MAGNETISM

• what is the poles of a magnet?


  the poles of a magnet are where the magnetic forces are the strongest
• two like poles


  repel
• two unlike poles


  attract
• what is a permanent magnet?


  produces its own magnetic field
• what is an induced magnet?


  object that becomes a magnet when it is placed in a magnetic field
• what force does an induced magnet cause?


  force of attraction
• give examples of magnetic materials


  iron nickel cobalt steel
• what is a magnetic field?


  the region around a magnet where a force acts on another magnet or on a magnetic material
• how does a compass show the direction of magnetic fields?


  it contains a bar magnet

  the north is attracted to the south so the compass needle points in the direction of the field it is in
• how to plot a magnetic field using a compass steps..


  • place a compass near the North Pole of the bar magnet
  • then draw a cross at the north pole of the compass
  • then move until the South Pole of the compass is on the cross
  • do this until a magnetic field is produced
  • then repeat north until magnetic field is formed
• how does earth have its own magnetic field


  due to its core
• how is a magnetic field produced in a wire


  when a current flows through a conducting wire a magnetic field is produced around the wire
• how can we prove there's a magnetic field


  • using a compass
  • when the current is turned off the compass needle lines p with the earths magnetic field however, if current turned on again the compass needle deflects
• how can we increase the strength of a magnetic field in an electromagnet

  increase the size of the current:

  larger current=stronger magnetic field

  adding more coils to form a solenoid: increases the strength of the field.
• how does adding a solenoid increase the strength of a magnetic field?

  the field lines around each loop of wire line up with each other this results in lots of field lines pointing in the same direction that are very close to each other. (closer=stroger)
• what is the magnetic field of a solenoid like


  strong and uniform
• what is an electromagnet?

  a solenoid with an iron core is called an electromagnet (the current can be turned on and off)
• what is the motor effect?


  when a current carrying wire is put between magnetic poles the magnetic field around the wire interacts with the magnetic field it has been placed in this causes the motor effect and causes the wire to move
• force=


  magnetic flux density x current x length
• what's the generator effect


  the generator effect induces a pd in a conductor in a wire which is experiencing a change in magnetic field
• what is a magnetic material

  can be influenced by magnetic fields
• the attraction between permanent and induced magnets are


  attraction
• a magnetic material that loses and gains magnetism quickly is

  a magnetically soft material
• a magnetic material that loses and gains magnetism slowly is

  a magnetically hard material
• why does shaping a wire to form a solenoid make the magnetic field stronger?

  because the field lines form/wrap a coil around each other resulting them to be close and pointing in the same direction

  closer=stroger
• whats an electromagnet


  a solenoid with an iron core
• how to increase the strength of an electromagnet

  increase the current through solenoid

  increase the number of coils (increases density)

  decrease the length of coils but keep the turns the same (decrease in length=quicker current)

  add a iron core
• how does adding an iron core increase the strength pf an electromagnet

  its a soft magnetic material meaning it can quickly lose and gain magnetism
• what's the motor effect

  when a current carrying wire is in the presence of a magnetic field it will experience a force
• to experience a full force the wire has to be

  perpendicular to the magnetic field
• if it experiences no force that means the wire is

  the same direction of the magnetic field
• whats the role of a split ring commutator

  ensures the current rotates in one direction and the forces are the same
• how does a spring ring work

  split ring swaps the positive and negative connections every half turn
• how to increase the number of rotations

  increase the current

  more coils

  increase magnetic flux density by adding more powerful magnets
• whats the generator effect

  if an electrical conductor moves relative to a magnetic field or if there is a change in magnetic field around a conductor a pd is induced
• if the wire is moving perpendicular to a magnetic field

  generate an alternating pd
• if the wire is moving parallel to th magnetic fie;d

  generate no pd
• how to change the size of the induced pd

  change the strength of magnetic field

  move wire or magnets more quickly

  shape wire into a coil
• whats a dynamo


  produces direct current and has a split ring commutator
• whats a alternator


  produces alternating current