P4.2

• when does the motor effect occur?

  when a wire with current flowing through it, is placed in a magnetic field and experiences a force

  • this force is the result of 2 interacting magnetic fields
  • one is produced around the wire due to the current flowing through it
  • the second is the magnetic field into which the wire was placed e.g. between two magnets
• how can we increase the size of the force exerted by the magnetic fields?

  1. increase the current --> will increase the magnetic field around the wire
  2. use stronger magnets --> will increase the magnetic field between the poles of the magnet
  3. placing the wire at right angles to the direction of the magnetic field lines --> maximum interaction between 2 magnetic fields
• what happens if the magnetic fields are parallel?

  there is no interaction between the 2 magnetic fields and therefore no force produced
• what can the motor effect be used to create?

  a simple direct current electric motor
• how does an electric motor work?

  current creates a magnetic field around the coil

  • this interacts with the field produced by the magnets
  • a force is exerted on the coil

  as the current flows in opposite directions on each side of the coil, the force will push one side of the coil up and the other side down
• what happens in an electric motor once the coil is in a vertical position?

  there will be a force acting upwards and a force acting downwards.

  using a split ring commutator, the direction of the flow of current reverses

  • as a result, the coil continues to rotate
• how do you keep the coil rotating continuously in an electric motor?

  the commutator reverses the direction of the current in the coil every half turn
• what is electromagnetic induction used for?

  to generate electricity