Electricity Simulation: Sound

Transcription

1 Electricity Simulation: Sound Activity One Introduction How do telephones and radios send sound so that we hear it? When anything vibrates, it produces sound. When sounds enter a microphone, the sound waves cause a thin diaphragm in the microphone to vibrate. The vibrations are converted into electrical signals that are then sent out as radio waves. These waves are then received by an electronic device that amplifies and changes the signals back into sound waves. Heinrich Hertz, a German physicist, was the first to show that it was possible to send electrical energy through the air. In the mid 1890s, Guglielmo Marconi, an Italian inventor and scientist, developed a way to send telegraph signals without wires. Now, thin glass threads called fiber optics to carry digital messages. The technology has changed, but the physics is similar. Sound waves are transformed into electrical energy and sent out as radio or light waves. When received, the waves are transferred back into sound waves by tiny electromagnets. Directions Use the Electricity simulation to learn more about electricity. After exploring how the size of a magnet affects the current in a circuit, consider how the strength of a generator might relate to the sound heard from a speaker. Procedures 1. Click on the Start Here button and read the text. If you need more information, click and read the Background. Close the window when you are done. 2. From the pull down menu under Strength of Magnet, select Small. Under Number of Turns of Coil in Wire, select Many. Under Speed to Crank Generator, select Fast. These choices create an electricity generator. 3. The variables that test the current are Wattage of Light Bulb and How to Wire the Light Bulb. Start with 1 Bulb, and a light bulb that is 35 watts. Click on the Start Generator button. 4. Observe how the coils turn, the reading on the ammeter, and the light bulb. Estimate and record the ammeter reading below. 5. Repeat this with one 60-watt bulb then the 100-watt bulb. Estimate and record the reading on the ammeter.

2 Light bulb Generator 35 watt 60 watt 100 watt Small/many/fast Large/few/fast Large/many/fast 6. Now change the generator. Under Strength of Magnet, select Large. Under Number of Turns of Coil in Wire, select Few. Under Speed to Crank Generator, select Fast. Select 1 Bulb and 35 watts. 7. Click on the Start Generator button. How was this generator different than the first? 8. Estimate and record the reading on the ammeter. 9. Repeat the steps above for a 60-watt and 100-watt bulb with the same generator. 10. Again change the generator. Under Strength of Magnet, select Large. Under Number of Turns of Coil in Wire, select Many. Under Speed to Crank Generator, select Fast. Test the three bulbs as before, staying with the one-bulb choice. 11. A typical portable CD player requires about 5 volts of electricity to operate. Which generator do you think would be large enough to power a portable CD player? Why?

3 Electricity Simulation: Sound Activity Two Introduction The vibration of air is sound when it hits an object that can vibrate. Electricity allows sound from one place to be carried over a long distance. Electrical devices transform sound waves into electrical impulses. These impulses are then either stored or sent out in radio waves. Telephones transmit sound as electrical signals. There are three basic components of sound reproduction: the microphone, speaker, and amplifier. A microphone changes sound waves into electric signals. The speaker changes those electric signals produced by a microphone back into sound. An amplifier strengthens the electric signals to increase the volume. You hear words or music after the speaker has carried the amplified sound waves to your ear. Every CD or tape player, radio, public address system, television, and sound system must have an amplifier and speaker. Think of the eardrum. It is a thin tissue that vibrates when sound waves enter the ear. The microphone, speaker, and amplifier all use a thin material called a diaphragm that vibrates when hit by sound waves or an electrical signal. The diaphragm is usually cone-shaped and is attached to a coil of wire suspended in a magnetic field produced by a permanent magnet. A signal current in the suspended coil, called a voice coil, creates a magnetic field that interacts with the alreadyexisting field. This causes the coil and the diaphragm attached to it to vibrate. Directions Use the Electricity simulation to learn more about the relationship between electricity and magnetism. Apply what you learn to the concept of sound transmission. Procedures 1. Click on the Start Here button and read the text. If you need more information, click and read the Background. Close the window when you are done. 2. First, set up a circuit. From the pull down menu under How to Wire the Light Bulb, select 1 Bulb. Under Wattage of Light Bulb, select 100 watt. 3. Now set up your generator. Under Strength of Magnet, select Small. Under Number of Turns of Coil in Wire, select Many. Under Speed to Crank Generator, select Fast.

4 4. Click on the Start Generator button. 5. Estimate and record the ammeter reading below. Generator Small/many/fast Large/few/fast Large/more/medium Large/more/fast Large/many/medium Large/many/fast Ammeter Readings Watts on circuit 100 watt 180 watt 300 watt 6. Change the generator. Under Strength of Magnet, select Large. Under Number of Turns of Coil in Wire, select Few. Under Speed to Crank Generator, select Fast. Leave the circuit with one 100-watt bulb. 7. Repeat steps 4 and Continue testing generators as indicated in the table. What combinations seem best for lighting the 100-watt bulb? Are any about the same? 9. Now change the circuit to see what happens with more watts on the circuit. Under Strength of Magnet, select Large. Under How to Wire the Light Bulb, select 3 Bulbs in Parallel. Under Light Bulb, select 60 watt. 10. Repeat the previous steps to test the different strength generators with this circuit. Estimate and record the ammeter reading for each. 11. Finally, change the circuit from three 60-watt bulbs to three 100-watt bulbs. Keep it as a parallel circuit. Repeat the previous steps to test the different strength generators. 12. What can you conclude about the strength of a generator needed to produce enough volts to light 300 watts?

5 13. An amplifier that would be plugged into an electric guitar needs 120 volts. Which of the generators do you think could produce that much electricity? Why? 14. If you do not think that you can get enough electricity from one of these generators, how could you adapt the system to get the electricity needed for an amplifier?

6 Electricity Simulation: States of Matter Activity One Introduction Since the early 1800s, scientists and inventors have searched for efficient and practical ways to make light bulbs. Arc lamps were the first in 1801, using carbon vapor. Incandescent light bulbs were invented in All light bulbs use gas. Mercury vapor lights were first invented in 1901 by Peter Cooper Hewitt. They work by passing an electric current through a glass tube that contains a tiny amounts of gas. The electrical current excites the gas, causing it to give off a blue-green light. Incandescent bulbs use gas to cool the filament. Mercury gets its name from the Greek word that means liquid silver. It's an element that is rarely found in its free form and is usually extracted from the mineral cinnabar. It is the only metal that is in a liquid state at room temperature, and it is also the heaviest known liquid. As a liquid, it is used in thermometers. Mercury conducts electricity, but not heat. The amount of light produced by mercury vapor is intense, but does not use much electricity. Mercury vapor was therefore used in high intensity security lights in parking areas and street lights. Unfortunately mercury is also highly toxic and dangerous. In the 1950s, high intensity security lights were also made with sodium vapor. These lights are much more efficient than mercury vapor lamps. They make a harsh yellow light, which is not pleasing to the human eye. Research has continued with other gases, and now iodine vapor is used for many high intensity security lights. Directions Use the Electricity simulation to explore the flow of electricity through a circuit with light bulbs of different watts. Apply the results to predict how the generator and circuit could support high intensity lights. Procedures 1. Click on the Start Here button and read the text. If you need more information, click and read the Background. Close the window when you are done. 2. From the pull down menu under Strength of Magnet, select Small. Under Number of Turns of Coil in Wire, select Many. Under Speed to Crank Generator, select Fast. These choices create a generator. 3. The variables that test the current are How to Wire the Light Bulb and Wattage of Light Bulb. You have three choices under each, giving you nine tests on the generator created above. Start with 1 bulb, and a light bulb that is 100 watts. Click on the Start Generator button.

7 4. Look closely at the ammeter. There are marks that indicate relative current from 0 to 10. Record your estimate of the reading in the table below. Ammeter Reading Generator 100-watt bulb Three 60- watt bulbs Three 100- watt bulbs Small/many/fast Large/more/fast La rg e/m a ny/m ed i u m Large/many/fast 5. Repeat steps 3-5 with three 60-watt bulbs in a series. Record the ammeter reading in the table above. 6. Continue testing three 100-watt bulbs in a series. Again record the ammeter reading in the table above. 7. Change the generator as indicated in the table and continue testing bulbs. Record your results above. 8. A mercury vapor light that uses 100 watts of electricity produces the same amount of light as three 100 watt incandescent bulbs. A typical parking lot light uses 400 watts. About how many 100 watt incandescent bulbs would that equal? Which circuit above could support one parking lot light?

8 Electricity Simulation: States of Matter Activity Two Introduction Have you ever looked at a display of light bulbs in a store and wondered about the differences? Many of the differences are because of the gas used in the bulb. The result of different gases is noticeable in the brightness of the light, its color, the cost of electricity, and how long the bulb lasts. Noble or inert gases, are used in many light bulbs because they are good insulators. They do not conduct heat and are non-flammable. These gases have no extra electrons to share, making them very stable. The noble gases are helium, neon, argon, krypton, xenon, and radon. Incandescent bulbs are the most commonly used light bulbs. Electricity heats a filament to an extreme temperature. The light that we see is from that glowing filament. The hotter the filament, the brighter the light. A gas mixture inside the glass bulb slows the rate at which the filament burns, but without lowering the temperature. Regular incandescent bulbs are filled with a mixture of argon and nitrogen. Directions Use the Electricity simulation to explore the relationship between current and watts used in light bulbs. Project how energy can be saved by using lower watt bulbs. Procedures Part 1 1. Click on the Start Here button and read the text. If you need more information, click and read the Background. Close the window when you are done. 2. From the pull down menu under Strength of magnet, select Small. Under Number of Turns of Coil in Wire, select a Few. Under Speed to crank generator, select Slow. These choices create the generator. 3. The variables that test the current are Wattage of Light Bulb and How to Wire the Light Bulb. Select 1 bulb that is 35 watts. Click on the Start Generator button. 4. Look closely at the ammeter. There are marks that indicate relative current from 0 to 10. Record your estimate of the reading in the table below. 5. Repeat this with one 60-watt bulb, and continue with a test of one 100-watt bulb. Record the ammeter reading for each.

9 Ammeter Reading Generator 35 watt 60 watt 100 watt Small/Few/Slow Small/Few/Fast Small/Most/Slow Small/Most/Fast Large/Some/Slow Large/Some/Fast 6. Now, change the generator. From the pull down menu under Strength of Magnet, select Small. Under Number of Turns of Coil in Wire, select Few. Under Speed to Crank Generator, select Fast. This will increase the potential of the generator. Test the bulbs as indicated in the table, recording the results. 7. What patterns do you see in the ammeter readings? 8. What can you conclude about the generator potential as compared to the watts needed by each bulb? Part 2 Halogen light bulbs use the same technology to produce light as regular incandescent bulbs. The halogens are nonmetals in column VII of the periodic table: fluorine, chlorine, bromine, iodine, and astatine. They are very reactive, with seven electrons. This means that they are almost always found in compounds. They are special in that they can exist as a solid, liquid or gas at room temperature. When a halogen mixture is put in a light bulb, it allow the filament to burn hotter and brighter without melting as fast as in an bulb with argon and nitrogen. Fluorescent and neon lights are very similar to each other, with tubes that are filled with a noble gas. They transform electricity into light through a chemical reaction. At each end of the tube is a metal electrode. The electrical current causes the gas to become charged and give off light. Each of the noble gases gives off a different color. The chemical reaction in the neon light results in the neon gas taking on the fourth state of matter-plasma. Neon lights are used in advertising as the length of the bulb necessary for this change of state also allows for curved designs in the glass tubing. Halogen and compact fluorescent bulbs are considered more energy efficient than standard incandescent bulbs. This is because they are able to produce the same amount of light

10 (lumens) with fewer watts. They also last longer because they don't get as hot. The chart below gives the comparison, using lumens as the measure of light, and life in hours to show how long a bulb can last under normal use. Bulb type Lumens per watt Life in Hours Standard Incandescent Halogen Fluorescent Estimate the number watts needed in a halogen and compact fluorescent to equal the lumens from the bulbs tested earlier. Bulb type Wattage of Bulb Standard incandescent Halogen Fluorescent 10. Look back at your data in Part 1 on the previous page. Not all the generators created were able to get maximum lumens from the bulbs. Estimate the watts needed in a halogen and compact fluorescent that will equal the watts in the incandescent bulbs used in the simulation. Then estimate the ammeter reading for each of the generators used in Part 1 of the halogen and compact fluorescent equivalents for the bulbs tested. Generator Small/few/slow Small/few/fast Small/most/slow Small/most/fast Large/some/slow Large/some/fast Ammeter Reading Ha ogen Equivalent Compact Fluorescent Equivalent 35 watt 60 watt 100 watt 30 watt 60 watt 100 watt 11. Why do you suppose that many people do not choose to use these lower watt light bulbs?