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Phase angle
Intermediate
Angle between voltage and current.
tanφ = (X_L−X_C)/Rφ is the angle between voltage and current: positive for inductive, negative for capacitive circuits, zero at resonance. It decides power transfer.
φ = 53° for R = 30, net X = 40.
Phase has a sign.
In more detail
The phase angle φ in an AC circuit is the angle between the voltage and current, given by tan φ = (XL − XC)/R. Positive values mean the voltage leads, and negative values mean it lags.
Real-world uses
- Power engineers monitor phase angles to assess power factor.
- Phase measurement is used in control systems.
- Engineers calculate the phase angle of a circuit to see whether it behaves more like a resistor, inductor or capacitor.
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Frequently asked questions
What does a positive phase angle mean?
The voltage leads the current, which is typical of inductive circuits.
What if X_L equals X_C?
The phase angle is zero, so the circuit behaves as a pure resistor.
What is a positive phase angle?
It means the voltage leads the current, so the circuit is more inductive than capacitive.
Related topics in AC Circuits & EM Waves
Inductor in AC · Capacitor in AC · LCR series circuit · Series resonance · Quality factor in LCR · Bandwidth