Practice!

Sample Problem

A parallel-plate capacitor is connected across a potential difference of 40.0 V and stores 36.0 C of charge. The capacitor has a plate separation of 3.00 mm. The area of the plates is ___ m2.

(Assume ε0= 8.85 × 10-12  F/m)

Solution

C = Q/ΔV = 36 C ÷ 40 V = 0.9 F

C = ε0A/d

A = Cd/ε0= (0.9 F)(0.003 m)÷  8.85 ×10-12F/m

A = 3.05×108 m2