Electromagnitism

• Like poles repel, and unlike poles attract.
• The magnetic field lines of a bar magnet curve around from the north pole of the bar magnet to the south pole.
• Induced magnetism os magnetism created in an unmagnetised magnetic material when the material is placed in the magnetic field.
• Steel is used instead of iron to make permanent magnets because steel does not lose its magnetism easily but iron does.
• The magnetic field lines around a wire are circles centred on the wire in a plane perpendicular to the wire.
• The magnetic field lines in a solenoid are parallel to its axis and are all in the same direction. A uniform magnetic field is one in which the magnetic field lines are parallel.
• Increasing the current makes the magnetic field stronger. Reversing the direction of the current reverses the magnetic field lines.
• An electromagnet is a solenoid that has an iron core. It consists of an insulated wire wrapped around an iron bar.
• In the motor effect, the force is:

  • Increased id the current or the strength of the magnetic field or the length of the conductor is increased
  • Reversed if the direction of the current or the magnetic field is reversed.
• An electric motor has a coil that turns when a current is passed through it
• Magnetic flux density is a measure of the strength of a magnetic field.
• Force = Magnetic Flux Density x Current x Length
• Magnetic flux density is measured in Teslas (T)