Question

A coil of inductive reactance $31\, \Omega$ has a resistance of 8 $\Omega$. It is placed in series with a condenser of capacitative reactance $25 \,\Omega$. The combination is connected to an a.c. source of 110 V. The power factor of the circuit is :-

• A. 0.33
• B. 0.56
• C. 0.64
• D. 0.8

Answer 1

Answer: (D)

0.8

Answer 2

Power factor $=\cos \,\phi=\frac{ R }{| Z |}=\frac{8}{\sqrt{8^{2}+(31-25)^{2}}}$
$=\frac{8}{\sqrt{8^{2}+6^{2}}}=\frac{8}{10}=0.8$