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Asked in GUJCET 2015 · Behaviour of R, L and C separately
Idea: the charge on the capacitor follows the voltage, q = CV, and the current is the rate of change of that charge.
For V = V₀ sin ω t: I = (dq)/(dt) = C(dV)/(dt) = ω CV₀ cos ω t.
cos ω t = sin (ω t + π/2), so I = (V₀)/(X_C)sin (ω t + π/2) with X_C = 1/(ω C).
So the current leads the voltage by π/2.
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