Question

The power factor in a circuit connected to an AC power supply has a value which is:

• A. unity when the circuit contains only inductance
• B. unity when the circuit contains only resistance
• C. zero when the circuit contains an ideal resistance only
• D. unity when the circuit contains an ideal capacitance only

Answer 1

Answer: (B)

Power factor, $ \cos \phi =\frac{R}{Z} $
When circuit contains only resistance, then
$ Z=R $
$ \therefore $ $ \cos \phi =\frac{R}{R}=1 $