Engineering Board Exam Reviewer · RC Circuits · easy
In a purely capacitive ac circuit, the current
- lags the voltage by 90°
- is in phase with the voltage
- leads the voltage by 45°
- leads the voltage by 90°
Answer
D. leads the voltage by 90°
Solution
A capacitor's current is proportional to the rate of change of its voltage, so the current reaches each peak a quarter cycle before the voltage does: the current leads by 90° (ICE: I leads E in a capacitor).
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