When the ac generator in the figure(Figure 1) operates at high frequency, is the

Question

When the ac generator in the figure(Figure 1) operates at high frequency, is the rms current in the circuit greater than, less than, or the same as when the generator operates at low frequency? Greater than less than the same as Choose the best explanation from among the following: The capacitor has no resistance, and therefore the resistance of the circuit is the same at all frequencies. As a result the current is the same at all frequencies. More current flows at high frequency because in that limit the capacitor is like a short circuit and current has two parallel paths to flows through. Less current flows at high frequency because in that limit the capacitor is like an open circuit and current has only one path to flow through.

Explanation / Answer

Capacitace reactance (Xc) of a capacitor at any particular frequency is given by:

Xc = 1/C where C is the capacitance of the capacitor.

Now at very high the Xc (effective resistance offered by a capacitor ) will be negligilble and the capacitor will be like a short circuit and thus the equivalent resistance of the two parallel resistors (R each) will be R/2, while in the case when the is very low then Xc will be very high and almost all current will flow through the upper part of the circuit and thus offering net effective resistance of R. Hence in the former case the rms current will be higher than in the latter case.

So Part-A:---------- correct choice is option 1 i,e greater than

and Part B:------- correct choice will be option 2.

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