Work performed when a point charge `2xx10^(-8)C` is transformed from infinite to a point at a distance of `1cm` from the surface charge density `sigma=10^(-8)C//cm^(2)`

Options

A. `1.1xx10^(-4)J`
B. `11xx10^(-4)J`
C. `0.11xx10^(-4)J`
D. `113xx10^(-4)J`

Answer

B

Explanation

Potential at a distance 2cm from its centre
`=(Q)/(4pi in_(0)r)=(4pi r^(2)sigma)/(4pi in_(0)r.)rArr (r^(2)sigma)/(in_(0)r)=(sigma)/(2in_(0))xx(1)/(100)`
since r = 1 cm and r. = 2cm
PD b/w the two points is equal to `(sigma)/(200 in_(0))`
work done `=VQ=(sigma)/(200 in_(0))X 2xx10^(-8)=11xx10^(-4)J`