alleryStart learning →In an AC circuit with a pure CAPACITOR, the current
Ais in phase with voltage
Bleads voltage by 90 degrees
Clags voltage by 90 degrees
Dleads voltage by 180 degrees
Answer & Solution
Correct answer: B. leads voltage by 90 degrees
1. Capacitor: $i_C = C\,dv/dt$.
2. If $v(t) = V_m\sin(\omega t)$, then $i_C(t) = \omega C V_m \cos(\omega t) = \omega C V_m \sin(\omega t + 90^\circ)$.
3. So CURRENT LEADS VOLTAGE by 90°.
4. Mnemonic: 'ICE' — in a capacitor (C), current (I) precedes voltage (E).
5. Option C is the INDUCTOR behavior. Other options are wrong.
_Source: Tony Kuphaldt, "Lessons in Electric Circuits — AC", Vol II, Ch 4 (Capacitor phase)._
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