Calculation of electrostatic energy in 12‌pF capacitor
Total charge stored in combination
Potential difference across each capacitor
Energy stored, in the capacitor of capacitance 12 pF ,
U‌=‌

1

2

C1V2
‌=‌

1

2

×12×10−12×50×50J
‌=1.5×10−8J
C= Equivalent capacitance of 12‌pF and 6‌pF, in series, is given by
‌‌

1

C‌eq ‌

=‌

1

12

+‌

1

6

=‌

1+2

12

∴‌‌C‌eq ‌‌=4‌pF
∴ Charge stored across each capacitor
q‌=CeqV
‌=4×10−12×50C
‌=2×10−10C
Charge on each capacitor 12‌pF as well as 6‌pF
∴ Potential difference across capacitor C1
∴V1=‌

2×10−10

12×10−12

‌ volt ‌=‌

50

3

V
Potential difference across capacitor C2
∴V2=‌

2×10−10

6×10−12

‌ volt ‌=‌

100

3

V