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RL Circuits - Engineering

Q1:

A 1.2 k resistor is in series with a 15 mH coil across a 10 kHz ac source. The magnitude of the total impedance is

A 152.6 

B 1,526 

C 1,200 

D 942 

ANS:B - 1,526 

R = 1.2k ohm = 1.2 * 1000 = 1200 ohm
L = 15mH = 15 * 10^-3 = 0.015H
F = 10kHz = 10 * 1000 = 10,000 Hz
Impedance Z = (?)

XL = 2 * fL
XL = 2 * 3.14 * 10,000 * 0.015,
XL = 942..

Impedance Z = √ (R^2 + XL^2).
Z = √ (1200^2 + 942^2),
Z = 1525.86.
Ans is Z = 1526.