motor effect

• what is a solenoid

  • coils of wire
• how to increase the strength of a magnetic field on a solenoid

  • add more coils
  • increase current
  • add an iron core - it becomes an induced magnet when the current flows through
• what is an electromagnet

  • a solenoid with an iron core
• what is the motor effect

  • occurs when a wire with a is placed in a magnetic field, experiences a force
• what are the two magnetic fields created in the motor effect

  1. Produced around the wire due to the current it is carrying
  2. Produced in the magnetic field where the wire is placed
• Factors affecting force in the motor effect

  • increased by increasising the current in the wire
  • Use stronger magnets
  • Place the wire 90 degrees to the direction of the magnetic field lines
• What is the left hand rule

  • Directon of force = thumb
  • direction of current = 2nd finger
  • direction of magnetic field = first finger
• what is a relay

  • allows a turn of the key to start the engine
  • contains a wound up solenoid around an iron core
  • when the car is turned on, a small current magnetises the solenoid
  • solenoid is attracted to the iron contacts
  • allows current to flow from the battery to the motor
• what is an electric motor

  • uses the motor effect to cause a force on the wire
  • can make a coil rotate
• how to form a DC motor

  • add a cell to form a complete circuit
  • coil is positioned in a uniform magnetic field
  • attatch coil to splirings+ carbon brushes
  • as the forces are in oppisite directions, the coil rotates
• how to change the speed of a dc coil

  • increase the current
  • use a stronger magnet
• how to change the direction of a dc motor coil

  • reverse the current
  • reverse the poles of the magnet
• how to change the force of a dc motor magnet

  • increase the current
  • add more turns
  • increase the strength of the mf
• how is a loudspeaker made

  • consists of a coil of wire wrapped around a permanent magnet
  • an ac passes through the coil which creates a magnetic field
• is a loudspeaker ac or dc

  AC - the current and magnetic field is always changing

  This is due to the mf of the coil interacting with the mf of the magnet which exserts an alternating force
• what is this force created

  oscillations