1.

In Maxwell’s Bridge, as shown in the figure below, the values of the resistance R1 and inductance L1 of a coil are to be calculated after the bridge is balanced. The values are?(a) 375 Ω and 75 mH(b) 75 Ω and 150 mH(c) 37.5 Ω and 75 mH(d) 75 Ω and 75 mHThis question was addressed to me during a job interview.This intriguing question comes from Advanced Problems on Measurement of Inductance using AC Bridges in division Measurement of Inductance and Capacitance of Electrical Measurements

Answer»

Correct option is (a) 375 Ω and 75 mH

The best I can explain: APPLYING the usual BALANCE condition relation,

Z1 Z4 = Z2 Z3

We have, (R1 + jL1 ω) \(\frac{R_4/jωC_4}{R_4+1/jωC_4}\) = R2 R3

Or, R1 R4 + jL1 ωR4 = R2 R3 + j R2 R3 R4 C4 ω

∴ R1 = 2000 × \(\frac{750}{4000}\) = 375 Ω

∴ L1 = 2000 × 750 × 0.5 × 10^-6

= 75 mH.



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