Question

A series circuit with L = 0.12 H, C = 0.48 mF and R = 25 Ω is connected to a 220 V variable frequency power supply. At what frequency is the circuit current maximum?

(a) 79 Hz

(b) 19 Hz

(c) 21 Hz

(d) 93 Hz

This question was addressed to me in an online quiz.

I want to ask this question from AC Voltage Applied to a Series LCR Circuit topic in section Alternating Current of Physics – Class 12

Answer 1

Right choice is (c) 21 Hz

The best explanation: fr = \(\frac {1}{( 2\pi \sqrt {LC} )}\)

fr = \(\frac {1}{( 2 \times 3.14 \times \sqrt {0.12} \times 0.48 \times 10^{-3} )}\)

fr = 21Hz.