Extra exam question E5B09
Subelement E5, ELECTRICAL PRINCIPLES· Group E5B
What is the relationship between the AC current through a capacitor and the voltage across a capacitor?
- A.Voltage and current are in phase
- B.Voltage and current are 180 degrees out of phase
- C.Voltage leads current by 90 degrees
- D.Current leads voltage by 90 degrees (correct answer)
WhyIn a capacitor, the AC current leads the voltage by 90 degrees. In a capacitor, current has to flow to build up charge before the voltage across the capacitor can rise in response, so the current leads the voltage by 90 degrees, the standard phase relationship for an ideal capacitor, answer D. Voltage and current aren't in phase or 180 degrees apart in a purely capacitive circuit, and it's the current that leads, not the voltage.
Published 2026-08-28 · Last updated 2026-08-28 · Question text is verbatim from the 2024-2028 NCVEC Element 4 pool (public domain); the explanation above is original writing, see our methodology.
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