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Inductor in AC
Intermediate
Current lags voltage by 90°.
X_L = ωLThe inductor's emf opposes the current change, so current lags voltage by 90°. Reactance X_L = ωL increases with frequency.
L = 0.1 H at 50 Hz: 31.4 Ω.
Passes DC but blocks high-frequency AC.
In more detail
An inductor in an AC circuit has its voltage leading the current by 90 degrees. Its reactance X_L = ωL increases with frequency, so it opposes high-frequency currents more.
Real-world uses
- Inductors are used to block high frequencies in filters.
- Ballasts in fluorescent lamps use inductors to limit current.
- A transformer's coil or an inductor in a lighting ballast limits the AC current through its reactance.
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Frequently asked questions
What is reactance?
The opposition to AC current from an inductor or capacitor, measured in ohms.
Does an inductor dissipate power?
Ideally no, because it stores and returns energy each cycle.
Why does current lag in an inductor?
The changing current induces a back emf that opposes it, so the current reaches its peak a quarter cycle after the voltage.
Related topics in AC Circuits & EM Waves
Average power in AC · Phasors · Resistor in AC · Capacitor in AC · LCR series circuit · Phase angle