Question

The work done in placing a charge of `8xx10^-18` coulomb on a condenser of capacity 100 micro-farad is
A. `3.1 xx 10^(-26) J`
B. `4 xx 10^(-10) J`
C. `32 xx 10^(-32) J`
D. `16 xx 10^(-32) J`

Answer 1

Correct Answer - B
`W = (1)/(2)Cv^(2) = (1)/(2)(q^(2))/(C )`
`= (1)/(2) xx ((8xx10^(-18))^(2))/(100xx10^(-6))`
`= (1)/(2) xx (64xx10^(-36))/(100xx10^(-6))`
`= 32 xx 10^(-32)J`