What is the resonant frequency of circuit shown below? Where R = 10 Ω, L1 = L2 = 20 mH, Mutual Inductance M = 5 mH, C = 0.05 µH. [Figure description: An AC source Vs drives a circuit containing two magnetically coupled coils L1 and L2 wound on the same core (cylinder), with mutual inductance M shown by a curved double arrow between them. L1 and L2 are connected in series with the source, and a capacitor C is connected across (in parallel with) the junction between the coils.]
- A. 4.18 kHz
- B. 2.88 kHz
- C. 5.18 kHz
- D. 3.18 kHz
Answer: C. 5.18 kHz
Explanation: Excluded from evaluation by ISRO due to ambiguity in coupled coil polarity. Equivalent inductance Leq = L1 + L2 ± 2M = 40 ± 10 mH; resonant frequency f0 = 1/(2π√Leq·C) ≈ 5.18 kHz.