topic p7- magnetism and electromagnetism

• magnetic fields on a magnet

  
• • all magnets have a north and south pole
  • magnets create invisible field lines around them, as shown
  • when multiple magnets interact, they will either repulse or attract each other
  • 2 of the same poles repel, opposite attract
  • magnetic materials include iron, steel, nickel and cobalt
• the right-hand rule

  
• the right- hand rule

  • a magnetic field is created around a wire when a current flows through it
  • the field is made of concentric circle
  • point your right thumb in the direction of current in the wire, wrap your fingers up and this will show the direction of the wire field

  the field is stronger the closer you are to the wire
• solenoid

  
• solenoid

  • a wires magnetic field can be increased by wrapping it into a coil called a solenoid
  • the magnetic field produced by a solenoid is similar to a bar magnet, but it also has the field going through the coil
  • this field can be increased again by using an iron core inside the solenoid by becoming an induced magnet
  • if the current stops, the magnetic field also stops; this is know as an electromagnet
• the left-hand rule

  
• motor effect

  • the motor effect occurs when a wire magnetic field comes within two magnetic poles such as bar magnets
  • a force of attraction/ repulsion is created
• when a magnetic material is brought near a permanent magnet, it becomes an induced magnet
• compasses can be placed into a magnetic field and show the direction of the south pole
• the motor effect is used to create spinning motors by using dc currents and split ring commutators
• magnetic fields are shown stronger when field lines are closer together
• f=bil

  
• F=BIL

  force (newtons) = flux density (tesla) x current (amps) x length (meters)