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Class 12
Physics
Electric Charges and Field
in a certain region of space electric field is al...

Question:
In a certain region of space, electric field is along the z-direction throughout. The magnitude of electric field is, however, not constant but increases uniformly along the positive z-direction, at the rate of 10⁵ NC^-1per metre. What are the force and torque experienced by a system having a total dipole moment equal to 10^-7 Cm in the negative z-direction?

Answer:

Dipole moment of the system, p = q × dl = - 10 ^{- 7} C m

Rate of increase of electric 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}N in 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 (Ãâ€ž) is given by the relation,

Ãâ€ž = pE sin180°

= 0

Therefore, the torque experienced by the system is zero.

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