Question

A capacitor is connected to an AC generator. As the generator's frequency is increased, what happens to the current in the capacitor? A)The current increases B)The current decreases C)The current does not change.

Answer 1

Answer:

A) The current increases

Explanation:

In the DC limit (that means, very low frequency of the generator), the capacitor acts as an open circuit. In fact, a capacitor consists of two parallel plates which are separated from each other: this means that the current cannot flow through it, but it can only flow through the rest of the circuit.

In the case of a direct current (DC), therefore, the current in the circuit must be zero. For an AC current with very low frequency, the current is still very low, because the polarity of the generator changes direction not very often, so there is still enough time for the capacitor to "block" the current. However, when the frequency of the generator is increased, the polarity changes so fast that the current in the circuit can flow without having time of "hitting" the capacitor, so it has almost no effect and the current in the circuit is maximum.