A box P and coil Q are in series with a variable-frequency 10 V AC source. Box P contains C=1 µF in series with 32 Ω; coil Q has L=4.9 mH and resistance 68 Ω. At the frequency of maximum current, find the impedances of P and Q and the voltages across them.
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Question

A box P and coil Q are in series with a variable-frequency 10 V AC source. Box P contains C=1 µF in series with 32 Ω; coil Q has L=4.9 mH and resistance 68 Ω. At the frequency of maximum current, find the impedances of P and Q and the voltages across them.

Options

G1 Physics · Accepted Answer

At maximum current the total series reactance is zero, so Xₗ=X꜀. Calculating each component impedance gives: for P, Z=77 Ω and V=7.7 V; for Q, Z=97.6 Ω and V=9.76 V. Hence option A.