Question

A capacitor has two overlapping plates of width 4.9 m and length 3.5 m separated by 1.3 cm. A dielectric of dielectric constant ê = 58.0 fills the space between the plates. If this capacitor is connected to a 35 V battery, how much energy is stored in the capacitor when it is charged to 35 V?
I first found the capacitance using the eqn C=k*(8.854*10^-12)
*Area/distance and found C=6.67*10^-7F but when i substitute C in the equation E=1/2*CV^2 i don't get the correct answer(0.000415J.

Answer 1

Sorry i mean k=58 and the values i substitued into the eqn were C=58*(8.854*10^-12)*(3.5m*4.9m)/0.013m which gave me C=6.77*10^-7F

Answer 2

I agree with your calculation of C. Try that with
E = (1/2) C V^2
and you should get the correct energy value.