Question

A small signal voltage $V\left(t\right)=V_0\sin \omega t$ is applied across an ideal capacitor $C$. Then:

• A. current $I\left(t\right)$, lags voltage $V\left(t\right)$ by ${90}^o$
• B. over a full cycle the capacitor $C$ does not consume any energy from the voltage source
• C. current $I\left(t\right)$ is in phase with voltage$V\left(t\right)$
• D. current $I\left(t\right)$ leads voltage $V\left(t\right)$ by ${180}^o$

Answer 1

Answer: (B)

Power, $P=V_{rms}{I}_{rms}cos\varphi$

$\Rightarrow cos\varphi =0$....(as $\varphi ={90}^0$ between $I_{rms}$ and $V_{rms}$ across a capacitor)

Therefore, power consumed $=0$ in one complete cycle across a capacitor.