Question

In a series RC circuit, when the frequency and the resistance are halved, the impedance

• A. doubles
• B. is halved
• C. is reduced to one-fourth
• D. cannot be determined without values

Answer 1

The correct option is D cannot be determined without values

Capacitive reactance is given by $X_C=\frac{1}{2\pi fC}$
where $f$ is the frequency.
Impedance of the RC circuit $Z=\sqrt{R^2+X_C^2}=\sqrt{R^2+\frac{1}{4{\pi }^2{f}^2{C}^2}}$
If frequency and resistance are halved, we cannot determined unless the values are given.