motor effect

• What is the motor effect?

  A current carrying wire in a magnetic field experiences a force
• What happens when a current carrying wire is placed between two magnets?

  The wire experiences a force due to magnetic field interaction
• What angle must the wire be at to experience full force?

  The wire must be at exactly 90 degrees
• What happens if the wire is at a slight angle to the magnetic field?

  The wire will feel slightly less force
• What is the result if the wire runs in the same direction as the magnetic field?

  The wire will feel no force at all
• What two directions do we need to find the direction of the force?

  The direction of the magnetic field and the current
• What rule do we use to determine the direction of the force?

  Fleming's left-hand rule
• What does the first finger represent in Fleming's left-hand rule?

  The direction of the magnetic field
• What does the second finger represent in Fleming's left-hand rule?

  The direction of the current in the wire
• What does the thumb represent in Fleming's left-hand rule?

  The direction of the force felt by the wire
• What is the equation to calculate the strength of the force?

  f = b i l
• What does the variable 'f' represent in the equation?

  Force measured in newtons
• What does the variable 'b' represent in the equation?

  Magnetic flux density measured in teslas
• What does the variable 'i' represent in the equation?

  Current measured in amperes
• What does the variable 'l' represent in the equation?

  Length of the wire measured in meters
• -move a compass around the wire

  -changing direction of the compass needle shows a magnetic field is produced

  
• exam question

  • closing the (ignition) switch causes a current to pass through the electromagnet

  • the iron core (of the electromagnet) becomes magnetised

  • the electromagnet / iron core attracts the (short side of the ) iron arm

  •the iron arm pushes the (starter motor) contacts (inside the electromagnetic switch) together

  • the starter motor circuit is complete

  • a current flows through the starter motor (which then turns)

  
• -it moves or experiences a force horizontally to the right

  
• -increase current

  -increase magnetic field strength