BITSAT 2015 Solved Question Paper

From the figure.
The net charge shared between the two capacitors
Q' = Q2−Q2 = 4CV - CV = 3CV
Q1 = C1V1 = CV

Q2 = C2V2 = (2C) (2C) = 4CV
The two capacitors will have some potential, say V'.
The net capacitance of the parallel combination of the two capacitors
C' = C1+C2 = C + 2C + 3C
The potential of the capacitors
V' =

Q′

C′

=

3CV

3C

= V
The electrostatic energy of the capacitors
E' =

1

2

C′V′2 =

1

3

(3C)V2 =

3

2

CV2