Two charges respectively of `+3.2xx10^(-19)` coublem and `-3.2xx10^(-19)` coulomb are separated by a distance of `2.4xx10^(-10)`m . This dipole is placed in a homogeneous electric field of `4.0xx10^(5)V//m` . Find
(i) Electric dipole moment
(ii) The maximum moment exerted on the dipole by the electric field.
(iii) The energy necessary for rotating the dipole from equilibrium position to `180^(@)`.

Explanation

(i) The electric dipole moment
`P=qxx21`
`P=3.2xx10^(-19)xx2.4xx10^(-10)`
`P=7.68xx10^(-29)` coulomb `xx` meter
(ii) The moment of the couple acting on the dipole
`tau=pEsintheta`
for maximum moment `theta=90`
`tau=PE`
`=7.86xx10^(-29xx4.0xx10^(5)`
`=31.44xx10^(-24)`
`tau_("max")=3.14xx10^(-23)` newton `xx` meter
(iii) Potential energy of the dipole `U=-PEcos theta`. In the position of equilibrium `theta=0`
`thereforeU=-PE`
`U=-7.86xx10^(-29)xx4xx10^(5)`
`=-3.14xx10^(-23)J`
The energy Spent in rotating the dipole from `theta=0" to "theta=180^(@)`.
`W=U_(180)-U_(0)`
`=-PECos180-(-(PECos0)`
`=PE+PE`
`=2PE`
`=2xx7.86xx10^(-29)xx4xx10^(5)`
`=6.28xx10^(-23)J`