SESKStuff Everyone Should Know
SESK: Stuff Everyone Should Know · sesk.info/hame-series-resonance-z

At resonance, what is the impedance of a series RLC circuit?

Minimum, equal to R.

Start playing free

  1. Minimum, equal to the resistance ✔
  2. Maximum, equal to the reactance
  3. Zero, no matter what the resistance is

Why: At series resonance the inductive and capacitive reactances cancel, leaving the impedance as just R. Current is therefore at its maximum at that frequency.

Huh, didn't know that: The series impedance curve is U-shaped, bottoming out at resonance.

The dad joke
Where do electricians go to get their supplies? The Ohm Depot.
Like this card?
Play the game

References

Answer: Minimum, equal to the resistance. At series resonance the inductive and capacitive reactances cancel, leaving the impedance as just R. Current is therefore at its maximum at that frequency.

  1. Engineering LibreTexts, AC Electrical Circuit Analysis, 8.4 Summary eng.libretexts.org/Bookshelves/Electrical_Engineering/Electronics/AC_Electrical_Circuit_Analysis%3A_A_Practical_Approach_(Fiore)/08%3A_Resonance/8.4%3A_Summary
    the reactances cancel, leaving the series impedance as \(R\).
    Checked 2026-10-11.

Think this answer is wrong? Tap "Challenge this answer" on the card in the game and tell us why.

Test yourself in the game

Ham RadioAt resonance, what impedance does a parallel LC circuit present?Ham RadioIn a resonant circuit, what does a higher Q do to the bandwidth?Ham RadioAt the half-power points of a resonant circuit, the current is what fraction of its maximum?

That's stuff everyone should know.