Question

A 12 pF capacitor is connected to a 50 V battery. How much electrostatic energy is stored in the capacitor ? If another capacitor of 6 pF is connected across the combination, find the charge stored and potential difference across each capacitor.

Answer 1

Energy stored =
`1/2CV^(2) = 1/2 12 xx 10^(-12) xx 50^(2) J`
`= 1.5 xx 10^(-8) J`
If, `1/(C_(eq)) = (1/12+ 1/6) pF`
`1/(C_(eq)) = 1/4 pF , C_(eq) = 4 xx 10^(-12)F`
`Q = C_(eq) V = 4 xx 10^(-12)C xx 50= 200 xx 10^(-12)C`
Voltage across 12 pF capacitor `= Q/C = (200 xx 10^(-12))/(12 xx 10^(-12)) =16.67V`
Voltage across `16pF` capacitor `= (200 xx 10^(-12))/(16 xx 10^(-12)) = 33.33 V`.