P12 magnetism

• permanent magnets?


  produce their own magentic field and are always magnetic
• Four magentic materials: Iron, steel, cobalt, and nickel
• A compass is used to show the shape and direction of the field of a magnet.
• How can you use a plotting compass to determine the magnetic field of a magnet?

  Place a plotting compass on the paper and mark the direction of the field, move the compass to the end of the arrow you have draw, repeat and connect the field lines.
• Why does the Earth have a magnetic field?

  Because of the magnetic outer core
• Which hand do you need to use to work out the direction of the field around a straight conductor?

  RIght hand
• Which direction does current flow?

  Plus to minus
• What does the strength of the field around a long straight conductor depend on?

  Size of the current and distance from the conductor
• Describe the magnetic field inside a solenoid

  Very strong, almost uniform field
• Describe the magnetic field outside a solenoid

  Weaker 
• What will happen when a current carrying conductor is placed near a magnet?

  It will experience a force and an equal and opposite force will act on the magnet
• 4 ways to increase magnetic field strenght: 1)increase current 2)increase number of coils(keep length same) 3)decrease length (keep number of turns same) 4)add an iron core
• Electromagnets have a magnetic field that can be turned off and on by an electric current and can also be reversed by reversing the way current is flowing
• In flemmings left hand rule the current carrying wire has to be perpendicular to the magnetic field
• H: What are magnetic forces due to? interactions between magnetic fields
• What is Fleming's left-hand rule? Thumb = direction of the force, first finger = direction of magnetic field (N to S), second finger = direction of current (+ to -)
• What does the strength of a field around a long straight conductor depend on? the size of the current and the distance from the conductor
• What is a solenoid an example of? an electromagnet