Question

A parallel-plate capacitor consists of two square plates 18 Cm on a side, spaced 0.50 mm apart with only air between them. What is the maximum energy that can be stored by the capacitor?

Answer 1

Figure capacitance. Use your formula.

Then figure the maximum voltage that can be on the plates in dry air (consider breakdown voltage of air, and spacing).

Then, Energy= 1/2 C V^2

Let me know if you have a problem on this.