If the electric field inside a capacitor exceeds the dielectric strength of the

Question

If the electric field inside a capacitor exceeds the dielectric strength of the dielectric between its plates, the dielectric will break down, discharging and ruining the capacitor. Thus, the dielectric strength is the maximum magnitude that the electric field can have without breakdown occurring. The dielectric strength of air is 3.0 106 V/m, and that of neoprene rubber is 1.2 107 V/m. A certain air-gap, parallel plate capacitor can store no more than 0.039 J of electrical energy before breaking down. How much energy can this capacitor store without breaking down after the gap between its plates is filled with neoprene rubber?

Explanation / Answer

Stored energy in a capacitor E = CV^2 / 2 [J].

Q=CV

C=ORA/D
So energy is proportional to capacitance and the square of voltage.
Capacitance is proportional to the dielectric constants which are
not given in the problemA = 1.00059, 0 = 6.7.
E = 0.07* (6.7 / 1.00059) * (12 / 3)^2 =7.5

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