GCSE Physics (AQA)

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Coil in a Magnetic Field

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Magnetism and electromagnetism The motor effect

Coil in a Magnetic Field

5:54 The Motor Effect
Spec 4.7.2.3
Previous Fleming's Left-Hand Rule Next Electric Motors
  • A rectangular coil rotates when carrying a current in a uniform magnetic field due to the motor effect.
  • The motor effect occurs when a current-carrying wire experiences a force in a perpendicular magnetic field.
  • Demonstration setup: Rectangular coil placed between two magnets with a magnetic field between them.
  • An electric current is sent into the coil, causing it to experience a force and rotate.
  • Coils wrapped around themselves multiple times can also demonstrate this effect.
  • Sections of the coil parallel to the field lines do not experience a force.
  • Only conductors perpendicular to a magnetic field experience a force.
  • Opposing forces on the left and right sides of the coil cause it to rotate.
  • Fleming's left-hand rule helps determine the direction of forces on the coil.
  • Forces cause the coil to rotate counterclockwise initially.
  • The coil rotates around a pivot due to opposing forces at either end.
  • Momentum from initial forces allows the coil to continue rotating.
  • Direction of current changes as the coil flips, altering the rotation direction.
  • The coil can only complete half turns with this setup, flipping back and forth.
  • There is a method to allow full rotation in one direction, but it is not covered here.
  • Understanding the rotation and half-turn limitation is important for exams.

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