Magnets

• All magnets have magnetic fields
• Using iron fillings to find a magnetic field:

  1. Put magnet under some paper
  2. Scatter some iron fillings on top
  3. The iron fillings will align themselves with the field
• Using a compass to find a magnetic field

  1. Put magnet on a piece of paper
  2. Place the compass next to the magnet
  3. Mark where the compass is pointing
  4. Move the compass in different locations on the paper and keep plotting the direction it faces
  5. Eventually, join up your points to create the field (beccase compasses always point North)
• Like poles repel
• Opposite poles attract
• Magnetic field lines always point towards the South pole

  (Out of N, into S)
• A current carrying wire has a magnetic field

  • Stronger the current = stronger the magnetic field
• The right hand rule

  1. Thumb is current
  2. Fingers are magnetic field

  
• A solenoid = When you have lots of coils of wire joined together

  
• The magnetic field inside a solenoid is strong and uniform

  
• To increase the magnetic field of a solenoid:

  • Increase the current
  • Increase the number of coils
  • Decrease the length of the solenoid
  • Add an iron core
• Motor effect = when a current carrying wire is placed in a magnetic field, it experiences a force

  
• Flemings Left Hand Rule

  Thumb = Force

  1st Finger = North pole

  2nd Finger = Current

  
• Force = magnetic flux density x current x length

  F = B x I x L

  (N) = (T) x (A) x (m)