When a.c. source is connected across a pure capacitor, the correct phase relation between current…
When a.c. source is connected across a pure capacitor, the correct phase relation between current $\left(\mathrm{i}_{\mathrm{c}}\right)$ and voltage $\left(\mathrm{e}_{\mathrm{c}}\right)$ is shown in figure
(B)
(C)
(D)
(A)
Solution
Conceptual question. The current leads the voltage by $\frac{\pi}{2}$ radians.
Ac voltage source, $\mathrm{V}=\mathrm{V}_0 \sin (\omega \mathrm{t})$
Charge at a given moment on the capacitor, $\mathrm{q}=\mathrm{CV}$
The current through the circuit: $\frac{\mathrm{dq}}{\mathrm{dt}}=\left(\omega \mathrm{CV}_0\right)=\cos (\omega \mathrm{t})$
As cos leads the $\sin$ function by $\frac{\pi}{2}$ radians.
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