Q124 / 180 · NEET 2016 (Phase 1) · Physics

A small signal voltage $V (t) = V_{0} \sin ω t$ is applied across an ideal capacitor $C$ :

A
Current $I(t),$ lags voltage $V(t)$ by $90^{o}$
Correct answer
B
Over a full cycle the capacitor $C$ does not consume any energy from the voltage source
C
Current $I(t)$ is in phase with voltage $V(t).$
D
Current $I(t)$ leads voltage $V(t)$ by $180^{o}$

Solution

In capacitor current leads the voltage by $ϕ = \frac{π}{2}$ phase. Average power dissipated in AC circuit is given by

$P_{a v} = V_{r m s} I_{r m s} \cos (ϕ)$

In capacitor $ϕ = \frac{π}{2}$ so $\cos (\frac{π}{2})$ is zero.

Hence, the correct answer is option: 'B'.