Answer to Question #304871 in Physics for Shane

Question

A parallel plate capacitor having a plate area of 0.70 m2 and a plate separation of 1.0 mm is connected to a source with a

voltage of 50 V. Find the capacitance, the charge on the plates, and the energy of the capacitor when there is air

between the plates.

Answer 1

The capacitance

$$C=\frac{\epsilon_0 A}{d}\\ =\frac{8.85*10^{-12}*0.70}{0.001}=6.2*10^{-9}\:\rm F$$

The charge on the plates

$$q=CV=6.2*10^{-9}*50=3.1*10^{-7}\:\rm C$$

The energy of the capacitor

$$W=\frac{CV^2}{2}=\frac{6.2*10^{-9}*50^2}{2}=7.8*10^{-6}\:\rm J$$