electric motors

• a coil of wire carrying a current in a magnetic field tends to rotate and this is the basis of an electric motor
• the motor effect can be used to create a simple direct current electric motor, where the motor consists of a coil of wire which is free to rotate positioned in a uniform magnetic field
• • permanent magnets lie in fixed positions which creates a uniform magnetic field
  • a coil is positioned at 90 degrees to the direction of the magnetic field, and this current creates a magnetic field
  • the two magnetic fields interact and a force is exerted on the coil
  • current flows in opposite directions on each side of the coil, so the force will cause one of the sides to experience an upwards movement and the other side to experience a downwards movement
  • this causes the coil to rotate, however it can only rotate 180 degrees
• to allow the motor to turn 360:

  • a split ring commutator is used to allow the coil to rotate 360 degrees
  • the split ring commutator swaps the positive and negative contacts of the coil every half turn, and so it reverses the direction of the current every half turn meaning the forces acting on the coil are always acting in the same direction which means the coil will continue to rotate in the same direction
• to increase the speed of rotations in an electric motor you can:

  • increase the current
  • add more turns to the coil
  • increase the magnetic flux density by using stronger magnets