Magnetism and electromagnetism

• The poles of a magnet are the places where the magnetic forces are strongest
• When two magnets are brought close together they exert a force on each other
• Two like poles repel each other. Two unlike poles attract each other
• Attraction and repulsion between two magnetic poles are examples of non-contact force
• A permanent magnet produces its own magnetic field.
• An induced magnet is a material that becomes a magnet when it is placed in a magnetic field.
• Induced magnetism always causes a force of attraction
• When removed from the magnetic field an induced magnet loses its magnetism quickly.
• The region around a magnet where a force acts on another magnet or on a magnetic material is called the magnetic field.
• The strength of the magnetic field depends on the distance from the magnet. The field is strongest at the poles of the magnet.
• The direction of a magnetic field line is from the north pole of a magnet to the south pole of the magnet.
• A magnetic compass contains a small bar magnet
• The Earth has a magnetic field.
• The compass needle points in the direction of the Earth’s magnetic field.
• When a current flows through a conducting wire a magnetic field is produced around the wire.
• The strength of the magnetic field through a conducting wire depends on the current through the wire and the distance from the wire.
• Shaping a wire to form a solenoid increases the strength of the magnetic field created by a current through the wire
• A solenoid  consists of a wire coiled up into a spiral shape
• The magnetic field inside a solenoid is strong and uniform.
• The magnetic field around a solenoid has a similar shape to that of a bar magnet.
• Adding an iron core increases the strength of the magnetic field of a solenoid
• An electromagnet is a solenoid with an iron core.
• The motor effect:

  When a conductor carrying a current is placed in a magnetic field the magnet producing the field and the conductor exert a force on each other
• factors affecting the force on a conductor:

  • current
  • length
  • magnetic flux density
• A coil of wire carrying a current in a magnetic field tends to rotate. This is the basis of an electric motor