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PRACTICE / Magnetic torque on a loop

The magnetic moment follows the coil normal

A 40-turn plane coil has area 0.020 m² per turn and carries 0.50 A in a uniform 0.30 T magnetic field. Its plane makes 30° with the field.

What is the torque magnitude on the coil?

Organize the givens & assumptions
  • N = 40
  • A = 0.020 m²
  • I = 0.50 A
  • B = 0.30 T
  • Plane-to-field angle = 30°

Rigid thin turns, same enclosed area and current per turn, uniform external field; magnetic moment direction is the right-hand-rule normal to the coil plane.

  1. A0.12 N m0.12\ \mathrm{N\,m}
  2. B0.00153 N m0.0015\sqrt3\ \mathrm{N\,m}
  3. C0.063 N m0.06\sqrt3\ \mathrm{N\,m}
  4. D0.06 N m0.06\ \mathrm{N\,m}

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