A capacitor consists of two 7.0cmdiameter circular plates separated by 1.0 mm. The plates are charged to 160 V , then the battery is removed.
1) How much energy is stored in the capacitor?
2) How much work must be done to pull the plates apart to where the distance between them is 2.0 mm?
1 Answers

Part 1
Part 2
Є0 Dielectricconstant A Areaofplate d Distancebetweenplates V  Voltage D Diameterofcircularplate Given: d = 1 mm = 1 × 103 m D = 7 cm 7 x 102 m = V = 160 V For circular plate, Area is calculated by. 2 A = πr2 Ꭰ = π 2 = π 7 x 10 2 2 2 m The Capacitance of parallel Plate capacitor is given by, C= (8.85 × 1012 F) 1 × 103 m ε0 A d 2 7 × 102 2 m 11 F = 3.4 × 10 = 34pF The energy stored in parallel plate Capacitor is given by, = 1 1 U = CV2 2 (3.4 × 10−11F) (160 V)2 = 4.35 × 107FV2