A point charge of 9.6 `muC` is placed at a point A. Point B is at a distance of 10 cm from A. (i) Calculate electric potential at point B due to charge at A. (ii) If a point charge of 3 nC is brought from infinity to the point B, then calculate work done by the external agent in this process assuming motion of charge to be slow.

Explanation

(i) Given,
Charge located at point A, `q=9.6muC=9.6xx10^(-6)C`
Distance of point B from point A, `r=10cm=0.1m`
The electric potential at point B due to charge at point A is given by:
`V=(1)/(4pi epsilon_(0)) (q)/(r )`
`=9xx10^(9)xx(9.6xx10^(-6))/(0.1)`
`=86.4xx10^(4)V`
(ii) Electric potential at point B is equal to work done in bringing a unit positive charge from infinity to that point.
`therefore` Work done in bringing a charge of `q_(0)=3nC` from infinity to B will be
`W_(B)=q_(0)V`
`=3xx10^(-9)xx86.4xx10^(4)`
`=259.2xx10^(-5)J=26xx10^(-4)J`