course Phy 202
Your work on this experiment is very good.
Experiment 17Capacitors and Current, Voltage,
· Crank the handle of the generator at a constant rate of approximately two revolutions per second and keep cranking. After about a minute release the handle and see what happens. The generator is easy to crank. It seems like the voltage was traveling at a constant rate. The charge seems to build.
· What happened to the amount of force necessary to crank the handle? What do you think was therefore happening to the amount of current flowing in the circuit? The generator supplies a constant voltage; the charge flowing through the circuit builds on the capacitor, which builds voltage opposed to that of the generator. This results in less voltage across the rest of the circuit and therefore less flow of current. Less current requires less energy so the cranking is easier.
· What happened after the handle was released and how could you possibly explain this? The bulb remained on. This is because the system stored some of the energy from when I cranked it.
· What evidence do you have that the capacitor in some way stored at least part of the energy you produced when you turned the crank? It continued after I stopped cranking. Think of charge being built on the capacitor, not current. The capacitor actually stores up the integral of the current with respect to time; since current is charge / time this integral has units of charge.
· Crank the handle of the generator at a rate that causes the bulb to burn, but neither very brightly or very dimly. Continue cranking the handle at the same rate regardless of what happens. After about a minute, release the crank and see what happens. The wire begins to glow.
· As you continue cranking, what do you notice about the force you have to exert, and what do you notice about the bulb? The thinner wire will offer more resistance to the flow of electrons so that fewer electrons will flow in this wire, which will tend to make the generator easier to crank. The bulb is dimmer.
· After you stop cranking, what happens to the generator and what happens to the bulb? The generator stops and the bulb is off.
· What happens to the voltage produced by the generator as you continue cranking? The voltage seems to remain the same consistent with the cranking.
· Does the voltage increase, decrease, or remain the same? How can you tell? You can tell if the voltage increases buy the rate at which you crank the generator. The bulb will be brighter if there is more voltage flowing.
· What happens to the current passing through the circuit as you continue cranking? The current continues to slowly increase.
· Does the current increase, decrease, or remain the same? How could you tell if you weren't looking at the light? How can you tell by looking at the light? You can tell is the current is increased by the rate at which you are cranking the generator. The faster the more current used. When you look at the light bulb the brighter the bulb light the faster the generator has been cranked.
· What therefore do you conclude happens to the voltage across the bulb as you continue cranking the capacitor-and-bulb circuit? The voltage remains constant as long as the cranking is constant. If the cranking is increased the voltage is increased and vice versa.
· Based on the force required to crank the generator, what happens to the current through the light bulb? Is this consistent with your answer to the preceding question? The more force the less voltage because it is harder to crank. The easier the cranking the more current. The number of volts created by the generator is proportional to the rate at which the handle is cranked. This is consistent to the preceding question.
· Based on what you think happens to the voltage across the bulb as you continue cranking, what do you think happens to the voltage across the capacitor? The voltage remains constant as long as it is cranked at a constant rate.
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