## Power Factor

A wattmeter, a voltmeter, and an ammeter are installed in an ac circuit, and read 1,000 W, 115 V, and 20 A respectively. What is the circuit's power factor?

Hint
Real Power, $$P$$ , is defined by:
$$P=V_{rms}\cdot I_{rms}\cdot cos\:\theta$$$$$P=V\cdot I\cdot cos\:\theta$$$
Solving for $$cos\:\theta$$ :
$$cos\:\theta=\frac{P}{V\cdot I}$$$Since $$cos\:\theta=pf$$ $$pf=cos\:\theta=\frac{P}{V\cdot I}=\frac{1,000}{115\cdot 20}=0.43$$$
0.43