Question

A series RLC circuit has R = 50 Ω, L = 0.01 H and C = 0.04 × 10^-6 F. System voltage is 100 V. At this frequency, the circuit impedance is?

(a) 50 – j2.5 Ω

(b) 50 – j2.8 Ω

(c) 50 + j2.5 Ω

(d) 50 + j2.8 Ω

The question was posed to me during an interview.

My query is from Problems of Series Resonance Involving Frequency Response of Series Resonant Circuit topic in section Resonance & Magnetically Coupled Circuit of Network Theory

Answer 1

The correct option is (a) 50 – j2.5 Ω

Easy explanation: Z = R + j (ωL + \(\frac{1}{ωC}\)) = 50 + j \(\left(2π × 7937.81 × 0.01 – \frac{1}{2π×7937.81×0.04×10^{-6}}\right)\) = 50 – j2.5 Ω.