Alternating Current - Result Question 19
19. In an electrical circuit $R, L, C$ and an a.c. voltage source are all connected in series. When $L$ is removed from the circuit, the phase difference between the voltage the current in the circuit is $\pi / 3$. If instead, $C$ is removed from the circuit, the phase difference is again $\pi / 3$. The power factor of the circuit is :
[2012]
(a) $1 / 2$
(b) $1 / \sqrt{2}$
(c) 1
(d) $\sqrt{3} / 2$
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Answer:
Correct Answer: 19. (c)
Solution:
- (c) $-MM^{-OrO}$ when $L$ is removed from the circuit
when $C$ is remove from the circuit
net impedence $Z=\sqrt{R^{2}+(X_L-X_C)^{2}}=R$
power factor $\cos \phi=\frac{R}{Z}=1$
