Shortcut Methods

JEE Numerical:

1. An LCR circuit has L=1H, C=100μF, and R=10Ω. Calculate the resonant frequency.

fr=12πLC=12π(1)(100×106)

fr=159.2Hz

2. A 100mH inductor, a 10μF capacitor, and a 10Ω resistor are connected in series to a 100V, 50Hz AC source.

Z=R2+(XLXC)2

Z=102+(2π50×0.11/2π50×100×106)2

Z=100+250010=44.7Ω

I=EZ=10044.7=2.24A

CBSE Numerical:

1. A 50Hz alternating current source of 100V is connected to a series LCR circuit containing R = 100Ω, L = 0.2H, and C = 100μF. Determine the impedance of the circuit.

Z=R2+(XLXC)2

Z=1002+(2π50×0.21/2π50×100×106)2

Z=10000+10010=99.9Ω

2. Calculate the resonant frequency of a series LCR circuit having L=10mH, C=400μF, and R=20Ω.

fr=12πLC=12π(10×103)(400×106)

fr=79.6Hz



Table of Contents