electricity is used, particularly in technological developments. You ll learn about: how objects become electrostatically charged and what charged objects do electrical circuits different kinds of batteries, how they are used and how you can reduce damage to the environment from used batteries circuit symbols and circuit diagrams. You ll learn to: make and test predictions make and test an electrical circuit make generalisations draw circuit diagrams. Assessment Throughout the lessons in Introduction to electricity, you will be able to see how well you can do these things by completing activities and answering questions, then checking your own answers. You will show your teacher what you have achieved by completing the exercises in the send-in pages. Indicative time This unit should take about 15 hours to complete. Introduction to electricity

8 VI Outcomes and essential content 4.2 A student uses examples to illustrate how models, theories and laws contribute to an understanding of phenomena. 4/5.2 Students learn about the nature and practice of science. Students learn to: e) use examples which show that scientists isolate a set of observations, identify trends and patterns and construct hypotheses or models to explain these. 4.3 A student identifies areas of everyday life that have been affected by scientific developments. 4/5.3 Students learn about the applications and uses of science. Students learn to: a) identify and describe examples of scientific concepts and principles that have been used in technological developments (including Australian examples). 4.6 A student identifies and describes energy changes and the action of forces in common situations Students learn about the law of conservation of energy. Students learn to: a) identify situations or phenomena in which different forms of energy are evident b) use models to describe different forms of energy c) identify objects that possess energy because of their motion (kinetic) or because of their properties (potential) Students learn about electrical energy. Students learn to: a) associate electricity with energy transfer in a simple circuit b) construct and draw circuits to show transfer of energy Students learn about electrostatic force. Students learn to: a) describe ways in which objects acquire an electrostatic charge b) identify everyday situations where the effects of electrostatic forces can be observed c) describe the behaviour of charges when they are brought close to each other. Introduction to electricity

9 VII 4.12 A student identifies, using examples, common simple devices and explains why they are used Students learn about technology. Students learn to: b) identify a variety of energy transformations in everyday devices involving electrical, sound, light and/or heat energy A student follows a sequence of instructions to undertake a first-hand investigation. 4/5.14 Students learn about performing first-hand investigations. Students learn to: a) follow the planned procedure when performing an investigation b) safely and effectively construct, assemble and manipulate identified equipment A student accesses information from identified secondary sources. 4/5.16 Students learn about gathering information from secondary sources. Students learn to: c) extract information from column graphs, histograms, divided bar and sector graphs, line graphs, composite graphs, flow diagrams, other texts and audio/visual resources d) summarise information from identified oral and written secondary sources A student evaluates the relevance of data and information. 4/5.17 Students learn about processing information. Students learn to: d) organise data using a variety of methods including diagrams, tables, spreadsheets and databases f) identify trends, patterns, relationships and contradictions in data and information A student with guidance, presents information to an audience to achieve a particular purpose. 4/5.18 Students learn about presenting information. Students learn to: e) use drawings, diagrams, graphs, tables, databases, spreadsheets and flow charts to show relationships and present information clearly and/or succinctly. Introduction to electricity

10 VIII 4.19 A student draws conclusions based on information available. 4/5.19 Students learn about thinking critically. Students learn to: d) make generalisations in relation to a relevant set of observations or experimental results e) anticipate and/or respond to problems as they arise in practical situations f) use models, including mathematical ones, to explain phenomena or make predictions g) use cause and effect relationships to explain ideas A student undertakes a variety of individual and team tasks with guidance. 4/5.22 Students learn about working individually. Students learn to: a) independently plan and conduct investigations, communicate information understanding and solve problems b) set and work to realistic timelines and goals. Extracts from Science Years 7-10 syllabus Board of Studies, NSW 2003, accessed 20 July Introduction to electricity

11 What do you need for this unit? IX The table below shows the materials that you need for this unit, and when you will use them. Notice that there is a list of things you have to supply yourself from around your home. This list may help you to plan ahead in case you have to shop for any of these materials. Set 1 Lesson 1 a plastic comb or a plastic ruler woollen material or a woollen jumper some scrap paper. Lessons 2 and 3 a balloon some woollen fabric (or a woollen jumper) 2 plastic combs, plastic rulers or plastic teaspoons a tiny piece of torn paper a clock glass. Lesson 5 Electronic kit, e.g. from Dick Smith or Jaycar stores, containing: battery board bag of springs and clips (or screws and washers) silver-coloured wire two plastic-coated wires with alligator clips screwdriver (if you have screws and washers) battery clip LED (light emitting diodes) protection diodes 390 ohm resistors (orange white brown gold bands). Introduction to electricity

12 X Set 2 Lessons 6 to 8 battery board 8 springs and clips (or screws and washers) silver-coloured wire 2 plastic-coated wires with alligator clips screwdriver (if you have screws and washers) battery clip 1 protection diode ohm resistor (orange, white, brown and gold bands) 1 LED. Set 3 Lessons 11 and 12 scissors sticky tape or glue Lesson 13 completed tester circuit from Set 2 scrap paper ruler sharp pencil Lesson 15 completed tester circuit from Set 2 ten materials from around your home Introduction to electricity

13 Science Stage 4 NEW SOUTH WALES DEPARTMENT OF EDUCATION AND TRAINING Introduction to electricity Set 1: Finding out about electricity 1 5 K 6 A 9 V K 9 A V 10 K A 16 K A 14 15

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15 Introduction to electricity i Set The hand points to the names of the lessons in this set. 1 Finding out about electricity Lesson 1 What is electricity? Lessons 2 and 3 Investigating static electricity Lesson 4 Energy transformations Lesson 5 Getting ready for Set 2 Set 2 Set 3 Making an electrical circuit Lessons 6 to 8 Making a tester Lesson 9 Resistor coding and decoding Lesson 10 What is an electrical circuit? Investigating electrical circuits Lessons 11 and 12 Energy for a circuit Lesson 13 Diagrams for circuits Lesson 14 Predicting Lesson 15 Investigating Introduction to electricity Set 1

16 ii Set 1: Finding out about electricity Contents What will you learn in Set 1?... iii What do you need for Set 1?... iv Lesson 1 What is electricity?... 1 Lessons 2 and 3 Investigating static electricity... 9 Lesson 4 Energy transformations Lesson 5 Getting ready for Set Suggested answers Send-in pages Introduction to electricity Set 1

17 What will you learn in Set 1? iii In Set 1, you will have opportunities to achieve and demonstrate the following statements. draw a concept map about electricity define static electricity define dynamic electricity electrostatically charge objects by rubbing them electrostatically charge objects by touching them with a charged object explain why objects become electrostatically charged match diagrams and headings with text about electrostatics demonstrate that electrostatically charged objects attract uncharged objects demonstrate that like charges repel recall that opposite charges attract write simple equations for transformations of energy Introduction to electricity Set 1

18 iv What do you need for Set 1? Here is a reminder of the items you need for Set 1. To save time, it might be a good idea to get all these things ready before you start. Lesson 1 a plastic comb or a plastic ruler woollen material or a woollen jumper some scrap paper, torn into pieces that are smaller than 1 cm in any direction. Lessons 2 and 3 a balloon some woollen fabric (or a woollen jumper) 2 stick-shaped objects made from the same kind of plastic; for example, two plastic combs, plastic rulers or plastic teaspoons running water from a tap a tiny piece of torn paper, smaller than 1 cm in any direction a clock glass or a flattened plastic bottle such as a shampoo bottle. Lesson 5 Electronic kit, e.g. from Dick Smith or Jaycar stores, containing: battery board bag of springs and clips (or screws and washers) silver-coloured wire two plastic-coated wires with alligator clips screwdriver (if you have screws and washers) battery clip one LED (light emitting diode) one protection diode one 390 ohm resistor (orange white brown gold bands). Introduction to electricity Set 1

19 1 Lesson 1 What is electricity? What do you think electricity is? In the space below, make a concept map by writing as many words as you can think of that are related to electricity. Then draw lines to link the ideas to electricity or each other, if you can. Label each line with the reason that you think the words are linked. electricity Introduction to electricity Set 1

20 2 Everyone knows something about electricity so I m sure that you came up with some good ideas about what electricity is. But do you think your ideas about electricity are very scientific? You ll be able to judge by the end of this lesson. Here is an example of electricity that you may not have thought about. For this activity, you will need: a plastic comb or a plastic ruler woollen material or a woollen jumper some scrap paper, torn into pieces that are smaller than 1 cm in any direction. What to do: 1. Spread the pieces of torn paper apart on the desk in front of you. 2. Rub the comb (or ruler) firmly with the woollen material for about 10 seconds. 3. Immediately hold the comb just above the pieces of paper, without touching them. What happens? There is a sample answer in the answer pages on page 27. The effect you have just observed is called a phenomenon (say FEN-OH-men-on). It is something that happens in the world around you that you can observe. When you think about more than one phenomenon, they are called phenomena. Here is another phenomenon that you may have noticed. Try it tonight, if you can. Do you have some clothes made from synthetic material that sometimes stick to your skin when you wear them or crackle when you take them off? Try putting the clothes on and rubbing them with your hands and arms. Then take them off in a dark room and shake them sharply. You will notice tiny sparks flicking and jumping all over your clothes! Introduction to electricity Set 1

21 3 Have you slid down a plastic slippery dip or walked across new carpet, then got a little electric shock when you touched something made from metal? These are all examples of phenomena that scientists call static electricity. Think about these examples. How are they all similar? How are the examples alike in the way that static electricity is caused? How are the examples alike in the observations that are made? Did you notice that each phenomenon is caused when something is rubbed? You rubbed the comb with woollen material, clothes rubbed your body, you rubbed against a slippery dip and your feet rubbed over carpet. Did you notice that, in each situation, things moved or were stuck together, or tiny sparks jumped? These are common features of static electricity. Static electricity involves objects becoming electrostatically charged. The charge stays on the object, without moving. That is why this kind of electricity is called static electricity; static means not moving or changing. Write a definition for static electricity. There is a sample answer in the answer pages. Static electricity isn t always static; it can move. The sparks you observed are electrical energy jumping from one place to another. Lightning is a really big example of electrical energy jumping through air. Introduction to electricity Set 1

22 4 What is electrical charge? Objects can gain an electrostatic charge when they are rubbed. Why? The easiest way to explain is to look at the parts of an atom. You probably remember that an atom is the smallest particle of matter that can exist on its own. Everything is made from atoms. Atoms are very, very small. About million atoms would cover the full stop at the end of this sentence. Atoms are usually pictured as very small balls. But inside each atom, there are even smaller particles. These particles that make up an atom can be represented in a diagram. Here is a diagram of an atom of an element called boron. electron neutron proton nucleus of atom (It is different from the nucleus of a living cell.) The boron atom is composed of electrons, neutrons and protons. 1. Which of these do you think has: (a) a positive electrostatic charge? (b) a negative electrostatic charge? (c) no electrostatic charge? Check your answers now. Did you notice that there are five protons and five electrons in this atom? This is important. The pluses and minuses can cancel each other out. So when there is an equal number of protons and electrons, the atom has no overall electrical charge. It is neutral, or uncharged. But what can happen if the atom is rubbed? Electrons from the outside of the atom can be rubbed off. Protons are not rubbed off. They stay in the nucleus of the atom. Introduction to electricity Set 1

23 5 Here is a diagram of an atom of boron that has lost some electrons. electron neutron proton 2. This atom has an overall electrical charge. Would it be a positive charge or a negative charge? Why? 3. The electrons that were rubbed off this atom became stuck to another atom. Do you think that that other atom would now be positively charged or negatively charged? Why? Please check your answers. You have seen that there are two kinds of electrical charge positive charge and negative charge. Objects become charged when negative charges called electrons move from one object to another. And electrons can be moved when objects rub together. 4. Complete the sentences below to make a summary about electrical charges and static electricity. Static electricity describes that occur when objects have extra electrical. This electrical charge may be or. Objects become charged when electrons are onto or off atoms in the objects. Check your answers now. Introduction to electricity Set 1

24 6 Another example Static electricity, also called electrostatics, was studied a lot in the 1800s. Scientists discovered a material (rubber mixed with molten sulfur) called ebonite that easily becomes electrostatically charged. Ebonite looks like the black keys on an old piano. Scientists make it into sticks about 30 cm long and 1 cm in diameter, which are called ebonite rods. When ebonite is rubbed with woollen material (often called flannel), ebonite becomes negatively charged. 1. Label the ebonite rod and flannel in the diagram below. 2. Put some minus signs ( ) on the ebonite rod to show that it is negatively charged. 3. What have been rubbed onto the ebonite rod to give it a negative charge? 4. Where did these electrons come from? 5. Since atoms in the flannel have lost electrons, what is the electrical charge on the flannel? 6. Put some plus signs (+) on the flannel to show that it is positively charged. (How many plus signs should you use? The same number as the number of minus signs that you drew onto the ebonite rod.) If you d like to check your diagram, turn to the answer pages. Introduction to electricity Set 1

25 7 plate A device called an electroscope, that detects electrostatically charged objects, was developed in the late 1700s. The vane in the electroscope moves when a charged object touches or comes near its plate. vane What happens when an ebonite rod touches or comes near the plate of an electroscope? negatively charged ebonite rod 7. Write a sentence about what you observe from this diagram. electroscope Compare your sentence with the one in the answer pages. Scientists also found that the electroscope vane moved when a wire was used to join the charged rod and plate. wire 8. Suggest an explanation for what is happening. Introduction to electricity Set 1

26 8 Did you think that electrons must be travelling through the wire from the ebonite rod to the electroscope? Well done if you did, because that is what scientists thought too. So electrical charges can be made to travel through a wire. And when they do, scientists say that an electric current is flowing. Scientists used the term dynamic electricity to describe phenomena that involved these moving electrical charges. People still talk about static electricity. For most people, it is more of a nuisance than a help. But dynamic electricity, what we commonly think of as electricity, has become vital in our modern world. Almost everything you do and have has involved electricity in some way. 9. Complete the sentences below to make a summary about electric current and dynamic electricity. Dynamic electricity describes that occur when electrical charges move through a. The electrical charges are. An electric is produced when electrons travel through a wire. Check your answers now. Have you noticed that the adjectives (describing words) electric, electrical and electrostatic have been used to describe objects and charges in this lesson? You'll see these words often in this unit about electricity! In most situations, you can use the words electric and electrical to replace each other. Electrostatic can also be used to mean electric or electrical when you are talking or writing about static electricity. Electrostatic is seldom used when you consider moving, or dynamic, electricity. Exercise 1 How scientific do you think your ideas about electricity were at the beginning of the lesson? Have any of your ideas about electricity changed? In send-in Exercise 1, you will make another concept map about electricity. Please complete this exercise now. Introduction to electricity Set 1

27 9 Lessons 2 and 3 Investigating static electricity In these lessons, you will investigate some more examples of phenomena caused by static electricity. Remember, these are caused by a build-up, or accumulation, of electrical charge on an object. This electrical charge can be either positive or negative. Some party tricks Static electricity is fun to use in tricks. As you perform the tricks described, think about what they tell you about electrostatically charged objects. A charged object near an uncharged object What happens when an electrostatically charged object is placed near an uncharged object? You have already begun to investigate this question, when you put a charged comb near some neutral, or uncharged, pieces of paper. Here are some more activities to do and consider. For these activities, you will need: a balloon some woollen fabric (or a woollen jumper) a plastic ruler or a plastic teaspoon running water from a tap. What to do: 1. Inflate (blow up) the balloon to normal size and knot it. Stretch out your arm and put the balloon under it. What happens?? I hope that wasn t a surprise! You would expect the balloon to fall to the floor, right? Introduction to electricity Set 1

28 10 2. Rub the balloon vigorously all over with the woollen material. (It is often easiest to put on a woollen jumper then rub the balloon against you.) Do you think the balloon has become electrically charged? Why? The balloon may have become electrically charged because rubbing can cause charge to accumulate (build up) on an object. 3. Try the test again. What happens?? 4. Now put the charged balloon near your hair. What happens? If it is a dry day, you can make the charged balloon attract many light objects and stick in lots of places. (The day needs to be dry because water in the air can steal electrical charge from the balloon.) 5. Now take one of your plastic objects; I will call it a ruler. Go to a tap and start the water running very gently so that it makes a thin stream. 6. Charge the ruler by rubbing it with your woollen material for about 10 seconds. Then put it beside (not in) Draw what happens to the water. the stream of water. kitchen tap hold charged object here thin stream of water charged object Look in the answer pages. Introduction to electricity Set 1

29 11 Here again is the question that you have been investigating. What can happen when an electrostatically charged object is placed near an uncharged object? Write a general answer for this question. There is a sample answer in the answer pages. A charged object near another object with the same charge What happens when an electrostatically charged object is placed near another object that has the same electrical charge? Here are some activities to do and consider. For these activities, you will need: some woollen fabric (or a woollen jumper) 2 stick-shaped objects made from the same kind of plastic; for example, two plastic combs, plastic rulers or plastic teaspoons a tiny piece of torn paper, smaller than 1 cm in any direction a clock glass or a flattened plastic bottle such as a shampoo bottle. What to do: 1. Balance one ruler (or spoon) across a clock glass (or plastic bottle) so that the ruler can spin easily. Here are two ways you could make it balance. 2. What do you predict would happen if you brought a charged object near the end of the ruler across the clock glass? Introduction to electricity Set 1

30 12 3. Charge the other ruler and test your prediction. What happens? charged ruler uncharged ruler clock glass You know that an electrically charged object can attract a neutral, or uncharged, object so you should have observed that the uncharged ruler moved towards the charged one. 4. Repeat the activity but this time make both rulers charged. (Rub one ruler and balance it on the clock glass. Then rub the other ruler and put it beside the rubbed end of the balanced ruler.) What happens? If you did not observe that the charged objects move apart, try Step 4 again. 5. Now I d like you to look more closely at the first activity you did in this unit. Rub your plastic object to make it charged. Pick up the scrap of paper by attracting it with the charged object. Watch the piece of paper until something happens. What happens? Attract the piece of paper again and see if the same thing happens. You can do it over and over. How can you explain this phenomenon? Introduction to electricity Set 1

31 13 6. Here is an explanation but the sentences in it have been jumbled. Number them from 1 to 7 to make the correct order. The charged comb attracts the neutral paper. The comb and the paper share the electrical charge. The comb becomes electrostatically charged when it is rubbed. The paper drops off the comb onto the table. The paper now has the same electrical charge as the comb. The paper moves towards the comb and sticks to it. The paper moves away from the comb because they both have the same electrical charge. Turn to the answer pages to check your answer. Two charged objects move apart if they both have the same electrical charge. Scientists say that they repel each other. Two negatively charged objects will push each other apart. So will two positively charged objects. Like charges repel. But what happens if the objects have different charges? A positively charged object near a negatively charged object Positive and negative are called opposites of each other. So if one object is positively charged and the other is negatively charged, you can say that the objects have opposite charges. When two opposite charges are near each other, they move towards each other. They are pulled together, or attracted. Opposite charges attract. It is hard for you to do an activity at home to test opposite charges because most things in your home become positively charged when you rub them. If you attend a minischool, you may be able to perform some investigations using the scientific equipment described on the next page. If you are particularly interested, contact your teacher. You teacher may help you to plan a student research project about static electricity. Introduction to electricity Set 1

32 14 A summary using scientific equipment On page 17, there are diagrams about the following situations. Cut out the diagrams and match them with the descriptions. When an ebonite rod is rubbed with flannel, the ebonite rod becomes negatively charged (and the flannel becomes positively charged). When a plastic rod called a perspex rod is rubbed with fabric called silk, the perspex rod becomes positively charged (and the silk becomes negatively charged). When a charged rod touches an uncharged, or neutral, electroscope, charge is shared between the rod and the electroscope. The electroscope becomes charged too. Introduction to electricity Set 1

33 15 When two rods with opposite electrostatic charge are brought close together, they attract each other and move together. When two rods with the same electrostatic charge are brought close together, they repel each other and move apart. Introduction to electricity Set 1

34 16 A charged rod will attract a neutral, or uncharged, object. Look again at the two descriptions and diagrams on page 14. They present information about one main idea in electrostatics. (Electrostatics is the study of static electricity.) Find the box on page 17 that contains a heading about this main idea. Cut out the box and put it into the space above the descriptions and diagrams on page 14. Then find the heading for the two descriptions and diagrams on page 15. The remaining heading should match the description and diagram on this page. Finally, look at all the diagrams again and decide which rods will move. Draw an arrow to show the direction that each rod moves. Would you like to check your answers? Look in the answer pages. Use sticky tape or glue to secure the headings and diagrams into their correct places. Exercises 2.1 and 2.2 You will need to use information and ways of writing about electrostatically charged objects to complete these send-in exercises. Introduction to electricity Set 1

35 17 Use the diagrams and headings below to complete pages 14 to 16. flannel ebonite rod neutral ebonite rod + silk perspex rod charged ebonite rod electroscope electroscope charged vane charged perspex rod charged ebonite rod clock glass charged perspex rod clock glass charged perspex rod charged perspex rod clock glass Ways to make an object electrostatically charged How objects with electrostatic charge affect each other How electrostatically charged objects affect neutral objects Introduction to electricity Set 1

36 18 Introduction to electricity Set 1

37 19 Lesson 4 Energy transformations Have you ever played with a transformer toy? What does it do? When scientists talk about energy transformations, they mean that energy changes from one form of energy into another. Just as all the parts of the transformer toy are still there after it has changed from one toy into another, all the energy still exists after it changes form. What energy transformations have you seen so far in this unit? Giving an object an electrostatic charge When you rubbed the object to make it charged, what form of energy were you using? Underline the best answer. electrical heat sound kinetic light potential nuclear Rubbing is movement, so I think kinetic is the best answer. Did you? What form of energy did your kinetic energy become? Underline the best answer. electrical heat sound kinetic light potential nuclear If you connected the electrostatic charge on the object with electrical energy, you are right! Energy transformations using dynamic electricity In Lesson 1, you learned about how electrical charges can move through wire. And when they do, an electric current is produced. This is an example of dynamic, or moving, electricity. Many of the energy transformations that we use in everyday life involve dynamic electricity. Let s consider some examples. Introduction to electricity Set 1

38 20 A simple circuit You ll learn about what a circuit is in Set 2. For the moment, concentrate on using information you already understand to solve some problems about energy transformations. Here is a diagram of a simple circuit. Electric current can travel through the wires in the circuit. globes giving out light energy and some heat energy battery with chemical energy wire In the battery, chemical energy is transformed into electrical energy. The electric current through the wire carries electrical energy from the battery to the other parts of the circuit. The current isn t used up in the circuit or changed into anything else. It is the electrical energy that is changed into other forms of energy. In the light globes in this circuit, electrical energy is changed into heat energy then light energy. When the metal filament is hot enough light energy is given out. You can show the energy transformations in a simple equation. chemical energy Æ electrical energy Æ light energy Æ heat energy This equation means that chemical energy is changed, or transformed, into electrical energy. Then electrical energy is changed into heat and light. It s easier to read as an equation, isn t it! Now it s your turn to look at some energy transformations that occur in appliances in your home. Introduction to electricity Set 1

39 21 Examples of energy transformations in electrical appliances When you plug in and switch on an appliance, an electric current flows through the appliance. This current carries electrical energy to the appliance. In the appliance, electrical energy is changed into other forms of energy. You are going to look at some common appliances and deduce the energy transformations that happen in each appliance. First think about a television. What energy transformations happen here? Did you say that electrical energy is changed into light energy and sound energy? Write these transformations as a simple equation. The answer is at the bottom of the page. Because they are all forms of energy, you can leave the word energy out of the equation. So your equation becomes: electrical Æ light + sound Consider another appliance an electric fan. Write an equation for the energy transformations that occur in it. If you d like to check your answer, turn to the answer pages. Here is the equation for the transformations of energy in a television. electrical energy Æ light energy + sound energy Introduction to electricity Set 1

40 22 The table below lists some appliances that you may have in your home. Fill in the table by adding an equation for the energy transformations that occur in each device. (You have already done the first two answers on page 21 so I have filled them in for you.) Appliance television electric fan Energy transformations electrical Æ light + sound electrical Æ kinetic radio electric stove element electric jug CD player computer Check your answers in the answer pages. If you do not get the same answers, discuss the transformations with a friend or family member. Talking about the change usually helps you to see the problem more clearly. If you still cannot understand the answers in the answer pages, contact your teacher. In this lesson, you thought about situations and devices that involve electrical energy. You recalled that electrical energy is very useful when it can be changed, or transformed, into other forms of energy. You have summarised energy transformations in common situations by writing simple equations. Exercise 4 In send-in Exercise 4, you will identify some common objects that use electrical energy and write simple equations for the energy transformations that occur in these appliances. Please complete this exercise now. Introduction to electricity Set 1

41 23 Lesson 5 Getting ready for Set 2 Now that you have a better understanding of what electricity is, you are ready to build a tester that can show when an electric current is flowing. You will need parts from a simple electronics kit such as those supplied by Dick Smith or Jaycar stores. Don't panic! You don't need to be an expert in electronics. (Electronics is the technology and science of using electric currents for making, sending, receiving and storing information.) You are going to learn all you need as you progress through the unit. Sorting out your electronics equipment Before you do anything, you should know that one of the assessment items for this unit involves returning your equipment after you have used it. You will need to be organised in how you unpack the kit if you are to pack up well. On the next page is the heading Checklist. The first five items, or components, on the checklist are: battery board bag of springs and clips (or screws and washers) silver-coloured wire two plastic-coated wires with alligator clips. Alligator clips have teeth like alligators or crocodiles. Most of the alligator clips are hidden by a plastic cover. All that you can see of them is some silver teeth sticking out of the end of the plastic. Find these five items. As you identify each item, put a tick in the box next to its name in the checklist on the next page. Introduction to electricity Set 1

42 24 Checklist battery board bag of springs and clips (or screws and washers) silver-coloured wire two plastic-coated wires with alligator clips screwdriver battery clip LED (light emitting diode) protection diode 390 ohm resistor You should have five or six items left on the checklist to identify. What to do next Do you need a screwdriver? You need one if you have screws and washers. Tick this item in the checklist if you have one. Now find the battery clip. It has two plastic coated wires joined to it, one red and one black. The battery clip looks like this. When you identify the battery clip, put a tick in the box next to its name in the checklist. Introduction to electricity Set 1

43 25 Find the LED (say L-E-D). The LED looks like a little plastic light globe with two wire legs. LEDs are usually red but can be other colours such as yellow or green. When you have found the LED, put a tick in the box next to their name in the checklist. A protection diode looks like a black plastic cylinder with a wire sticking out each end. There should be a silver-coloured band near one end of the cylinder. A protection diode looks like this. When you have identified the protection diode, put a tick in the box next to its name in the checklist. Resistors are small parts that resist the flow of electricity. Coloured bands on a resistor use a code to show the size of its electrical resistance. The colours of the bands on 390 ohm resistors are usually, in order, orange, white, brown and gold. When you have identified the resistor, put a tick in the box next to its name in the checklist. If you think that you can look at each item of equipment and remember its name, go on to the next section on the next page. If you don't think you are ready to do a test, go over this section again, then do the test. Introduction to electricity Set 1

44 26 Test yourself This test has been put in to help you. Don't be tempted to leave it out. Without looking at the first part of this lesson, pick up any item and tick in the box to show than you can identify the item. Keep going until you have identified all the items in the kit. If you discover that you can't identify all the items, go through this lesson again then test yourself. When you have mastered this knowledge, you are ready to start making your tester. You can say that you have mastered this knowledge when you get 100% on the mastery test. Mastery test checklist battery board bag of springs and clips (or screws and washers) silver-coloured wire two plastic-coated wires with alligator clips screwdriver (if you have screws and washers) battery clip LED protection diode 390 ohm resistor (orange white brown gold bands) Introduction to electricity Set 1

45 Suggested answers 27 Lesson 1 What is electricity? Page 2 3. The pieces of paper jumped up and stuck to the comb. You may even have seen some pieces of paper hanging from other pieces that were clinging to the charged plastic. Page 3 Static electricity refers to phenomena that occur when objects become electrostatically charged. What is electrical charge? Page 4 1. (a) proton (because it has a plus sign on it) (b) electron (because it has a minus sign on it) (c) neutron (because it has no sign on it; it is the only one left) Page 5 2. The boron atom would have a positive charge because it has lost two electrons. (It has more protons [positives] than electrons [negatives].) 3. The other atom would be negatively charged because it has gained two extra electrons. (It will have more electrons [negatives] than protons [positives].) 4. Static electricity describes phenomena that occur when objects have extra electrical charge. This electrical charge may be positive or negative. Objects become charged when electrons are rubbed onto or off atoms in the objects. Another example Page 6 + ebonite rod flannel Introduction to electricity Set 1

46 28 Lesson 1 continued Page 7 7. The vane in the electroscope moved when the plate of the electroscope was touched with the ebonite rod. Page 8 9. Dynamic electricity describes phenomena that occur when electrical charges move through a wire. The electrical charges are electrons. An electric current is produced when electrons travel through a wire. Lessons 2 and 3 Investigating static electricity A charged object near an uncharged object Page 10 charged object The stream of water bends towards the charged object. Page 11 An uncharged object can move towards a nearby electrostatically charged object. A charged object near another object with the same charge Page Here is the best order for the explanation The charged comb attracts the neutral paper. The comb and the paper share the electrical charge. The comb becomes electrostatically charged when it is rubbed. The paper drops off the comb onto the table. The paper now has the same electrical charge as the comb. The paper moves towards the comb and sticks to it. The paper moves away from the comb because they both have the same electrical charge. Introduction to electricity Set 1

47 29 Lessons 2 and 3 continued A summary using scientific equipment Page 14 Ways to make an object electrostatically charged Top diagram Bottom diagram flannel ebonite rod charged ebonite rod electroscope + silk perspex rod electroscope charged vane Page 15 How objects with electrostatic charge affect each other Top diagram Bottom diagram charged ebonite rod charged perspex rod charged perspex rod clock glass charged perspex rod clock glass Introduction to electricity Set 1

48 30 Lessons 2 and 3 continued Page 16 How electrostatically charged objects affect neutral objects charged perspex rod neutral ebonite rod clock glass Lesson 4 Energy transformations Examples of energy transformations in electrical appliances Page 21 electrical Æ kinetic + sound or electrical Æ kinetic How did I get this answer? Parts of the fan move when the fan is switched on. Moving energy is called kinetic energy. You might have heard a noise, or sound energy, when the fan is switched on. Most electrical fans make noise (sound energy) but it is often left out of an equation summarising the energy transformations because it isn t a useful form of energy when it comes from a fan. It is more of a nuisance. Page 22 Here is the completed table. Appliance radio electric stove element electric jug CD player computer Energy transformations electrical Æ sound electrical Æ heat + light electrical Æ heat + sound electrical Æ sound electrical Æ light + sound Introduction to electricity Set 1

49 31 Send-in page Name Lesson 1: What is electricity? Exercise 1 In the space below, draw a concept map about electricity. It does not need to be very complicated but it must include these terms. dynamic electric current negative spark electrons electrical charge positive static You can add other words if you like. Then draw lines to link the terms to the word electricity or to each other, if you can. Label each line with the reason that you think the terms are linked. electricity Introduction to electricity Set 1

50 32 Introduction to electricity Set 1

51 33 Send-in page Name Lessons 2 & 3: Investigating static electricity Exercise 2.1 Here is a description of an activity that you have done. A comb was rubbed firmly with flannel. Then the comb was held near a small scrap of paper. The paper jumped up and stuck onto the comb. After a short while, the paper dropped off the comb onto the table. 1. There are two places in this description where objects become electrostatically charged. Underline them. (Do not underline everything! Underline as few words as possible.) 2. (a) Label your first underlining, A. Describe how the object has gained its electrostatic charge. (b) Label your second underlining, B. Describe how this object has gained its electrostatic charge. 3. Rewrite the last two sentences of the description in your own words. Use the words repelled and attracted in your sentences. Introduction to electricity Set 1

52 34 Exercise 2.2 Complete the sentences below to describe how the electrostatically charged objects in the diagrams are affecting each other. charged ebonite rod charged ebonite rod clock glass These charged rods move each other because they have electrostatic charge. charged ebonite rod charged perspex rod clock glass These charged rods move Introduction to electricity Set 1

53 35 Send-in page Name Lesson 4: Energy transformations Exercise 4 Here is a photograph of a corner of a family's living room. Which things in this photograph need electrical energy to operate? Choose two of them and write an equation for the energy transformations that occur in each appliance. Name of appliance Equation for energy transformations Introduction to electricity Set 1

54 36 Introduction to electricity Set 1

55 Science Stage 4 NEW SOUTH WALES DEPARTMENT OF EDUCATION AND TRAINING Introduction to electricity Set 2: Making an electrical circuit 1 5 K 6 A 9 V K 9 A V 10 K A 16 K A 14 15

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57 Introduction to electricity i The hand points to the names of the lessons in this set. Set Set 1 2 Set 3 Finding out about electricity Lesson 1 What is electricity? Lessons 2 and 3 Investigating static electricity Lesson 4 Energy transformations Lesson 5 Getting ready for Set 2 Making an electrical circuit Lessons 6 to 8 Making a tester Lesson 9 Resistor coding and decoding Lesson 10 What is an electrical circuit? Investigating electrical circuits Lessons 11 and 12 Energy for a circuit Lesson 13 Diagrams for circuits Lesson 14 Predicting Lesson 15 Investigating Introduction to electrcity Set 2

58 ii Set 2: Making an electrical circuit Contents What will you learn in Set 2?... iii What do you need for Set 2?... iv Lessons 6 to 8 Making a tester... 1 Lesson 9 Resistor coding and decoding Lesson 10 What is an electrical circuit? Suggested answers Send-in pages Introduction to electrcity Set 2

59 What will you learn in Set 2? iii In Set 2, you will have opportunities to achieve and demonstrate the following statements. follow instructions to make a tester evaluate what you have learned by making the tester use the resistor code and carry out decoding use a model to describe an electrical circuit state that an electric current can flow in an electrical circuit that has a battery (or source of electrical energy) describe an electric current as a flow of electrical charge (electrons) around an electrical circuit Introduction to electrcity Set 2

60 iv What do you need for Set 2? Here is a reminder of the items you need for Set 2. Lessons 6 to 8 battery board 8 springs and clips (or screws and washers) silver-coloured wire 2 plastic-coated wires with alligator clips screwdriver (if you have screws and washers) battery clip a protection diode a 390 ohm resistor (orange, white, brown and gold bands) a LED. Introduction to electrcity Set 2

61 1 Lessons 6 to 8 Making a tester These three lessons have been set aside for you to make the tester. Some people will need longer than this, while others will finish in less time. The instructions haven't been broken up into separate lessons because I've found that many students want to keep going once they get started on something like this. You are free to organise your own time as long as you get the tester made. Before you start to make the tester, turn to Exercise 6 in the send-in pages. There is a section of Exercise 6 for you to complete and a section to be filled in by a person who will observe your work. This observer could be a teacher, parent, friend or another student. Only two marks are given for making a tester that works. The other marks are given for your organisation and how you work. Before you start putting the components together, you need to know that you won't use all the parts you have been given in the electronics kit. There are some spares so don't worry if you have some parts left over. You should have components left. You can use some of them if you want to put together other electronic equipment. Components The components you need for the tester are: battery board 8 springs and clips (or screws and washers) silver-coloured wire 2 plastic-coated wires with alligator clips screwdriver (if you have screws and washers) battery clip 1 protection diode ohm resistor (orange, white, brown and gold bands) 1 LED. Follow the instructions, step-by-step. Introduction to electricity Set 2

62 2 1. Using the tester layout diagram and board The layout diagram is the guide you will use as you build the tester. Cut out the diagram from page 9. Match the holes in the board from your kit with the dots on the layout diagram. Sticky tape the layout diagram onto the board. If something goes wrong and you need another diagram, you can trace over any of the diagrams from the following pages. All you need is the outline and the numbered dots. 2. Using the springs and clips (or screws and washers) These try to roll away so put them into a saucer or some kind of container or you might spend half the day chasing them. There are eight numbered dots on the layout diagram. Use a pencil to push a hole through the paper layout diagram at each dot If you have springs and clips, fit each spring over a clip. Then squeeze the bottom of each clip and push it into the hole at a dot. The clip will click into place. If you have screws and washers, put one screw and washer into each dot. You should have some screws and washers left over. Don't worry if your washers are different sizes. This does not matter. spring bottom of clip Introduction to electricity Set 2

63 3 board washer screw screw washer board Don't put the screws in too tightly. Later on, you will tuck the connecting wires and the component wires under the washers before you tighten the screws. 3. Using the connecting wires These connecting wires are cut from the silver-coloured wire in your kit. If you need to cut the wires to fit, you can use pliers or an old pair of scissors. Don't cut wire with new scissors; this would damage them. You need two pieces of connecting wire; wire one to go from dot one to dot eight, and wire two to go from dot three, around dot four and along to dot five. Make sure that the wires are long enough to be tucked into the tops of the clips (or under the washers) at each end. It is safer to have the wires a bit longer rather than too short. You can always trim a bit off a wire but you can t stick a bit back on if you find that the wire is too short Introduction to electricity Set 2

64 4 If you have springs and clips, push the spring at dot one down so that you can put the end of the wire through the loop at the top of the clip. When you let go of the spring, the wire will be held in place. If you have screws and washers, sit the wires in place, with their ends tucked under the washers. You can tighten both the screw at dot four and the screw at dot eight now. 4. Using the battery clip The next thing to put in is the battery clip. Find the battery clip in your kit but don't put the battery into the clip yet. You can see that the battery clip has two plastic-coated wires coming from it, one red and one black. There should be a little bit of bare wire at the end of each of these plastic-coated wires. Tuck the bare end of the black wire into the clip (or under the washer) at dot five. Tuck the bare end of the red wire into the clip (or under the washer) at dot six. Make sure that the end of the silver-coloured connecting wire is still tucked into the same clip (or under the same washer) red 3 black 4 5 If you are using screws and washers, you can tighten the screw at dot five now. Before you leave this screw, check that none of the black plastic is tucked under the washer. Introduction to electricity Set 2

65 5 5. Using the protection diode Now you will put in the protection diode. A diode is a component that lets electric current move through in one direction only. Find one of the protection diodes in your kit. You can see that the protection diode has a wire coming out from each end, and a silver band near one end. Find the end with the silver band. This is called the K end of the diode. Tuck the wire from this end into the clip (or under the washer) at dot seven. (Tighten the screw if you have one.) Now tuck the wire from the other end of the protection diode into the clip (or under the washer) at dot six. Check that the bare end of the red wire from the battery clip is still tucked into this clip (or under this washer then tighten the screw) Introduction to electricity Set 2

66 6 6. Using the resistor Pick up the 390 ohm resistor. It has orange, white, brown and gold colour bands. This resistor controls the amount of electric current in a circuit by providing 390 ohms of electrical resistance. orange white brown gold The colour code is black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, purple 7, grey 8 and white 9. The first two bands, orange and white, stand for 39. The third band, brown, gives the number (1) of zeros. This indicates the resistance is 390 ohms. At the other end the gold band colour shows this is accurate to 5% : % ohms. Choose one end of the resistor. Resistors don't have to be put in in any particular direction, so it doesn't matter which end you choose The resistor goes between dots one and two. Tuck the wire from your chosen end of the resistor into the clip (or under the washer) at dot one. Check that the wire at the other end of the resistor will reach dot two but won't touch the clip (or washer) at dot three. If you have screws and washers, tighten the screw at dot one. Introduction to electricity Set 2

67 7 7. Using the LED Pick up the LED. It looks like a little red light globe with two stiff wire legs. red plastic leg LED is short for light emitting diode. Emitting means giving out. The LED gives out light only when electric current goes through it. Like the protection diode, the LED has to go into the tester the right way around. The LED has a rim at the bottom (wire) end of the plastic. It looks as if one part of the rim has been cut off. This side of the LED is called the K side. It might be easier to find this side by feeling rather than by looking. The wire leg on this side is usually shorter than the other leg. The LED goes in between dots two and three. The wire from the K side of the LED goes to dot three. The other wire from the LED goes to dot two. If the LED is new, you will need to bend its legs. Tuck the wire from the K side of the LED into the clip (or under the washer) at dot three. Make sure that the end of the connecting wire is still tucked into the clip (or under the washer then tighten the screw at dot three). Tuck the wire from the other (whole rim) side of the LED into the clip (or under the washer) at dot two. Check that the wire from the resistor is still tucked into the same clip (or under the same washer then tighten the screw at dot two). Introduction to electricity Set 2

68 8 8. Using the battery Now push your battery terminals into the battery clip. You can see that there is only one way to do this. You might have to press hard as the clips are sometimes stiff when they are new. 9. Using the probes The two wires you have with alligator clips at each end are going to be your probes. You should have a gap between dots seven and eight Pick up one of these wires and clip one of its ends onto the clip (or screw) at dot seven. Pick up the other wire and clip one of its ends onto the clip (or screw) at dot eight. Introduction to electricity Set 2

69 9 10. Does it work? Before you try the tester, make sure that nothing has come loose. At the end of each of your probes, you should have an alligator clip which is not connected to anything. Touch these two free alligator clips together. If everything is right, the LED lights up. If the LED lights up, show your supervisor and ask your supervisor to fill in the Supervisor s evaluation in Exercise 6. Don't pull your tester apart because you will need it again in Set 3. If the LED doesn't light up, check your tester by making sure every part has: been correctly positioned and is the correct way around metal to metal contact so that electricity can flow between the parts. Exercise 6 Once you have finished making your tester, complete your section of Exercise 6 in the send-in pages. (Be sure to ask your observer to complete the other section of Exercise 6.) Cut around the layout diagram below and attach it to your board Introduction to electricity Set 2

70 10 Introduction to electricity Set 2

71 11 Lesson 9 Resistor coding and decoding What is a resistor? A resistor is a component in an electrical circuit that opposes, or resists, the flow of electric current through the circuit. When this happens, electrical energy is changed into another form of energy, such as light or heat. Some resistors are made from materials that change much of the electrical energy into other forms. These resistors have a large value of a property called resistance. Other resistors let most of the electric current travel through; they have low resistance because they do not oppose the electric current very much. Electrical resistance in measured in units called ohms. The symbol for ohm is a Greek letter called omega, W. What is the resistor colour code? Here is the list of colours and the number each stands for. Colour Number black 0 brown 1 red 2 orange 3 yellow 4 green 5 blue 6 purple 7 grey 8 white 9 A gold (5%) or silver (10%) tolerance band shows how close the actual resistance is to the size shown by the colour bands. Introduction to electricity Set 2

72 12 Using the resistor colour code Decoding involves changing colours to numbers The colours on this resistor are orange, white and brown. white brown orange gold You can ignore the gold band showing 5% tolerance. Step 1 Write the colours in the same order as they appear on the resistor. Colours orange white brown Numbers Step 2 Write the number value that each colour stands for Colours orange white brown Numbers Step 3 The first two numbers are the first two numbers of the resistor value. In this example, 3 and 9. The third number tells how many zeros to write after the first two numbers. In this example, the third number is 1, so write one zero after the first two numbers. This gives 390 ohms (390 W). Introduction to electricity Set 2

73 13 Your turn at using the resistor code Here are four decoding practice items for you. 1. Colours yellow orange red Numbers Resistor value = ohms 2. Colours brown grey blue Numbers Resistor value = 3. Colours blue red green Numbers Resistor value = 4. Colours purple green black Numbers Resistor value = Please check your answers. Introduction to electricity Set 2

74 14 Coding involves changing numbers to colours Example 1: Resistor value = ohms Fill the information into a table. Numbers (zeros) Colours Numbers (zeros) Colours grey red orange Example 2: Resistor value = ohms Numbers (zeros) Colours green brown yellow Your turn at coding Here are four practice items for you. 1. Resistor value = ohms Numbers Colours 2. Resistor value = ohms Numbers Colours Introduction to electricity Set 2

75 15 3. Resistor value = ohms Numbers Colours 4. Resistor value = 91 ohms Numbers Colours Have you checked your answers? Mastery test You need to use the resistor colour code sheet on the first page of this lesson when you do the test. 1. What is the resistor value if the coloured bands are: (a) Colours red yellow orange Numbers Resistor value = (b) Colours brown black brown Numbers Resistor value = Introduction to electricity Set 2

76 16 (c) Colours yellow purple black Numbers Resistor value = 2. What coloured bands can be used to represent a resistor value of: (a) 130 ohms? Numbers Colours (b) ohms? Numbers Colours (c) ohms? Numbers Colours Check your answers before you continue. Exercise 9 Exercise 9 gives you additional practice in decoding and coding using the resistor colour code. Introduction to electricity Set 2

77 17 Lesson 10 What is an electrical circuit? In this lesson, you are going to look at two types of circuits: racing circuits and electrical circuits. You are going to use what you know about racing circuits to help you get a clear idea of what an electrical circuit is. Then you will learn about what happens in an electrical circuit. Racing circuits Let's look at the everyday meaning of the word circuit. One meaning is a loop, complete round or course. You probably use this meaning for circuit when you talk about foot, bike or car racing circuits. Here is a student s map of the course for a cross country foot race. BOUNDARY STREET Malley s Scrub Duck Creek Park Hill Reed Swamp play equipment PARK ROAD 500 metres start here Does this racetrack fit with the definition of a circuit? Use a bright coloured texta or a highlighter to go over the dashed path of the racetrack on the map. Yes, you can see that the racetrack forms a loop or a complete round. The student runs around the pathway of the loop. Introduction to electricity Set 2

78 18 Have you heard of Australian car racing circuits, such as the Mt Panorama Circuit near Bathurst, NSW? There are motor bike races here each Easter and a major car race is held in October every year. Although the cars travel km in this race, the circuit is less than 10 km long. To finish the race, cars have to do more than 100 laps of the circuit, which means that the cars have to travel around the circuit more than 100 times. Now think about two other well known Australian races and decide if their paths or tracks can be called circuits. You may wish to get out your atlas or a map of Australia to help you. Sydney to Hobart yacht race The Sydney to Hobart yacht race begins each year on Boxing Day. The yachts start the race in Sydney and finish the race in Hobart. Does this path form a loop? Could you describe this path as a circuit? Yes or no? No, the path doesn't form a loop. Even though most of the yachts will come back to Sydney, the return trip is not part of the race so you can't call the path a circuit. Sydney to Melbourne ultramarathon The Sydney to Melbourne ultramarathon begins in Sydney and ends in Melbourne. Could you describe the path as a circuit? Why? Check your answer in the answer pages. Introduction to electricity Set 2

79 19 Some other racing circuits Here are sketches of four racetracks Which of these racetracks can be called circuits? Did you choose tracks two and four? Both of them can be called circuits because they form loops. A car (or horse or person whatever is racing) follows the pathway around in a loop. The beginning and the end are joined together. You may be wondering what racetracks have to do with this unit! Well, the tester that you made last lesson is an example of a circuit. (You ll understand better why it is a circuit when you have completed this lesson.) The idea of a circuit being a loop is used in science as well as in racing. In science, circuit refers to an electrical circuit (or an electric circuit). In an electrical circuit, electrical charges travel around the circuit. (Or you can say, electric current travels around an electrical circuit.) Introduction to electricity Set 2

80 20 Electrical circuits Now you are going to look at some sketches of science equipment and decide if any of the sketches show an electrical circuit. The circuit must be a loop made using components. Look at the four sketches below. 1 wire V battery wire wire lamp 1.5 V battery wire wire lamp V battery wire lamp V battery wire wire lamp What are the components in each box? Each sketch shows a battery, a lamp and some wires. Which of these sketches shows a battery and a lamp joined up in a loop? In other words, which of the sketches shows a circuit? Did you write number four? This is the only one which shows a loop so it is the only one which can be called a circuit. Now look at the tester that you made. This is an example of a circuit. Let's see how the tester fits in with the definition of a circuit as a loop. Does the tester form a loop? Hint: Check between dots seven and eight. Introduction to electricity Set 2

81 21 Did you answer no? You may be surprised to discover that it doesn't form a loop unless the bare ends of the probes are touching each other. This means that you can call the tester a circuit only when the bare ends of the probes are touching each other. In your tester, what change can you see when the ends of the probes are touching each other? When the ends of the probes are touching each other, the LED lights up. This suggests that the LED lights up when it is part of a circuit. Assume that the same thing is true about the lamp in the sketches. If the lamp lights up when it is part of a circuit, which of the sketches shows a situation where the lamp could light up? Write the number of the sketch you have chosen. In Sketch 1, the lamp and the battery are not connected. In Sketches 2 and 3, the lamp and battery are connected but not in a loop. Sketch 4 is the only one showing the lamp and battery connected in a circuit so it is the only one which shows a situation where the lamp could light up. Comparing racing and electrical circuits A racing circuit like Mt Panorama is a track on which cars travel around and around. You can think of an electrical circuit as a track on which electrical charge travels around and around. Whenever electrical charge is travelling around a circuit, an electric current is flowing in the circuit. Electric currents are often compared with flowing water. When water is moving or flowing, you d say that there is a current; when water is still (as it may be in a pond or lake if there is no wind) you d say that there is no current. Only flowing water makes a water current; and only flowing electrical charge makes an electric current. Introduction to electricity Set 2

82 22 What are the parts of an electrical circuit? Have another look at your tester. You can see that it is made of components joined by wires. 1.5 V battery wire wire lamp Now have look at this sketch. It should look familiar. This sketch also shows two items joined by wires. From these two examples, it seems that an electrical circuit is made of components joined by wires. Here is a sketch of three lamps joined by wires. You can see that there is a complete loop or path so, according to the definition, this can be called a circuit. Now you are faced with another question: is it an electrical circuit? How can you decide? Use the idea of an electrical circuit that you have used throughout the lesson. An electrical circuit is a track or pathway which electrical charge travels around and around. Have another look at the sketch. Do you think that there is an electric current in the loop or circuit? Remember that a current is the name for a flow of electrical charge in a circuit. Is there anything in the circuit to supply electrical energy? There is nothing in this circuit to make electrical charge flow so there is no current in the circuit. Because no charge can flow, you can't call this loop of lamps an electrical circuit. What causes electrical charge to flow in an electric circuit? Have a look back at the two electrical circuits you are familiar with: your tester and the electrical circuit at the top of this page made up of a battery and a lamp joined by wires. Introduction to electricity Set 2

83 23 What is the component that is found in each of the electrical circuits but not in the sketch of three lamps joined by wires? Did you notice that both of the electrical circuits have a battery? The battery is the part which causes electrical charge to flow. What could you do to make the loop, containing three lamps joined by wires, into an electrical circuit? You have to add a component to make electrical charge flow. What would you add? I hope that you wrote battery as your answer. An electrical circuit is the name for the path of an electric current (or flow of electrical charge). Now you can say what an electrical circuit is made of: a battery (or other source of electrical energy) plus other components connected by wires making a complete path for the electric current. Before you go on to Set 3, I want to be sure that you have taken in all the information about electric current and electrical circuits. So, I have set you a mastery test. You need to get everything right in the mastery test before you go on to send-in Exercise 10, then Set 3. Read the mastery test now. This will let you know which areas you need to revise before you do the test. It is a good idea to spend at least ten minutes on revision before you start the mastery test. If you don't get everything right the first time you do the mastery test, you will need to revise the lessons then do the test again. You may find it easier to write your answers in pencil so you can rub out any wrong answers. The mastery test is on the next page. Introduction to electricity Set 2

84 24 Mastery test about circuits 1. An electric current is the name for a flow of. 2. In your tester, the causes electrical charge to flow. 3. An electrical circuit is the name for the path of an. 4. State one similarity and one difference between a racing circuit and an electrical circuit. Similarity: Difference: 5. An electrical circuit must contain at least two parts. They are: 6. Using pencil, draw wires to complete these electrical circuits. 1.5 V battery 1.5 V battery Now check your answers. If any of your answers were wrong, rub them out. If you didn't get all of the answers right, go over Lesson 10 before you do the test again. Remember that you need to get the test 100% right before you go on. Exercise 10 Please complete this send-in exercise now. Introduction to electricity Set 2

85 Suggested answers 25 Lesson 9 Resistor coding and decoding Your turn at using the resistor code Page Colours yellow orange red Numbers Resistor value = ohms 2. Colours brown grey blue Numbers Resistor value = ohms 3. Colours blue red green Numbers Resistor value = ohms 4. Colours purple green black Numbers Resistor value = 75 ohms Introduction to electricity Set 2

86 26 Lesson 9 Resistor coding and decoding Your turn at coding Page Resistor value = ohms Numbers Colours orange white orange 2. Resistor value = ohms Numbers Colours blue grey yellow Page Resistor value = ohms Numbers Colours red purple red 4. Resistor value = 91 ohms Numbers Colours white brown black Mastery test Page (a) ohms (b) 100 ohms Page 16 (c) 47 ohms 2. (a) brown, orange, brown (1,3,1) (b) orange, blue, yellow (3,6,4) (c) green, blue, red (5,6,2) Introduction to electricity Set 2

87 27 Lesson 10 Page 18 What is an electrical circuit? Sydney to Melbourne ultramarathon The Sydney to Melbourne race is not a circuit because the path does not form a loop. The race does not start and end at the same place. Page 24 Mastery test about circuits 1. An electric current is the name for a flow of electrical charge. 2. In your tester, the battery causes electrical charge to flow. 3. An electrical circuit is the name for the path of an electric current. 4. Similarity: Both a racing circuit and an electrical circuit form a loop. Difference: Cars travel around a racing circuit but electrical charges (or electrons) move around an electrical circuit. An electrical circuit has an energy source as part of the circuit. 5. The parts of an electrical circuit are: a battery (or other source of electrical energy) components, such as resistors and lamps. (These are connected by wires.) 6. Here are the completed diagrams. 1.5 V battery 1.5 V battery Introduction to electricity Set 2

88 28 Introduction to electricity Set 2

89 29 Send-in page Name Lessons 6 to 8: Making a tester Exercise 6 Self evaluation What do you think you learned from this activity? Choose two of the statements below to complete. (You may complete more if you really want to.) I learned more about following instructions to perform an experiment because I learned more about solving problems that arise in an experiment because I learned that I enjoy finding out about things for myself because I learned about electrical circuits because Introduction to electricity Set 2

90 30 Observer's evaluation The guide below will help you work out how many marks to award. Please record the marks you select then add them up and write the total out of ten in the space given at the bottom of the page. Possible mark Mark awarded Organisation of work space during the activity good 2 average 1 poor /2 at the end of the activity good 2 average 1 poor /2 Instructions reads instructions 1 follows instructions 1 /2 Attitude to work keeps trying for a reasonable time 2 gives up easily 1 makes no effort at all 0 /2 Results it works 2 it doesn't work 1 /2 Total /10 Signature of observer: Introduction to electricity Set 2

91 31 Send-in page Name Lesson 9: Troubleshooting Exercise 9 1. What is the resistor value if the coloured bands are: (a) Colours yellow black brown Numbers Resistor value = (b) Colours purple white orange Numbers Resistor value = 2. What coloured bands can be used to represent a resistor value of: (a) 8500 ohms? Numbers Colours (b) 620 ohms? Numbers Colours Introduction to electricity Set 2

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93 33 Send-in page Name Lesson 10: What is an electrical circuit? Exercise 10 You may not have noticed it but, in this lesson, you have been using models to describe electrical energy. Use information from the lesson to answer questions about the models you have used. 1. What is the name of the pathway that electrical energy can move through? 2. What is this pathway like? (You can compare it with other courses if you like.) 3. What travels around the pathway, carrying electrical energy? 4. Describe an electric current. Introduction to electricity Set 2

94 34 Introduction to electricity Set 2

95 Science Stage 4 NEW SOUTH WALES DEPARTMENT OF EDUCATION AND TRAINING Introduction to electricity Set 3: Investigating electrical circuits 1 5 K 6 A 9 V K 9 A V 10 K A 16 K A 14 15

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97 Introduction to electricity i The hand points to the names of the lessons in this set. Set Set 1 Set 2 3 Finding out about electricity Lesson 1 What is electricity? Lessons 2 and 3 Investigating static electricity Lesson 4 Energy transformations Lesson 5 Getting ready for Set 2 Making an electrical circuit Lessons 6 to 8 Making a tester Lesson 9 Resistor coding and decoding Lesson 10 What is an electrical circuit? Investigating electrical circuits Lessons 11 and 12 Energy for a circuit Lesson 13 Diagrams for circuits Lesson 14 Predicting Lesson 15 Investigating Introduction to electricity Set 3

98 ii Set 3: Investigating electrical circuits Contents What will you learn in Set 3?... iii What do you need for Set 3?... iv Lessons 11 and 12 Energy for a circuit... 1 Lesson 13 Diagrams for circuits Lesson 14 Predicting Lesson 15 Investigating Suggested answers Send-in pages Introduction to electricity Set 3

99 What will you learn in Set 3? iii In Set 3, you will have opportunities to achieve and demonstrate the following statements. interpret information and build a model of an electrical cell describe the scientific meaning of the term battery identify some uses and the importance of batteries in our society suggest ways to reduce the use of batteries and so reduce their environmental impact identify and draw some common circuit symbols identify the direction that electric current flows around an electrical circuit identify components in an electrical circuit that will transform electrical energy into other forms of energy draw a circuit diagram for your tester outline how energy is transferred from a battery to other components in an electrical circuit make, test and compare predictions with observations about materials that can be part of an electrical circuit bring together ideas about electricity in explanations. Introduction to electricity Set 3

100 iv What do you need for Set 3? Here is a reminder of the items you need for Set 3. To save time, it might be a good idea to get all these things ready before you start. Lessons 11 and 12 scissors sticky tape or glue Lesson 13 completed tester circuit from Set 2 scrap paper ruler sharp pencil Lesson 15 completed tester circuit from Set 2 ten materials from around your home Introduction to electricity Set 3

101 1 Lessons 11 and 12 Energy for a circuit An electrical circuit cannot function without an energy source such as a battery. In these lessons, you will investigate what a battery is, what it does and how batteries should be used responsibly. Inside a 1.5 volt battery A battery isn't a hollow container full of electrical energy, just waiting to jump out. A battery is full of chemicals. You can think about a battery as a place where a change happens where chemical energy is changed into electrical energy. You are not expected to learn any details about the chemicals or chemical changes that happen in a battery. If you are interested in finding out more about what happens inside a battery, you could find more information in books, CD-ROMs or from the Internet. In this section, you are going to make a model of the working parts of a 1.5 volt battery to give you a picture of what is inside a battery. It won't be a working model! What you will do is cut out the parts and use them to make a picture of what the inside of a battery looks like, when the battery has been cut in half from top to bottom. Your model won't include the outside of the battery. What you see when you look at the outside of a battery is the steel case put around the working parts to help prevent leaks. The case doesn't always do its job, as you will consider later in the lesson. You are not going to be given a set of instructions to follow to make the model. Instead, you will be given a description of what is inside the battery to deduce what you would see ]if you looked at the inside of the battery. This activity is a bit harder than following a set of instructions to put together a model. It's meant to be harder. This is why there are no labels on the parts. You must work out what the parts are, and where they go, using information from the description and other clues such as size and shape. Introduction to electricity Set 3

102 2 Don't be in too much of a hurry to stick the parts together. Make sure first that you have all of the parts in their proper places before you start to glue. When you have all the parts in their proper places, stick your model on the send-in page for this lesson. There are two copies of the page with the cut out parts. This will let you have one copy to practise on, and another copy to put together to send in once you have worked out how to make the model. Read through the whole description below before you start. Description Here is a description of the inside of the battery. In the centre of the battery is a carbon rod about 1 cm wide. On the top of the carbon rod is a metal cap. On each side of the carbon rod is a wide layer of chemicals called the cathode mix. Between the cathode mix and the zinc can is a mixture of different chemicals called the electrolyte paste. A separator sits in the bottom of the zinc can. It is about 5 cm wide and 0.5 cm high. The zinc can doesn't have a lid. Instead of a lid, there is a layer of bitumen on each side of the metal cap to stop the chemicals inside the battery from drying out. The bitumen layer is about 0.5 cm thick and goes across to the sides of the zinc can. The top of the bitumen layer is level with the tops of the sides of the zinc can. Half of the metal cap sticks up above the top of the bitumen layer. Exercise 11.1 Now make your model battery on your send-in page. Label all the parts of your model. Introduction to electricity Set 3

103 3 Cut around the parts of the model battery below. Use them to construct a model that matches the description on page 2. Introduction to electricity Set 3

104 4 Introduction to electricity Set 3

105 5 This is a spare copy of the parts of the model battery. Introduction to electricity Set 3

106 6 Introduction to electricity Set 3

107 7 Is it a battery? So far in this lesson, you have been using the everyday meaning of the word battery. What people usually call a battery has another special name. In science, it is usually called a dry cell. You have probably met the word cell before when you studied living things. In biology, the word cell means the unit of life. That is, all living things are made up of cells. In physics and chemistry, the word cell means a different kind of unit. A cell is a unit or device that produces an electric current as a result of a chemical change. In a cell, chemical energy is changed into electrical energy. Here is an example of a wet cell. globe wire beaker zinc acid copper 1. What are the chemicals in this wet cell? 2. How would you see that chemical energy is changed to electrical energy in this cell? Check your answers. Introduction to electricity Set 3

108 8 Can you imagine carrying a wet cell around with you? Do you think that it would be very portable? Which would you rather carry around in your pocket, a wet cell or a dry cell? It I had a choice, I would take the dry cell. (There is a place where wet cells are carried around in a car. You may have seen someone adding water to a car s battery.) What do scientists mean by battery? In science, the word battery means a number of cells joined together. Think about what is inside a nine volt battery like the one you used in your tester. Inside a nine volt battery The nine volt battery you used in your tester isn t a dry cell. It is really a battery. Have a guess what you would see if you took off its metal cover. Did you say that you would see some cells joined together (because this is what the term battery means)? Below is a sketch of a nine volt battery. The front of its metal cover has been left off so that you can see what is inside. terminal metal cover two of the 1.5 volt cells Introduction to electricity Set 3

109 9 Look at the diagram at the bottom of the previous page. Can you identify the cells inside the battery? Each of the cells is a 1.5 volt dry cell. How many cells can you see in the battery? Did you count six dry cells in the battery? The six 1.5 volt dry cells are joined together to make a 9 volt battery. (6 x 1.5 volts = 9 volts) Why do you need a battery in your tester? The purpose of a battery (or of a cell) is to supply electrical energy to your circuit. Your circuit cannot work without a source of electrical energy. Take care with batteries There are some important reasons why you should take care with batteries. You can protect your own electronic equipment as well as the environment. Protecting your electronic equipment The metal case around a dry cell is designed to stop the chemicals from leaking out but it doesn t always do its job. You may have seen this for yourself if you have ever left a battery or some dry cells in an appliance like a radio or cassette recorder, then put it away and forgotten about it for a long time. What happens when you get the radio out of the cupboard months later? You turn the radio on and find that it doesn t work, so you open it up to check on the battery or dry cells. Yuk! There are rustycoloured marks and puddles inside the battery compartment. The chemical mixture that has leaked out of the dry cells has damaged the radio. To stop this happening, you need to take the batteries out before you put the appliance away. In the future, you may be able to use solid batteries that are less able to leak. Introduction to electricity Set 3

110 10 Protecting the environment Most batteries contain toxic chemicals. When they are thrown away, the mercury and other chemicals in them will eventually be released into the environment. (Never throw batteries in a fire, even when the batteries are worn out. Burning batteries doesn t get rid of the toxic chemicals: it just releases them into the air. There is also a risk of the batteries exploding and injuring someone.) We don t want our water, air, food or ourselves poisoned, so we need to think about the kinds of batteries we use and cut down on the number of batteries we throw away. Kinds of batteries The kind of battery that is often used in torches, toys and portable sound equipment is the alkaline battery. Alkaline batteries such as Energiser and Duracell work better than ordinary (carbon-zinc) batteries in many appliances but alkaline batteries have more mercury in them. Tiny silver button batteries for watches, calculators and hearing aids are much safer for the environment but they are expensive. New kinds of batteries are being investigated by industry (such as fuel cells and aluminium-air batteries), with the hope that more effective and less polluting batteries can be developed for use in many appliances and situations. Reducing our use of batteries One way to reduce the number of batteries that you throw away is to get an adaptor so that you can use main power instead of using batteries, but this isn t always possible or convenient. Another way is to use rechargeable batteries. (Only ever recharge rechargeable batteries. If you put ordinary or alkaline batteries into a charger, they could explode. This would damage the charger, anyone nearby and the environment.) Many rechargeable batteries are NiCads (nickel-cadmium batteries). They cost more to start with, and you need to get a charger, but they can work out cheaper in the long run. NiCads can be recharged up to 500 times so you throw away fewer batteries. But cadmium is toxic so even throwing away rechargeable batteries causes some harm to the environment. NiCads are being replaced by lithium solid-state batteries. These can be used in watches, cameras and laptop computers. Lithium solid-state batteries are rather expensive but they do not cause as much damage to the environment when they are finally thrown away. Exercise 11.2 In Lessons 11 and 12, you have increased your scientific understanding about batteries and thought about using batteries responsibly. In Exercise 11.2, you'll present some of this information and identify ways that batteries are used. Introduction to electricity Set 3

111 11 Lesson 13 Diagrams for circuits Here is a diagram of an electrical circuit. 1.5 V battery wire wire lamp It has to be a rather big diagram for a very simple circuit so that there is room to label all the information and show what the components are like. Scientists (and electronics technicians) needed a simpler way to show the parts of a circuit. They developed a diagram called a circuit diagram. Circuit diagrams are not just pictures of an electrical circuit. People use them as a pattern for making the electrical circuit. To avoid any confusion, there is a set of symbols used to represent components. Similar sets of symbols are used throughout the world. If you pick up a circuit diagram from any country, you should still be able to understand it once you have learned the symbols. Circuit symbols On the next page are some of the symbols used in circuit diagrams, together with the names of the components they stand for. You are expected to: recognise the symbol name the part the symbol represents draw the diagrams from memory. Two of these names have an asterisk, *, next to them, the diode and the LED. You aren't expected to learn to draw these two symbols from memory but you are still expected to be able to copy them, recognise them and name the part the symbol represents (stands for). Introduction to electricity Set 3

112 12 Name Symbol wire closed switch open switch probe or may be curved lamp or globe resistor or battery 1.5 V cell a number of cells capacitor *diode K A *LED K A Spend some time now learning the symbols. Practise on your own paper. Use the same technique that you use to learn spelling. 1. LOOK carefully at the symbol. Identify patterns and features. 2. SAY the name of the symbol while you look at it. 3. COVER the symbol. 4. WRITE, or in this case, DRAW the symbol from memory. 5. CHECK that you have drawn it correctly. Fix any mistakes and try again until you have it right. Introduction to electricity Set 3

113 13 Now that you have learned the symbols, test yourself by covering the second column of the table on page 12 and drawing the symbols down the right hand edge of the page. Then check them carefully. Next, cover page 12 and name each of the symbols shown below. Then uncover page 12 and check your answers. Symbol Name K A K A or Exercise 13.1 There is a test to complete in the send-in pages. Don t be tempted to cheat it is only yourself who loses out. There is not much point in circuit symbols on their own. They need to be combined into a circuit diagram. Introduction to electricity Set 3

114 14 Setting out the circuit diagram Here is a sketch of a circuit. Really, the components in this sketch should be labelled because you do not have a key about what each drawing means. 9 V What are the components in this sketch? Here is a diagram of the same circuit. 9 V What are the components in this diagram? You can see that both the sketch and the circuit diagram show the same parts: 9 V battery wires 2 lamps or globes. Introduction to electricity Set 3

115 15 Perhaps you expected the symbols to be put in the same place as the components in the sketch, like this. 9 V Scientists don't draw circuit diagrams this way because it has been agreed that straight lines will be used as symbols for wires. The same circuit diagram could be drawn like this: 9 V or this: 9 V They all say the same thing. Introduction to electricity Set 3

116 16 Identifying symbols in circuit diagrams In this activity, you are going to: identify symbols name components record the names in a table. The first three symbols have been named for you, to give you a chance to check that you understand the instructions. The diagrams are printed on this page. The table for your answers is on the next page. 1 5 K 6 A 9 V K 9 A V 10 K A 16 K A Introduction to electricity Set 3

117 17 Part number Name of circuit component 1 9 volt battery 2 resistor 3 closed switch Check your answers in the answer pages. Now that you have checked that you can identify circuit symbols when they are used in circuit diagrams, it is time to look at how electric current travels around an electrical circuit. Introduction to electricity Set 3

118 18 Interpreting circuit diagrams 1. Look at the circuit diagram below V 3 2 (a) Which component in this circuit supplies electrical energy? (b) Energy is carried around the circuit by moving electrical charges. That is, energy is carried around by the electric current. Start at 1 and trace around the pathway of the circuit until you return to the battery at 4. This shows how the current moves through the circuit. (c) Energy is transferred from the battery to other components by the electric current. What happens to the electrical energy as it is carried through the circuit by the electrons? (d) Join the probes on your tester again. What energy transformation can you see? Globes (and LEDs) are not the only components of circuits that are able to transform electrical energy. Your LED gives out light, but what form of energy does the resistor give out? Put you hand on the resistor in your tester while it is working. Can you feel any heat? These questions reviewed information you learned in Set 1. Check your answers to see if you need to revise Lesson 4. Introduction to electricity Set 3

119 19 2. Study this circuit diagram. (a) Trace the path of the electric current around the circuit. (b) List the components in the order that the current passes through them. (c) Where is energy from the cell transferred to in this circuit? 3. Here is another circuit. 4.5 V (a) Will current flow through this electrical circuit? Why or why not? (b) If the switch is closed, which components will transform energy from the battery? 4. Look carefully at this circuit. 9 V Will current flow through this electrical circuit? Why or why not? Check all of your answers now. Introduction to electricity Set 3

120 20 Drawing circuit diagrams Can you draw circuit diagrams by yourself? Study this simple circuit. lamp 1.5 V wire cell closed switch direction of current flow Now draw a circuit diagram for the circuit. The dotted box below is provides as an outline. Compare your diagram with the one in the answer pages. What could have a circuit diagram drawn for it? Look around your room. Can you see five things near you that could be represented by a circuit diagram? List them. There are some suggestions in the answer pages. Exercise 13.2 Now you are ready to draw a circuit diagram for your tester and interpret it. Please complete this send-in exercise now. Introduction to electricity Set 3

121 21 Lesson 14 Predicting You will need to do this lesson over two days so I have divided it into two parts, one for each day. Part 1: Making predictions When you make a prediction, you say what you expect to happen in the future. Have you ever made a prediction? I m sure you have. (You ve already made some in this unit!) Bet it will rain tomorrow! My mother will kill me! This horse is a sure thing to win the Melbourne Cup. Balmain will beat Parra at footy on Saturday. All of these can be predictions. A prediction is not just a guess. When you make a guess, you don t have any information to help you choose your answer. But predictions are based on information. Let s look at an example. At breakfast time, Sarah s father said, 'Guess who I m going to see today.' Sarah has no idea who her father is going to see because he hasn t mentioned anything about his plans. As she has no information to help her choose an answer, she can t make a prediction, only a guess. The difference between a prediction and a guess is that you expect your prediction to happen but you know that your guess is just a 'stab in the dark'. Introduction to electricity Set 3

122 22 Here is another example. A friend holds a coin and asks, 'Heads or tails?' You say, 'Heads!' Is this a guess or a prediction? Why? It is a guess because you have no information to help you know which side of the coin will land upwards. (If you knew that your friend had a double-headed coin then you could make a prediction!) Try one more example. Belinda took her mother s good white jumper when she went to camp. Now it is torn. Belinda knows that she isn t allowed to wear her mother s clothes without permission. Belinda said, 'My mother will kill me!' Is Belinda making a guess or a prediction? Why? Belinda is making a prediction. (She doesn t mean that her mother will really kill her.) She is predicting that she will be in big trouble. This is a prediction, not a guess, because it is based on information. She has reason to expect that she will be in trouble because she has disobeyed her mother and damaged a jumper. Your turn to make a prediction One of the best known areas that people make predictions about is the weather. You are going to predict tomorrow s weather. I want you to: make predictions about three aspects of the weather record these predictions and write down the information each prediction is based on. I ve given you space on the next page to record your predictions and the information each prediction is based on. You don t have to write down your predictions. Just choose one of the words from each group and draw a circle around it. You have a few lines under each prediction to write down the information that your prediction is based on. Introduction to electricity Set 3

123 23 Tomorrow will be: 1. cold cool warm hot because 2. clear cloudy because 3. dry showery rainy because When you made your prediction, you probably thought about the season and the weather pattern over the last few days. It if has been snowing for the last week, you wouldn t expect tomorrow to be hot. Or, if you are in the middle of a heatwave, you wouldn t expect tomorrow to be cold. If you haven t been able to find any pattern in the weather in your area, you wouldn t be able to make a prediction. This is because a prediction is based on the assumption that the same pattern will continue. So when there is no pattern, you could make a guess but you wouldn t feel confident that your guess would be right. In the next part of this lesson, you are going to test the predictions you made today. Because your predictions are about tomorrow s weather, you need to wait until tomorrow to do Part 2. Introduction to electricity Set 3

124 24 Part 2: Testing predictions When you want to make a prediction about something, you don t just make a guess off the top of your head. The first thing you do is to sort through the ideas you have about the topic. You also look at what you know about the topic, to see if you can find any patterns to use as a basis for your prediction. Now that you have some predictions, what do you do with them? The next step is to test the predictions. Testing your predictions Look at the predictions you made and recorded yesterday. You predicted that the weather would be, and. How could you test these predictions? This is an easy example because you don t have to design a special experiment to be able to test your predictions. All you need to do is to observe the weather! Your observations Choose words for predictions from the same words used to record your observations. To do this, circle one word from each group. Choosing from the same words to record both your predictions and observations should make it easier for you to compare them. Today is: 1. cold cool warm hot 2. clear cloudy 3. dry showery rainy. It is easier to compare predictions and observations if you can look of them at the same time. One way to do this is to put them into a table. Introduction to electricity Set 3

125 25 Presenting predictions and observations You want to compare two things: the predictions and the observations. This is why I chose to have two columns in the table. You could write predictions in one column and observations in the other. Predictions Observations The table could have been drawn across the page instead of down the page. Here is the same table drawn across the page. Predictions Observations You can choose which table you want to use: the one running down the page or the one running across the page. Fill in your predictions and observations in the table you choose. Comparing observations and predictions Now that you have your predictions and your observations arranged in a convenient form, you are ready to compare them. Did your predictions agree with your observations? If your predictions did not agree with your observations, what should you do? Of course you don t change your predictions or your observations! What you need to do is to change the ideas you based your predictions on so that you can make better predictions next time. Introduction to electricity Set 3

126 26 Perhaps you predicted that the morning would be hot because it is summer and because the last two mornings were hot but then observed that this morning was cool. Even though what you predicted didn t happen, you have learned something from the activity. You have learned that you need to collect more information to use if you want to predict the weather. The same is often true of the experts, the meteorologists. If your prediction did happen, you mustn t get too excited! Before you can be sure that your ideas are right, you have to make and test a number of predictions. This is the only way to check that your first result wasn t a coincidence. Don t waste your time In the next lesson, you will make and test some more predictions. Don t be tempted to work backwards. Sometimes students think that they can save a bit of time or get more marks if they make their observations first, then go back and write their predictions. This does make sure that their observations always agree with their predictions but that isn t the purpose of the activity. These students have missed the point and have wasted their time. Your teacher won t be giving marks for making predictions. S/he will be looking at how you test the predictions and at what you learn from the activity. Introduction to electricity Set 3

127 27 Lesson 15 Investigating In this lesson, you are going to make some predictions about materials then use your tester to investigate them. You'll be able to compare your predictions and observations at the end of your investigation. So that you can be confident about making your own predictions and performing your own investigation, here is an example that is similar to the activity you will do. Jane and Jenny investigate Scientists Jane and Jenny are selecting materials for use in their new rocket program. They need to find materials they could use instead of copper and rubber. Copper is called a conductor because electric current passes through it easily. Most conductors are metals, like copper. Any material to replace copper must be a conductor. Electric current does not pass through rubber so rubber is called an insulator. All insulators are made from substances that are not metals. Any material they choose instead of rubber must be an insulator. After some research, Jane and Jenny chose ten materials to test: five they expected to be conductors and five they expected to be insulators. They wrote the names of all ten materials in the 'Name' column of a table. This has been copied onto the next page. Introduction to electricity Set 3

128 28 Name Prediction LED lit up Meaning sodium germanium plutonium iodine boron rubidium phosphorus tellurium lithium potassium Did you notice that the heading of the second column is 'Prediction'? In this column, they wrote conductor next to the materials they expected an electric current to pass through. In the same column, they wrote insulator next to materials they didn t expect a current to pass through. Here is a copy of the table with Jane and Jenny's predictions. Name Prediction LED lit up Meaning sodium germanium plutonium iodine boron rubidium phosphorus tellurium lithium potassium conductor conductor insulator insulator conductor conductor insulator insulator conductor insulator Introduction to electricity Set 3

129 29 Jane and Jenny made an electronic tester like yours and used it to test each material. They touched the material with the metal part of the alligator clips, making sure that the clips did not touch each other. If the LED lit up, they wrote yes in the 'LED lit up' column. If the LED didn t light up, they wrote no in the 'LED lit up' column. Name Prediction LED lit up Meaning sodium conductor yes germanium conductor no plutonium insulator yes iodine insulator no boron conductor no rubidium conductor yes phosphorus insulator no tellurium insulator no lithium conductor yes potassium insulator yes Jane and Jenny know that the LED lights up when a current flows through the tester circuit. This happens only if the material is a conductor. Every yes in the 'LED lit up' column means that the material is a conductor. Every no means that the material is an insulator. Jane and Jenny used this information to help them fill in the 'Meaning' column. Complete the table above to interpret Jane and Jenny's observations. If you have any doubts, there is a completed table in the answer pages. Which of their predictions were not supported by their observations? You can check this answer from the answer pages too. Introduction to electricity Set 3

130 30 Your investigation Do you remember what conductors and insulators are? Materials that an electric current passes through are called conductors and materials that a current doesn t pass through are insulators. You are going to use these definitions and the processes that Jane and Jenny used in their investigation. Like them, you are going to make and test predictions about materials. You won t be able to use any of the same materials as they did. Jane and Jenny chose their materials from their laboratory. You are going to choose your materials from around your place. Investigating with your tester You are going to choose ten materials from around your place: five you expect to be conductors and five you expect to be insulators. Like Jane and Jenny, you want to find out if your chosen materials are conductors or insulators. Although you are not working on a rocket project, you will use the same processes of: making predictions making observations and comparing your predictions and observations. Getting ready Choose ten materials from around your place: five you expect to be conductors and five you expect to be insulators. I don t expect you'll be confused about the meaning of the word material. From what you read in Jane and Jenny's investigation, I m sure that you realise that I don t mean material used for sewing. Some things are made of more than one material so you have to be sure that you are testing one material at a time. For example, one of my saucepans is made out of two materials: black plastic in the handle and aluminium in the pot. Introduction to electricity Set 3

131 31 If you want to test the black plastic, you have to make sure that you put the two probes on the black plastic. You can t test the saucepan by putting one probe on the plastic and one on the aluminium because this would not be testing one material only. probes black plastic handle aluminium pot Write the name of each of the ten materials you are going to test in the 'Name' column in the table in Exercise 15.1 in the send-in pages. In the 'Prediction' column, record whether you think that the material is a conductor or an insulator. (Remember, conductors are usually made from metal but insulators are not.) And remember that there is no need to 'fudge' your answers. The 'Prediction' column won t be marked. I m giving you a chance to practice making and testing predictions. Your teacher will be marking only the 'Meaning' column and your discussion of the activity. Finishing your investigation Take some time now to go back and read page 29 again, then finish your investigation. (If any of your observations do not support your predictions, this will give you a chance to change your ideas [but not your send-in page] about which materials are conductors and which are insulators.) Exercise 15.1 Make sure that you have completed all of this send-in exercise about your investigation. Introduction to electricity Set 3

132 32 Pulling ideas together At the beginning of this unit, you learned about static electricity. The idea of conductors and insulators that you have used in this lesson is also very important for static electricity. Go back to Lessons 2 and 3 and see what kinds of materials could become electrostatically charged. 1. Name the materials that became electrostatically charged. 2. Would you predict that these materials are conductors or insulators? Why? Check your answers before you continue. Exercise 15.2 This send-in exercise lets you show your teacher that you can pull together ideas from throughout Sets 1 to 3. Please complete Exercise 15.2 now. Introduction to electricity Set 3

133 33 Suggested answers Lessons 11 and 12 Page 7 Energy for a circuit Is it a battery? 1. The chemicals in the wet cell are zinc, acid and copper. 2. You would observe that the light globe shines when energy has been transformed from chemical energy in the battery to electrical energy in the circuit. (For the globe to shine, electrical energy is transformed into light energy at the globe.) Lesson 13 Page 17 Diagrams for circuits Identifying symbols in circuit diagrams Here is the completed table. If you get any answers wrong, go back and do page 12 again. Part number Name of circuit component 1 9 volt battery 2 resistor 3 closed switch 4 resistor 5 resistor 6 diode 7 wire 8 cell 9 LED 10 capacitor 11 open switch 12 battery 13 open switch 14 resistor 15 lamp (or globe) 16 diode Introduction to electricity Set 3

134 34 Lesson 13 continued Interpreting circuit diagrams Page (a) The 9 V battery supplies electrical energy. (c) Electrical energy is transformed into light energy at the globes. Page (a) The electric current goes from the side of the cell symbol with the thin line around the circuit and back to the side of the cell symbol with the thick line. (b) The components, in the order that current passes through them are: wire, diode, wire, resistor, wire. (You do not have to list the wires.) (c) Energy from the cell is carried around the circuit so you can guess that it is transformed into another form of energy by either the diode or the resistor. It is the resistor! The resistor transforms electrical energy into heat. direction of current 3. (a) Electric current will not flow through the circuit because the switch is open. (b) Electrical energy will be carried around the entire circuit. But at the globe, it will be transformed into light and at the resistor, it will be transformed into heat. 4. Electric current will not flow through this circuit because the diode is backwards in the circuit. (If you go around the circuit starting from the thin line in the battery symbol, the arrow part of the diode symbol should be pointing in the same direction that you are going.) Page 20 Drawing circuit diagrams Here is the completed diagram. 1.5 V What could have a circuit diagram drawn for it? Anything that uses dynamic (moving) electricity must have an electrical circuit and so you could draw a circuit diagram for it. That is, a circuit diagram could be drawn for any appliance that plugs into a powerpoint, works with an electrical switch or has batteries. Introduction to electricity Set 3

135 35 Lesson 15 Page 29 Investigating Jane and Jenny investigate Here is the completed table. Name Prediction LED lit up Meaning sodium conductor yes conductor germanium conductor no insulator plutonium insulator yes conductor iodine insulator no insulator boron conductor no insulator rubidium conductor yes conductor phosphorus insulator no insulator tellurium insulator no insulator lithium conductor yes conductor potassium insulator yes conductor Jane and Jenny s predictions and observations do not match for germanium, plutonium, boron and potassium. Page 32 Pulling ideas together 1. In Set 1, you learned about or actually electrostatically charged plastic (such as spoons, rulers, combs and balloons), fabric (such as wool, silk and synthetics) and ebonite wood. 2. Did you predict that these materials are all insulators? From your investigation in Lesson 15, you probably found that conductors were made of metals but other materials (ones that are not metals) were insulators. All the materials you electrostatically charged in Set 1 are not metals so they are probably insulators. Introduction to electricity Set 3

136 36 Introduction to electricity Set 3

137 37 Send-in page Name Lessons 11 and 12: Energy for a circuit Exercise 11.1 Use the information and cut-out parts from the lesson to make a model of a 1.5 V battery. Remember to label all the parts of your model. Introduction to electricity Set 3

138 38 Exercise To a scientist, what is a battery or cell? (Hint: Why do you need to put a battery into a circuit? What does a battery do?) 2. What happens inside a battery or cell can be explained using the science of chemistry. Scientists are developing new and better batteries and cells to make them more useful and safer. (a) Batteries and cells have many uses in our society. Make a list of the appliances in your home that use batteries or cells. Instead of just writing down all the appliances you know about, ask the rest of your household if they know of any other appliances at your place that use batteries. The appliances in my home that use batteries are (b) Look at the list of uses of batteries that you have made. How important do you think batteries are for our technological society? Explain. (c) Suggest some ways that you could cut down on the number of batteries you or your household use. Introduction to electricity Set 3

139 39 Send-in page Name Lesson 13: Diagrams for circuits Exercise 13.1 Complete the table below. Name Symbol battery closed switch K A Introduction to electricity Set 3

140 40 lamp K A resistor probe Introduction to electricity Set 3

141 41 Send-in page Name Lesson 13: Diagrams for circuits (continued) Exercise 13.2 Drawing a circuit diagram for your tester Now that you can identify and draw the symbols for components, you are going to draw the circuit diagram for your tester. Plan your circuit diagram below. Boxes have been drawn in the spaces between the dot numbers. In each box, write the name of the component you put in this place when you built your tester In the diagram on the next page, draw in the symbols for these components. This will change the layout diagram above into a circuit diagram. Think about the way to draw the symbols for the battery and diodes so that the electric current can flow around the circuit. (The K end of the protection diode is near dot seven. The K end of the LED is near dot three. The thin line of the battery symbol is closest to the A end of the diodes.) Introduction to electricity Set 3

142 42 Exercise 13.2 (continued) Now draw a circuit diagram for your tester (without dots and numbers) in the space below. Where does energy come from in your tester? Where does it go to? How does energy move from one place to another? Write a paragraph about your tester to answer these questions. Introduction to electricity Set 3

143 43 Send-in page Name Lesson 15: Investigating Exercise Complete the table below about your investigation. Name Prediction LED lit up Meaning 2. Do any of your observations not match your predictions? If so, which ones? 3. List the insulators from your investigation. Introduction to electricity Set 3

144 44 Exercise 15.2 This unit has been about the scientific concept of electricity. 1. Write a scientific definition of electricity. (Look back at Lesson 1 in Set 1 if you need to review your ideas.) 2. Why are components in an electrical circuit connecting with materials that are conductors (such as wire) rather than with insulators? 3. Why can insulators, not conductors, become electrostatically charged? Introduction to electricity Set 3

145 We need your input! Can you please complete this short evaluation to provide us with information about this unit. This information will help us to improve the design of these materials for future publications. 1 Did you find the information in the unit clear and easy to understand? 2 What sort of learning activity did you enjoy the most? Why? 3 Name any sections you feel need better explanation (if any). 4 Were you able to complete each part in around five hours? If not which parts took you a longer or shorter time? 5 Do you have access to the appropriate resources? This could include a computer, graphics calculator, the Internet, equipment and people to provide information and assist with the learning. Introduction to electricity Evaluation