Question

The impedance of an RC series circuit is 12 Ω at f = 50 Hz. At f = 200 Hz, the impedance will be?

(a) More than 12

(b) Less than 3

(c) More than 3 Ω but less than 12 Ω

(d) More than 12 Ω but less than 24 Ω

The question was posed to me during an interview.

My question is taken from Advanced Problems on Application of Laplace Transform topic in section Application of the Laplace Transform in Circuit Analysis of Network Theory

Answer 1

Correct answer is (c) More than 3 Ω but less than 12 Ω

To explain: We know that the impedance Z, is given by

Z = R^2 + \(X_C^2\)

When f is made four times, XC becomes one-fourth but R remains the same.

So, the impedance is more than 3 Ω but less than 12 Ω.