An inductor 20 mH, a capacitor 50μF, and a resistor 40Ω are connected in series across a source of emf V=10sin(340t). The power loss in the AC circuit is:
A
0.67 W
B
0.78 W
C
0.89 W
D
0.46 W
Step-by-Step Solution
From the given voltage equation V=10sin(340t), the peak voltage is Vm=10 V and the angular frequency is ω=340 rad/s.
The inductive reactance is XL=ωL=340×20×10−3=6.8Ω.
The capacitive reactance is XC=ωC1=340×50×10−61=0.0171≈58.82Ω.
The impedance of the series LCR circuit is Z=R2+(XC−XL)2=402+(58.82−6.8)2=402+52.022≈1600+2706=4306≈65.62Ω.
The RMS current is Irms=ZVrms=ZVm/2=2×65.6210.
The power loss in the circuit is dissipated only in the resistor and is given by P=Irms2R .
P=(2×65.6210)2×40=2×4306100×40=43062000≈0.46 W.
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