Homework SourseTwo hollow metal spheres are concentric with each other The
Two hollow metal spheres are concentric with each other. The inner sphere has a radius of 0.156 m and a potential of 84.0 V. The radius of the outer sphere is 0.158 m and its potential is 81.0 V. If the region between the spheres is filled with Teflon, find the electric energy contained in this space.
Solution
Potentialdifference V = Vinner - Vouter = 84.0 - 81.0 = 3.0 V
The system works as a spherical capacitorwith capacitance C = 4* rinner * router / (router - rinner)
= permittivityof teflon = 1.86 *10-11
C = 4 *3.14 * 1.86 * 10-11 * 0.156 * 0.158 / ( 0.158 -0.156) = 2.88 *10-9 F
Energy stored betweenspheres = energy stored oncapacitor = (1/2) * C *V2
E = 0.5* 2.88 * 10-9 *3.02 = 1.296 *10-8 J = 12.96 nJ
E = 0.5* 2.88 * 10-9 *3.02 = 1.296 *10-8 J = 12.96 nJ
