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Phase difference
Intermediate
Relative shift between two oscillations.
Phase difference Δφ tells how far one oscillation is ahead of another. 0 = in phase, π = antiphase, π/2 = quadrature (like velocity and displacement).
AC current in an inductor lags voltage by 90°.
Δφ matters when combining waves.
In more detail
The phase difference between two oscillations is the difference in their phase angles. A phase difference of 180 degrees means they are exactly out of step.
Real-world uses
- Noise cancellation works by generating sound out of phase with the noise.
- Electrical engineers analyse the phase difference between voltage and current in AC circuits.
- Two loudspeakers driven from the same source can be out of phase, which reduces the sound at certain places in a room.
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Frequently asked questions
What is a phase difference of zero?
The oscillations are in phase and reinforce each other.
What is 180 degrees out of phase?
The oscillations are exactly opposite, and they cancel when added.
What does a phase difference of 180 degrees mean?
The two oscillations are exactly opposite, so when one is at its maximum the other is at its minimum.
Related topics in Oscillations & SHM
SHM acceleration · Angular frequency · Phase and phase constant · Phasor representation · Mass–spring system · Vertical spring