alternating-currents Question 25

Question: Q. 14. The figure shows a series LCR circuit with L= 5.0H,C=80μF,R=40Ω connected to a variable frequency of 240 V source. Calculate

(i) The angular frequency of the source which drives the circuit at resonance.

(ii) The current at the resonating frequency.

(iii) The rms potential drop across the capacitor at resonance.

A [Delhi I, II, III 2012]

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Solution:

Ans. (i)

(ii) Current at resonance

Irms=VrmsR=24040 A=6 A1/2+1/2

(iii) Vrms across a capacitor

Vrms=IrmsXC =6×150×80×106 V =6×1064×103 V=60004 V=1500 V1/2

[CBSE Marking Scheme, 2012]



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