AC through Pure Capacitor:
The current flowing through capacitor is given by
i = C dv /dt
= C dv / dt (Vm sin ωt )
= C Vm ω cos ωt
Vm/(1/ ωC) sin( ωt +(π/2))
= Vm / XC sin ( ωt +( π/2) )
Where X c = 1/ ωC = Capacitive reactance in ohm.
Figure : Pure Capacitive Circuit
If we put Im = V m / X C , then
i = I m sin (ωt + (π/2) )
Here, we may see that current i leads the applied voltage by π/2 .