Question

Calculate the power factor of the circuit shown in figure

• A. $0.2$
• B. $0.4$
• C. $0.8$
• D. $0.6$

Answer 1

Answer: (C)

Resistance of the circuit,
$R=R_{1}+R_{2}=40 \, \Omega +40 \, \Omega =80 \, \Omega $
Impedance of the circuit,
$Z=\sqrt{R^{2} + \left(X_{L} - X_{C}\right)^{2}}=\sqrt{\left(80\right)^{2} + \left(100 - 40\right)^{2}}$
$=\sqrt{\left(80\right)^{2} + \left(60\right)^{2}}=100 \, \Omega $
Power factor, $cos \phi=\frac{R}{Z}=\frac{80}{100}=0.8 \, $