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The average power absorbed by an impedance Z = 30 – j 70 Ω when a voltage V = 120∠0° is applied is _____________(a) 35(b) 37.24(c) 45(d) 50.25This question was addressed to me during an online interview.Origin of the question is Advanced Problems on Magnetically Coupled Circuits topic in chapter Resonance & Magnetically Coupled Circuit of Network Theory

Answer» RIGHT choice is (b) 37.24

To explain: The current through the impedance is given by,

I = \(\FRAC{V}{Z} = \frac{120∠0°}{30-j70}\)

= \(\frac{120∠0°}{76.16∠-66.8°}\)

= 1.576∠66.8° A

The average power is, P = 0.5VmImcos (θv – θi)

= 0.5(120) (1.576) cos (0 – 66.8°)

= 37.24 W.


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