Question

An electric dipole of length 4cm, when placed with its axis making an angle 60o with a uniform electric field, experiences a torque of 4 root 3 Nm. Calculate the

(i) magnitude of the electric field

(ii) potential energy of the dipole, if the dipole has chages + or - 8nC

Answer 1

Dipole moment (P) = q.2l

$$\begin{gathered} P=8\times {10}^{-9}\times 2\times 4\times {10}^{-2} \\ P=64\times {10}^{-11}Cm \end{gathered}$$

Torque on the dipole in Uniform field is:

$$\begin{gathered} \tau =PE\sin \theta \\ E\hspace{0.17em}=\frac{\tau }{P\sin \theta } \\ Potentialenergyofthedipoleis: \\ U=-PE\cos \theta \end{gathered}$$

On substituting the value we can find out the value of E and U.