permanent and induced

• what metals are magnetic

  • iron
  • steel
  • cobalt
• what is a magnetic field

  • area around the magnet
  • gets weaker as you increase distance from poles
• how is the force dependant on the magnetic field

  • if the mf is weak, the force is small
  • if the mf is strong, the force is large
• how does a compass work

  • contains a small bar magnet which rotates
  • when at rest, the compass points in the north to south direction which proves that the earth has a magnetic field
• what is a permanent magnet

  • produces its own magnetic field
  • always have a north and south pole
• what is an induced magnet

  • temporary
  • becomes magnetic when placed in a magnetic field
  • always attracted to permantent magnets due to the induced magnet being magnetised to the mf
  • ie soft iron
• what domains are in unmagnetised iron

  • all in different/random directions
  • adding electricity shakes up the domains
• what domains look like in magnetised iron

  • in the same direction
• what is magnetic flux

  • represented by the lines drawn in the direction of force on a north pole
  • more/less lines = stronger/weaker flux density
• how to determine flux density

  • dependant on the strength of magnetic force
• what is the right hand rule

  • thumb is up or down - points in the direction of the current
  • fingers point in the direction of the field
• O

  = current is flowing out of the page
• X

  = current flows into the page
• what is the law of magnetism

  • when two magnets are held close together, there will be an attractive or repulsive force between the magnets
  • like - repel
  • different - attract \
• what is the force of a magnet in a magnetic field

  attraction
• where is the MF strongest

  • closest to the magnet ie at rhe poles
  • weaker as you move further away
• how do you plot the magnetic field using a compass

  • go from north to south
  • field lines never touch

  1. place magnet on paper
  2. draw dot on one end of the magnet
  3. place a compass next to the dot so that one end of the compass points away from the dot
  4. use a pencil to draw a new dot at the other side
  5. move compass so it points away from new dot
  6. repeast until there is a chain of dots going across the magnet
• how do we know that the earth is magnetic

  • the geographic south pole attracts a compass north pole