Two charges of `-9muC` and `+9muC` are placed at the points p(1,0,4) and Q(2,-1,5) located in an electric field `E=0.20hat(i)"V/m"`.
Calculate the torque acting on the dipole.

Explanation

As, `p(1,0,4)` and `Q(2,-1,5)`
`:." "2l="PQ"=[(2-1)hat(i)+(-1-0)hat(j)+(5-4)hat(k)]`
`=(hat(i)-hat(j)+hat(k))`
and `q=pm9xx10^(-6)" C,E"=0.20hat(i)"V/m",tau=?`
Since, `tau=pxxE=q(2l)xxE" "(becausep=qxx2l)`
`:." "tau=9xx10^(-6)(hat(i)-hat(j)+hat(k))xx0.20hat(i)`
`=18xx10^(-7)(hat(k)-hat(j))`
`:.` Magnitude of torque,
`tau=18xx10^(-7)[sqrt((1)^(2)+(1)^(2))]`
`=25.45xx10^(-7)"N-m"`