The power factor of an AC circuit is defined as
Correct answer: B. the cosine of the phase angle between current and voltage
- A. the ratio of peak to rms current
- B. the cosine of the phase angle between current and voltage
- C. the ratio of frequency to reactance
- D. the product of voltage and current
Explanation
True power is V times I times cos theta, so the power factor measures how much of the apparent power is actually being converted to useful work. It is 1 for a purely resistive circuit and zero for a pure reactance. Industrial users correct a poor power factor with capacitors, because a low value means large currents and heavy cable losses for the same useful power.
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About AC Through Resistor, Capacitor and Inductor
Alternating current through a resistor, capacitor and inductor involves phase relationships between voltage and current, reactance, impedance and energy transfer. A resistor keeps voltage and current in phase, while a capacitor and inductor produce opposite phase shifts, a distinction used in circuit diagrams and numerical calculations.
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