permanent and induced magnets

• the poles of a magnet are where the magnetic forces are the strongest
• permanent magnets have their own magnetic fields
• incuded magnets become a magnet placed in a magnetic field
• the arrows run from north to south
• flux density is how close the lines are in the magnetic field which indicated strength
• when a current flows through a conducting wire a magnetic field is produced
• the direction of the line can be found with the right hand grip method
• the strength of the field depends on

  • the size of the current
  • the distance from the wire
• solenoid

  • a wire is looped into a cylindrical coil
  • this increases the strength of the magnetic field
  • it creates a strong uniform field
• magnetic field of a solenoid

  
• electromagnets

  • an iron core is added to a solenoid
• a solenoid increases magnetic field

  • concentrating a long piece of wire into a small area
  • the looped shape means that the magnetic field lines around the wire are all in the same direction
• use the right hand grip methode

  • direction of the current
  • north pole of a solenoid
• electromagnetic devices (doorbell)

  
  

  1. when the switch is pushed, the electromagnet is magnetised
  2. the electromagnet attracts the armature
  3. the hammer strikes the gong and breaks the circuit
  4. the armature springs back , completing the circuit again and remagnetising the electromagnet
  5. the cycle repeats as long as the button is being pushed