P4.5 How The Electric Motor Works

• What concept explains the force on a current-carrying wire in a magnetic field?

  The motor effect
• What determines the direction of the force on a wire in a magnetic field?

  The directions of the magnetic field and current
• How can we determine the direction of force on a wire?

  Using Fleming's left hand rule
• What happens to the force direction if the current direction is reversed?

  The force direction also reverses
• What happens when two wires are connected at one end in a coil setup?

  The coil will start to spin clockwise
• What occurs when the coil is rotated by 180 degrees?

  The current direction in the coil reverses
• What is the effect of reversing the current direction on the forces acting on the coil?

  The forces on each side of the coil swap direction
• What happens if the coil is left to rotate without current direction change?

  It will keep flipping back and forth
• What device is used to change the direction of current every half turn?

  A split ring commutator
• How does the split ring commutator affect the coil's rotation?

  It ensures the coil rotates in the same direction
• What happens when the positive terminal is connected to one side of the commutator?

  The current flows around the coil
• Why is the split ring commutator important in motors?

  It maintains consistent rotational direction
• What types of devices commonly use electric motors?

  Fans, vehicles, and hard drives
• How can we increase the speed of an electric motor's rotation?

  By increasing current, adding turns, or using stronger magnets
• What are the methods to increase the speed of an electric motor?

  • Increase the current passing through the wire
  • Add more turns to the coil
  • Increase the magnetic flux density with stronger magnets
• What does an electric motor do?


  Electric motor uses electricity to create a rotational motion. This is because a coil of wire carrying a current, placed in a magnetic field, rotates due to the motor effect.
• Split-ring commutator.

  
• How does a split ring commutator ensure the coil rotates in one direction?


  1. The split-ring commutator swaps the positive and negative connections every half-turn meaning the direction of the current through the coil reverses every half turn.
  2. This means that the forces acting on the coil will always be acting in the same direction.
  3. This causes the coil to rotate continuously and in one direction.
• Give 4 ways to increase the speed of rotation in an electric motor.


  1. Increase the current in the coil.
  2. Add more turns to the coil.
  3. Use stronger magnets.
  4. Add a soft iron core to the coil.