64) We are asked to find the answer choice that does not describe a situation where the bulb would light. In order to get the bulb to light, we need to induce a current in the wire. According to Faraday's Law, when there is a change in magnetic flux over a coil, it will induce a current. This means we want to continually be changing the magnitude of the magnetic field's affect on the circuit. There are three main ways to change the magnetic flux.
Let's take a look at the answer choices.
Choice A: This is a tricky answer choice. Many people will read that the handle is rotated 90 degrees and immediately skip over to the next choice. If we were to rotate the coil, this would, indeed, create a change in magnetic flux, which would cause an induced current. However, this is not what we are doing. The answer choice will not create an induced current because we are not rotating the coil; we are rotating the handle. This should be the correct answer, but let's check the other answers to confirm that this is correct.
Choice B & C: Choice B says that we can raise the handle away from the coil. This will cause an induced current because we are changing the intensity of the magnetic field. Lowering the handle toward the coil should also cause an induced current because, for the same reason as Choice B, we are changing the intensity of the magnetic field. So neither Choice B nor C will be our answer.
Choice D & E: Decreasing the resistance of the coil will change the magnitude of the magnetic field produced by the coil, so it will produce magnetic flux. With the same reasoning, increasing the resistance of the coil will also change the magnitude of the magnetic field produced by the coil. So both of these choices will create an induced current, and therefore, Choice D or E cannot be our answer.
Answer: A
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