an electric dipole is placed at an angle 60^{0 }with an electric field of strength 4×10^{5 }N/C. it experiences a torque equal to 8\sqrt3 Nm. calculate the charge on the dipole, if dipoleis of length 4cm (1) 10^{-1 }C (2)10^{-2} C (3)10^{-3 }C (4) 10^{-4}