Electromagnets - Physics

• Magnet

  • Has two poles, a north and a south pole
• North poles

  Attract south poles

  Repels north poles
• South poles

  Attract north poles

  Repels south poles
• Magnetic materials


  Will experience a magnetic force when placed near a magnet, this is a type of non-contact force as the materials do not have to touch for the force to be apparent
• Magnetic metals

  • Iron
  • Nickel
  • Cobalt
• Magnetic field

  An area where a magnetic material will experience a force
• Permanent magnet

  • Will have its own magnetic field
• Magnetic field lines

  Represent the field, these always travel out of the north pole of the magnet, and into the south pole
• Closer together the magnetic field lines are


  The stronger the magnetic field will be
• Finding the shape of a magnetic field

  1. Using plotting compasses

  2. Using iron filings
• Earth's magnetic field

  • Acts like a giant bar magnet inside the centre of the Earth
  • Allows compasses to work when navigating around the Earth
• Electric bell

  1. Electromagnet attracts the iron armature

  2. When it moves, it breaks the circuit, no longer allowing current to flow

  3. The coil and core are no longer magnetic meaning the spring is no longer attracted and returns to its original position

  4. The bell is rung once

  5. The circuit is complete again, restarting the process
• Circuit breaker

  • Detects large changes in current in a house, and will break a circuit
  • When a large current flows, the electromagnet becomes strong enough to attract an iron catch which will break a circuit
  • They can then be reset and used again
  • This makes them suitable as an electrical safety device in a home
• Loudspeaker

  A current passes through the coil and creates an electromagnet, this repels another permanent magnet which moves the cone in and out creating sound
• Electromagnet

  • Made by wrapping a coil of wire around a magnetic core
  • Only work when electricity is flowing through the coil, which means that they can be turned on and off
  • Stronger than permanent magnets
  • Produce the same magnetic field shape as a bar magnet
• Increasing the strength of an electromagnet

  • Increasing the number of turns on the coil around the core
  • Increasing the current which is flowing through the coil of wire
  • Using a more magnetic material for the core, e.g. iron rather than aluminium