Question

In an alternating current circuit consisting of elements in series, the current increases on increasing the frequency of supply. Which of the following elements are likely to constitute the circuit?

• A. Only resistor
• B. Resistor and inductor
• C. Resistor and capacitor
• D. Only a capacitor

Answer 1

Answer: (C), (D)

The correct options are
C Resistor and capacitor
D Only a capacitor

We know,

Resistance (reactance) of the inductor and capacitor depends upon the frequency of the current.

$X_c=\frac{1}{2\pi fC}$

$X_l=2\pi fL$

$I_{RMS}=\frac{V_{RMS}}{\sqrt{R^2+(X_L-X_C{)}^2}}$

The RMS current for a resistor will not be affected because its impedance is independent of frequency whereas in the case of a resistor and inductor also, the current will decrease with an increase in frequency.

whereas the increase in frequency in the case of the capacitor leads to an increase in the RMS current because in this the impedance decreases with an increase in frequency.

Hence Option $\text{C}$ is correct answer.