Question

if the charge on a capacitor is increased by 2C the energy stored in it increase by 21% the original charge on capacitor is

Answer 1

Energy stored in a capacitor U = CV²/2

U = Q²/2C     ( Since V = Q/C )

Initial Q₁ = Q

Final Q₂ = Q + 2

Initial U₁ = 100 J

Final U₂ = 121 J

U is proportional to Q² at constant C

U₁/U₂ = [Q₁/Q₂]²

100/121 = [ Q / (Q + 2) ]²

10/11 = Q / Q+2

10Q + 20 = 11Q

Q = 20 C