Two capacitors are identical, except that one is empty and the other is filled with a dielectric (k = 4.2). The empty capacitor is connected to a 14 -V battery. What must be the potential difference across the plates of the capacitor filled with a dielectric so that it stores the same amount of electrical energy as the empty capacitor?

1 answer

Capacitance of 1 = C
Capacitance of 2 = k*C

Energy = (1/2)*C*V^2

As per the question,

(1/2)*(C1)*(V1)^2 = (1/2)*(C2)*(V2)^2
=> C*(14)^2 = k*C*(V2)^2

Solve for V2