D.C. Motor

• When a current-carrying coil is in a magnetic field, it experiences a turning effect.

  
• A DC motor runs on a direct current.

  
• The coil is made of insulated copper wire and is free to rotate between the poles of the magnet.

  
• The commutator (split-ring) is fixed to the coil and rotates with it.

  
• When the coil overshoots the vertical, the commutator changes direction of the current through it, so the forces change direction and keep the coil turning.

  
• The brushes are two contacts which rub against the commutator and keep the coil connected to battery, usually made of carbon

  
• The max. turning effect is when the coil is horizontal.

  
• There is no force when the coil is vertical, but it always overshoots this position

  
• The turning effect of a motor is increased by:

  • increasing the current
  • using a stronger magnet and increasing the strength of a magnetic field
  • increasing the number of turns on the coil
• Reversing rotation of a motor can be done by:

  • Reversing the battery
  • Reversing the poles