Magnetism and Electromagnetism

• Poles of a magnet

  The parts of a magnet where the magnetic forces are the strongest
• What happens when two magnets are brought close to each other

  They exert a force on each other
• Type of force exerted when two like poles of a magnet are brought together

  A repulsive, non-contact force
• Type of force exerted when two opposite poles of a magnet are brought together

  An attractive, non-contact force
• Permanent magnet


  Produces its own magnetic field
• Induced magnet


  a material that becomes a magnet when it is placed in a

  magnetic field.
• Induced magnetism always causes a force of

  attraction.
• When an induced magnet is removed from a magnetic field it..?

  -it loses most/all of its magnetism
• Magnetic field


  • The region around a magnet where a force acts on another magnet or on a magnetic material
• Magnetic materials


  • Iron
  • Steel
  • Cobalt
  • Nickel
• The force between a magnet and a magnetic material is always attractive
• Moving further away from the magnet producing the magnetic field makes..?

  The magnetic field strength decrease
• Direction of a magnetic field

  • given by the direction of the force that would act on another north pole placed at that point.
  • The direction of a magnetic field line is from the north (seeking) pole of a magnet to the south(seeking) pole of the magnet.
• Magnetic compass


  • Contains a small bar magnet that points in the direction of the Earth's magnetic field
• What is produced when current flows through a conducting wire?


  • A magnetic field is produced around the wire
• Factors which affect the strength of a magnetic field around a current- carrying wire?

  • The magnitude of the current flowing through the wire
  • The distance from away the wire
• Solenoid



  • A coil of wire which when current passes through creates a strong magnetic field
• Type of Magnetic field inside a solenoid

  • Strong and uniform
• Electromagnet


  • A solenoid with an added iron core
  • Adding the iron core increases the strength of the magnetic field
• Motor effect



  • When a conductor carrying a current is placed in a magnetic field , the mafnet producing the field and the conductor exert a force on each other
• Flemings Left-Hand rule


  Used to determine the force experienced due to the motor effect
• How Flemings Left Hand rule represents force + current

  • Forefinger points in the direction of the magnetic field
  • Second finger points in the direction of the current flow in the conductor
• The force on a given length of wire in a magnetic field increases when:

  • the current of the wire increases
  • the strength of the magnetic field increases
  • the length of the conductor in the field is increased
• If the direction of current in a current-carrying wire placed in a uniform magnetic field is reversed



  • The direction of the force is reversed
• What is magnetic flux density measured in

  Tesla,T
• For a conductor at right angles to a magnetic field and carrying a

  current: Force =

  Force = magnetic flux density × current × length

  (N) (Tesla,T) (Amps,A) (m)
• How an electric motor works

  • A coil of wire, carrying a current, is placed in a magnetic field
  • The forces on the two sides perpendicular to the field experience forces in opposite directions
  • This causes a rotational effect