An electric dipole consists of two opposite charges each 0.05 $\mu$C separated by 30 mm. The dipole is
placed in an uniform external electric field of 10⁶ NC^-1. The maximum torque exerted by the field
on the dipole is 

Given,   $q=0.05\mu \mathrm{C}=5\times {10}^{-8}\mathrm{C}$

2a = 30  mm = 0..0.3 m and E = 10⁶ NC^-1

Torque acting on an electric dipole placed in an uniform electric field,

$\tau =pE\sin \theta$

For maximum torque, $\theta$ = 90⁰

$\therefore {\tau }_{\max }=pE=E(q\times 2a)$

$={10}^6\times 5\times {10}^{-8}\times 0.03$

$=1.5\times {10}^{-3} \mathrm{N}-\mathrm{m}$