Energy Stored in Capacitor Formula in Joule, Watt-Hour

Capacitor energy formula:

The energy stored in capacitor E(Wh) in watt-hours is equal to the 0.000148 times of capacitance C(F) and the voltage V(V) in volts square. Hence the energy stored in the capacitor can be written as,

E(Wh) = 0.000148 x C(F) x V2(V)

In Kilowatt-hour,

E(kWh) = 0.000000148 x C(F) x V2(V)

Energy = 0.5 x capacitance x voltage2

While the energy stored in the capacitor formula in joules means

E(J) = 0.5 x C(F) x V2(V)

Here, applies the rated capacitance value as

C(F) = ϵ A / d

Energy E(wh) = 0.000148 x ϵ x A x V2(V) / d

Here A = surface area of the plates in meter square.

D = Distance between the plates in meter.

Look at the above formula, the energy stored in the capacitor is directly proportional to the square of the applied voltage & the surface area and inversely proportional to the distance between the two electrodes.

Hence when you decrease the distance between the plates, the capacitor stores more energy.

Also, the energy stores in the capacitor in terms of electric charge the formula can be written as,

The energy in capacitor E(J) = 0.5 x V3(V) / Q(c)

Here Q(c) is the charges inside the capacitor in the coulomb.

Energy Stored in AC Capacitor Formula:

The energy stored in the capacitor is called reactive energy. The instant transfer of reactive energy is called reactive power. The maximum energy supplied by a capacitor E(VARH) in volt amp reactive hour is equal to the 375 times of the capacitance in microfarad, frequency in Hz, and the square of the voltage in volts. The energy stored in a capacitor formula will be,

E(VARH) = 375 x C x f x V2


Let us calculate energy stored in the 250 Milli farad capacitor while applying 240 V across the plates.

E(J) = 0.5 x 250 x 10-3 x 240 x 240

= 7200 Joules.

For converting energy stored in the capacitor in Wh (Watt-Hour),

E(Wh) = 7200 / 3600 = 2 Wh.

Also, in kWh,

W(kWh) = 2 / 1000 = 0.005 kWh.


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