The Total solution for NCERT class 6-12
In a certain region ofspace, electric field is along the z-direction throughout. The magnitude ofelectric field is, however, not constant but increases uniformly along thepositive z-direction, at the rate of 105 NC−1 permetre. What are the force and torque experienced by a system having a totaldipole moment equal to 10−7 Cm in the negative z-direction?
Dipole moment of thesystem, p = q × dl = −10−7 Cm
Rate of increase ofelectric field per unit length,
Force (F)experienced by the system is given by the relation,
F = qE
= −10−7 ×10−5
= −10−2 N
The force is −10−2 Nin the negative z-direction i.e., opposite to the direction of electric field.Hence, the angle between electric field and dipole moment is 180°.
Torque (τ) is givenby the relation,
τ = pE sin180°
= 0
Therefore, the torqueexperienced by the system is zero.