electric motors

• what is a split ring commutator?

  reverses current direction every half turn
• why does a coil in an electric motor rotate when there is a current in the motor?

  • there is a magnetic field due to the permanent magnet
  • current in the wire causes a magnetic field
  • the two magnetic fields interact
  • current is in opposite directions in each side of the coil so forces act in opposite directions on either side of the coil
  • split ring commutator reverses the current every half turn
• how does the generator induce a direct current in a coil?

  • coil moves through the magnetic field
  • a potential difference is induced
  • there is a complete circuit, so a current is induced
  • every half-revolution the commutator switches brushes
  • so the direction of the induced current doen't reverse every half rotation