Question
A capacitor is made from two parallel plates separated by a distance d, and each has area A. The capacitor holds a charge Q. (a) What is the energy stored in the capacitor? (b) A mechanical force pulls the plates apart, without changing the stored charge, until they are 2d apart. Now how much energy is stored? (c) Explain the difference between (a) and (b).
Answers
Elena
(a)
C=εε₀A/d
Energy=Q²/2C
(b)
C₁=εε₀A/2d=C/2
Energy=Q²/2(C/2)= Q²/C
C=εε₀A/d
Energy=Q²/2C
(b)
C₁=εε₀A/2d=C/2
Energy=Q²/2(C/2)= Q²/C