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In an ideal inductor, what is the phase relation between voltage and current?

Voltage leads current by a quarter cycle.

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  1. Voltage leads current by 90 degrees ✔
  2. Voltage lags current by 90 degrees
  3. They are in phase

Why: OpenStax College Physics says that in an inductor the voltage leads the current by one-fourth of a cycle, or 90 degrees. Inductive reactance is 2 pi f L, so it rises with frequency.

Huh, didn't know that: Because X_L = 2 pi f L, doubling the frequency doubles an inductor's reactance.

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References

Answer: Voltage leads current by 90 degrees. OpenStax College Physics says that in an inductor the voltage leads the current by one-fourth of a cycle, or 90 degrees. Inductive reactance is 2 pi f L, so it rises with frequency.

  1. Physics LibreTexts (OpenStax College Physics), 23.2 Reactance, Inductive and Capacitive phys.libretexts.org/Bookshelves/College_Physics/College_Physics_1e_(OpenStax)/23:_Electromagnetic_Induction_AC_Circuits_and_Electrical_Technologies/23.02:_Reactance_Inductive_and_Capacitive
    the voltage leads the current by one-fourth of a cycle
    Checked 2026-10-10.

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