A charge of 8mC is located at the origin. Calculate the workdone in taking a small charge of `-2xx10^-9C` from a point P(0,03cm) to a point `Q(0,4 cm,0)` Via a point `R(0,6cm,9cm)`.

Explanation

From fig . A charge `q=8mc=8xx10^-3C` is located at the origin O. Charge to be carried is `q_(0)=-2xx10^-9` from P to Q
Where `OP =r_p=3cm`
`=3xx10^-2m` and
`OQ=r_Q=4cm=4xx10^-2m`
As electrostatic forces are conservative forces, workdone is independent of the path. Therefore , there is no relevance of point R.

`WP_(Q)=q_(0)=(V_Q-V_P)`
`WP_(Q)=(q q_0)/(4piepsi_0)((1)/(r_Q)-(1)/(r_P))`
`=9xx10^9xx8xx10^-3(-2xx10^-9)xx[(1)/(4xx10^-2)-(1)/(3xx10^-2)]`
`=-144xx10^-1xx10^2((-1)/(12))`
`=1,2` Joule.