DC Electricity Discovery and Developments

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VEA Bringing Learning to Life Program Support Notes Grades 8 10 DC Electricity Discovery and Developments 24mins Teacher Notes by John Nicholson, B Sc (Hons), Dip Ed, Ph D, Grad Dip Comp Ed, M Ed

1 VEA Bringing Learning to Life Program Support Notes Grades 8 10 DC Electricity Discovery and Developments 24mins Teacher Notes by John Nicholson, B Sc (Hons), Dip Ed, Ph D, Grad Dip Comp Ed, M Ed Produced by VEA Pty Ltd Commissioning Editor Christine Henderson B.Sc. Ph.D. Dip.Ed. Executive Producer Mark McAuliffe Dip.Art (Film & TV) Dip.Ed. B.Ed. Ph.D. Video Education America To order or inquire please contact VEA: America Phone: Facsimile: vea@veavideo.com Website WARNING This program is protected by copyright laws worldwide. Unauthorized copying, in whole or part, in any format, can result in substantial penalties for both individuals and institutions These notes can be freely copied for classroom use only.

2 For Teachers: Introduction This video attempts to look at the origins of electricity through the first uses of static electricity by the Greeks and then to the use of static electricity by Gilbert and other popular displays by scientists in the 18 th and 19 th centuries. The work of Galvani and Volta started the study of current electricity with the discovery of the chemical battery and the concept of a complete circuit and the flow of positive charges as a one way or direct current. The study of battery powered electricity was driven by commercial applications such as electrolysis and electroplating. The program looks at the processes involved in both these applications. The discovery of the electron by Thomson in 1897 threw a spanner in the works when it was discovered that the moving charges in metal wires was actually the negatively charged electron. The program looks at the concept of potential difference and EMF and looks at gravitational and water models for current flow. Resistance to flow is introduced and then the use of both ammeters and voltmeters to monitor flow and potential is shown. The concept of series and parallel circuits is introduced. Ohm s law is introduced showing the interaction of voltage, current and resistance. Energy is lost when resistance is present. DVD Timeline 00:00:00 Introduction 00:00:52 First discoveries 00:04:22 Summary 00:04:44 New tricks 00:07:20 Summary 00:07:46 Leap of faith 00:12:46 Summary 00:13:43 Why charges move 00:17:53 Summary 00:18:27 Simple circuits 00:21:44 Summary 00:22:34 Conclusion 00:23:34 Credits 00:24:14 Program end

3 Student Worksheet: Before Viewing the Program 1. Get hold of a hose and show the different levels of pressure giving different flow rates. Perhaps measure the rate of flow by measuring the volume of water delivered for fixed amounts of time. Relate this to electric current. Show that kinks in the hose can slow the rate of flow (current) and relate this to resistance in an electrical circuit. 2. Use an INTERNET search to look for experiments by Galvani, Volta, Gilbert and Victorian static electricity parlor tricks. 3. Try setting up a daisy chain of students and pass a static charge from one end to the other either by scuffing feet on carpet or use a Van De Graff generator. 4. Use plastic rulers and woolen jumpers to try some simple static electricity activities such as picking up confetti. NOTE: static electricity experiments work best on hot dry days.

4 While Viewing the Program 1. How do objects become charged by static electricity? 2. Which charge actually moves, the positive charge or the negative charge? 3. Why is the boy in parlor trick suspended by silken ropes? 4. Why is the charging of objects by rubbing called static electricity since charges do move? 5. What unfortunate creature was sacrificed for science by Galvani? 6. How did Volta bring forward the understanding of electricity? 7. The program talks about a Leap of Faith. What is meant by this statement? 8. How did the commercial use of electric current in electrolysis and electroplating help the study of electricity?

5 9. In the production of aluminum by electrolysis carbon dioxide is formed at the positive carbon anode. The negative oxygen ions react with the carbon at the anode to form carbon dioxide. What happens to the negative charge on the oxygen ions and why is this important in the concept of an electric circuit? 10. Why do we still talk about conventional positive current and not the flow of negative electrons? 11. What does an Electromotive Force (EMF) do? 12. Charges flow from points of potential energy to points of potential energy. 13. A point M in a circuit has a potential of 8 volts and another point N is at 3 volts. What is the potential difference between these two points M and N? 14. Which way does the conventional current flow? From M to N or from N to M? 15. Which way would the electrons flow if the points M and N were connected by a metal wire? 16. A current of 3 amperes flows from a point in a circuit at a potential of 8 volts to another point in the circuit at a potential of 2 volts. What is the resistance between these two points?

6 17. Voltmeters are placed across (in parallel) or in line (series) in a circuit? 18. Voltmeters have very high resistance. Why? 19. Ammeters are placed across (in parallel) or in line (series) in a circuit? 20. Ammeters have very low resistance. Why? 21. The flow of charge leaving a battery is higher, lower or the same as the flow of charge coming back into a battery? 22. What is actually lost by the charges in a circuit when current flows around the circuit? 23. Why is the concept of a completed or closed circuit important? 24. Explain what happens to the current in a series circuit as opposed to a parallel circuit.

7 25. When using water to model current flow in a circuit what is the electrical equivalent of: a) The hose b) The reservoir c) The tap d) A kink in the hose e) The flow of water

8 After Viewing the Program 1. Set up a simple circuit using a battery, switch and a light globe to demonstrate a series circuit. switch battery globe 2. If available measure the voltage drop across the globe and the current through the globe with a voltmeter and an ammeter. switch battery globe V 3. Place a second light globe in: a) series then b) parallel with the first globe. Repeat your current and voltage measurements. A

9 Other Relevant Programs Available from VEA Energy Rules! - The Conservation of Energy and Momentum Bohrs Model of the Atom Corrosion Chemistry Cellular Signaling Please visit our website for many more relevant programs VEA Bringing Learning to Life

INVESTIGATION ONE: WHAT DOES A VOLTMETER DO? How Are Values of Circuit Variables Measured?

INVESTIGATION ONE: WHAT DOES A VOLTMETER DO? How Are Values of Circuit Variables Measured? How Are Values of Circuit Variables Measured? INTRODUCTION People who use electric circuits for practical purposes often need to measure quantitative values of electric pressure difference and flow rate