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?
Expand 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
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