Electrostatic Potential and Capacitance · Question 43

A parallel plate capacitor of capacitance 1 μF is charged to a potential difference of 20 V. The distance between plates is 1 μm. The energy density between plates of capacitor is :

1. 1.8 103 J/m3
2. 2 102 J/m3
3. 2 10-4 J/m3
4. 1.8 105 J/m3

Answer

(1) 1.8 103 J/m3

Solution

Field between the plates: E = Vd = 2010-6 = 2 107 V/m

Energy density: u = 12 0 E2

u = 12 8.85 10-12 (2 107)2

u = 1.77 103 1.8 103 J/m3

Answer: (1)