the motor effect

• the motor effect:

  • current creates magnetic field around coil
  • which interacts with permanent magnetic field
  • so, resultant force is produced
  • so wire moves
• loudspeaker:

  • current creates magnetif field around coil
  • which interacts with permanent magnetic field
  • producing force causing cone to move
  • when direction of current reverses, direction of force reverses
  • so, sound is produced
• converting current in electrical to sound wave:

  • current in electrical circuit varies
  • current passes through coil, so coil experiences force
  • reversing current reverses force, so coil vibrates
  • vibrating coil causes cone to vibrate
  • vibrating cone causes air molecules around cone to move
  • movement of air molecules causes produces pressure variations in air needed for sound wave
• electric motor:

  • sides of coil parallel to magnet experience force in opposite directions
  • forces cause moments that act in same direction
  • each half-turn, two halves of commutator swap from one brush to the other
  • so, each half turn, commutator reverses current in coil
  • so, coil keeps rotating