magnets

• like poles repel
• opposite poles attract
• magnetic forces are non contact forces magnets do not have to be touching to be pulled together
• not all metals are magnetic:

  magnetic metals are:

  iron - fe

  cobalt - co

  nickel - ni
• steel is often magnetic however steel is a mixture of metals called an alloy. it contains iron
• magnets exert forces within their magnetic fields
• field lines must be drawn with an arrow pointing north to south
• if the magnetic fields are strongest at either the north or south poles the field lines will be closer together
• the earth has a magnetic field this is because the earths core contains iron
• • The magnetic field around the Earth is able to deflect ionising radiation from space.
  • We can see this deflection as the Aurora Borealis or the Northern Lights.
  • It is thought that birds, turtles and whales all use the Earth's magnetic field for navigation.
  • We also use this magnetic field for navigation when we use a compass.
• • Electromagnets can be found in:
  • Television sets.
  • Maglev trains.
  • MRI machines.
  • Loudspeakers.
  • Scrapyard cranes that are able to pick up and move vehicles.
  • Electric bells.
• • If an electrical item moves, chances are it has an electric motor.
  • A motor is a coil of wire between two magnets.
  • When the wire is placed between the magnets in their magnetic field it moves.
  • This is called the motor effect.
• This is a DC motor. Electric current flows when the sides hit and pushes the magnet to revolve. This is the basis of all moving electronics.

  
• difference between a solenoid and electromagnet:

  An electromagnet is an electrically induced magnet surrounded by a coil of wire through which an electric current is passed to magnetise the core.

   A solenoid is a cylindrical coil of wire acting as a magnet when carrying an electric current.
• magnetic field strength for a coil of wire (solenoid) :

  • For a solenoid (coil of wire), the magnetic field inside the solenoid is strong and uniform.
  • Outside of the solenoid the magnetic field decreases in strength the further away it is from the solenoid. 
  • Increasing the size of the current increases the strength of the magnetic field produced by a solenoid.