Air isn't a perfect electric insulator, but it has a very high resistivity. Dry air has a resistivity of approximately 3 x 10^13 Ù x m. A capacitor has square plates 10 cm on a side separated by 1.2 mm of dry air.

Question

If the capacitor is charged to 250 V, what fraction of the charge will flow across the air gap in 1 minute? Make the approximation that the potential difference doesn't change as the charge flows.

Answer 1

Calculate C, the capacitance
Q = charge = C V

R = resistance = 3*10^13 *.0012/(.1*.1)
i =V/R
change in Q = i t = (V/R)*1*60

fraction = change in Q / Q

Answer 2

Can you clarify on this part:

Calculate C, the capacitance
Q = charge = C V