The Motor Effect

• What is the effect experienced by a current-carrying conductor in a magnetic field?

  Motor effect
• What causes the motor effect?

  Interaction of current's field with magnetic field
• What factors can increase the force on a conductor in a magnetic field?

  • Increase the size of the current
  • Increase the length of the conductor
  • Increase the flux density
• What happens when the direction of the current or magnetic field is reversed?

  The direction of the force also reverses
• What can produce a large force in a conductor?

  Several cells producing a big current
• How can a large force be produced with stronger magnets?

  By giving a higher flux density
• What happens when the cell is reversed?

  The current and forces are reversed
• What occurs when the magnets are reversed?

  The magnetic field direction reverses
• How do you use Fleming’s left hand rule?

  1. Hold left hand with thumb, first, and second fingers at right angles
  2. Point first finger in the direction of the magnetic field (N to S)
  3. Point second finger along the wire in the direction of current
  4. Thumb points in the direction of the force
• What can Fleming’s left hand rule determine?

  The direction of field, current, or movement
• Electric Motors

  . A current carrying coil in a magnetic field will rotate

  . This is because the current going up one side of the coil is in the opposite direction to the current coming back down the other side, so one side moves up and the other moves down

  . This is the basis of an electric motor, which is designed so that the coil rotates continuously

  . The brush contacts at the commutator ensure that the current direction in the coil is always in the same direction

  . This ensures that the motor continues rotating and does not simply stop in the upright position

  . Fleming’s left hand rule can be used on one side of the coil to work out which direction the motor will rotate

  . Increasing the current or the magnetic field will make the motor rotate faster

  . Reversing the current or the magnetic field will make the motor rotate in the opposite direction
• Key Point

  The left hand rule can be remembered y:

  . First finger = Field

  . Second = Current

  . Thumb = Movement

  You must remember that the motor effect, it is the left hand rule
• Key Point

  The motor effect is used in motors to convert electrical energy into kinetic energy