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Question: Answered & Verified by Expert

Two charges of each magnitude 0.01 C and separated by a distance of 0.4 mm constitute an electric dipole. If the dipole is placed in an uniform electric field E of 10 dyne·C-1 making 30 angle with E, the magnitude of torque acting on dipole is:

PhysicsElectrostaticsJEE MainJEE Main 2023 (13 Apr Shift 1)
Options:
  • A 4.0×10-10 N m
  • B 1.0×10-8 N m
  • C 1.5×10-9 N m
  • D 2.0×10-10 N m
Solution:
1011 Upvotes Verified Answer
The correct answer is: 2.0×10-10 N m

The formula to calculate the dipole moment is given by

p=qd   ...1

Substitute the values of the known parameters into equation (1) to calculate the dipole moment.

p=0.01 C×0.4 mm×1 m103 mm= 4.0×10-6 C·m

The formula to calculate the torque on the dipole in the electric field is given by

|τ|=|p×E|   ...2

Substitute the values of the known parameters into equation (2) to calculate the required torque.

τ= 4.0×10-6 C·m×10 dyne·C-1× 1 N105 dyne×sin30°= 2×10-10 N m

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