A capacitor is in its basic version is two electrical conductor plate or body separated by some insulating medium. It stores energy in the form of electrical charge. [Rectifier / Inverter / Capacitor / Inductor details].

*A capacitor can be represented by an insulating layer between two conductor plates (armatures)*

## Capacitor with Direct Voltage:

If a direct voltage is applied across the terminals the armatures are charged with a quantity Q of electricity.Energy W is stored and an electrical field E is established in the dielectric. As soon as the capacitor is charged, the current stops flowing (except for a very small quantity of leakage current).

C: capacitor capacitance in Farad (F)

ε • = dielectric permittivity in F/m

εr = relative permittivity of the insulating material

ε0 = 8.85 • 10-12 F/m

*Capacitor blocks current in DC voltage. Though there might be some leakage current- depends upon the voltage level & di-electric medium.*

## Capacitor with AC voltage

Energy is stored and restored 100 or 200 times per second depending on the network frequency. A current flows, rather than transitory it is periodic, corresponding to the capacitor charge and discharge.

i = dQ/dt et Q = C • V

i = C • dV/dt = Cω V0 cos ωt

As an rms value

I = C ω V

i leads v by 1/4 of a cycle

*Capacitor let pass the current in AC voltage but with a shift of phase between voltage and current. The voltage is lag behind the current*