When an electric dipole of moment `| vec(p) | = q xx 2a` is held at an angle `theta`, with the direction of uniform external electric field `vec(E)`, a torque `tau = pE sin theta` acts on the dipole. This torque tries to align the electric dipole in the direction of the field. When `vec(p)` is along `vec(E), theta^(@) , tau = pE sin 0^(@) = zero`. The dipole is in stabel equilibrium. The energy possessed by the dipole by virtue of its particular position in the electric field is called potential energy of dipole. `U = W = -pE (cos theta_(2) - cos theta_(1))` `theta_(1) = 90^(@)` is the position of zero potential energy. ` :. U = W = -pE (cos theta - cos 90^(@)) = -pE cos theta`. For stable equillibrium, `theta 0^(@), :. U = -pE` = minimum. Read the above passage and answer the following questions : (i) What is the direction of torque acting on electric dipole held at an angle with uniform external electric field ? (ii) An electric dipole of length 10cm having charges `+- 6xx10^(-3) C`, placed at `30^(@)` with respect to a uniform electric field experiences a torque of magnitude `6 sqrt(3) N-m`. Calculate. (a) magnitude of electric field. (b) potential energy of dipole. (iii) What is the physical significance of this concept in our day to day life ?