Torque required to hold a small circular coil of 10 turns, 2 × 10 - 4   m 2 area and carrying 0 .…

Torque required to hold a small circular coil of 10 turns, 2×10-4 m2 area and carrying 0.5 A current is the middle of a long solenoid of 103 turns per meter carrying 3 A current, with its axis perpendicular to the axis of the solenoid is
  1. 12π×10-7 N m
  2. 6π×10-7 N m
  3. 4π×10-7 N m
  4. 2π×10-7 N m

Solution

Dipole moment of the coil, M=NAI=10×2×10-4×0.5

⇒M=10-3 A m2

Magnetic field due to solenoid, B=μ0nI=4π×10-7×103×3

⇒B=μ0nI=12π×10-4 T

Torque =MBsinθ=12π×10-4×10-3

Torque =12π×10-7 N m

Asked in: AP EAMCET 2021 (20 Aug Shift 2)

Practice more Magnetic Fields due to Electric Current questions on Aicharya