Question

In Maxwell’s capacitance bridge for calculating unknown inductance, the various values at balance are, R1 = 300 Ω, R2 = 700 Ω, R3 = 1500 Ω, C4 = 0.8 μF. Calculate R1, L1 and Q factor, if the frequency is 1100 Hz.

(a) 240 Ω, 0.12 H, 3.14

(b) 140 Ω, 0.168 H, 8.29

(c) 140 Ω, 0.12 H, 5.92

(d) 240 Ω, 0.36 H, 8.29

I have been asked this question by my school principal while I was bunking the class.

I would like to ask this question from Advanced Problems on Measurement of Inductance using AC Bridges in section Measurement of Inductance and Capacitance of Electrical Measurements

Answer 1

Correct option is (b) 140 Ω, 0.168 H, 8.29

For explanation: From Maxwell’s capacitance, we have

R1 = \(\frac{R_2 R_3}{R_4} = \frac{300 × 700}{1500}\) = 140 Ω

L1 = R2 R3 C4

= 300 × 700 × 0.8 × 10^-6 = 0.168 H

Q = \(\frac{ωL_1}{R_1} = \frac{2 × π × 1100 × 0.168}{140}\) = 8.29.