Topic 7 - Magnetism and Electromagnetism

• What is a magnetic field?

  The region around a magnet where a force acts on another magnet or on a magnetic material
• what direction do magnetic field lines face?

  Out of North into South
• what metals are magnetic

  iron, nickel, cobalt
• what happens between two like poles?

  repulsion
• what happens between two opposite poles

  attraction
• What is an induced magnet?

  A material that becomes a magnet when it is placed in a magnetic field
• what is a permanent magnet?


  A magnet that produces its own magnetic field
• Magnetic materials that gain and lose magnetism slowly are called what?

  hard magnetic materials
• magnetic materials that gain and lose magnetism quickly are called what?

  soft magnetic materials
• What is a solenoid?

  A coil of current-carrying wire that produces a magnetic field
• how can you increase the force on a solenoid?

  increase current, number of coils, add iron core.
• What is Fleming's right hand rule?

  It gives the induced current direction by:

  1. Index finger points in the direction of the magnetic field.

  2. Middle finger points in the e.m.f. direction.

  3. Thumb shows the motion of the wire.

  
• What is the motor effect?


  A force experienced by a current-carrying wire in a magnetic field
• what direction must the wire be placed to a magnetic field in the motor effect?

  perpendicular
• what is Flemings left hand rule?

  Thumb - Force (movement)

  First finger - Magnetic Field

  Second finger - current

  
• what is magnetic flux density measured in?

  Tesla (T)
• how to increase the speed of rotation in an electric motor?

  increase current

  increase magnetic field / flux density

  add more turns to the coil.