The Motor Effect

• what is produced when a current flows through a conducting wire

  magnetic field produced around wire
• what does strength of magnetic field depend on

  current through the wire and distance from the wire
• what increases strength of magnetic field (created by current through wire)

  shaping the wire to form a solenoid - magnetic field inside a solenoid is strong and uniform
• what does adding an iron core do to the strength of magnetic field of a solenoid

  increases strength - magnetic field around a solenoid has a similar shape to a bar magnet
• what is an electromagnet

  solenoid with an iron core
• what is the motor effect

  when a conductor carrying a current is placed in a magnetic field, the magnet producing the field and the conductor exert a force on each other
• what does Fleming's left hand rule represent

  relative orientation of the force, the current in the conductor and the magnetic field
• equation for force (for a conductor at right angles to a magnetic field and carrying a current)

  magnetic flux density x current x length

  F = B x I x 1

  N = T x A x m

  (newtons = Tesla x amps x metres)
• what is the basis of an electric motor

  a coil of wire carrying a current in a magnetic field tends to rotate
• how do loudspeakers and headphones use the motor effect

  to convert variations in current in electrical circuits to the pressure variations in sound waves