Magnetism and Electromagnetism

Magnetism and Electromagnetism

1. Magnetism

   • A uniform magnetic field is shown by straight lines
     • Uniform field line
     • Non uniform field line
   • Magnetic field line: An invisible line which shows direction of a magnetic field.
     • Always flow form NORTH to SOUTH
   • Rules: 1) Opposite Poles attract 2) Like poles repel 3) Field lined always flow from North to South
   • 3 magnetic metals: IRON, COBALT, NICKEL
   • Ferromagnetic metals (metals made out of iron) contains domains which are tiny crystals which have their own magnetic field.
     • When the metal is magnetised, these domains line up
     • Magnetically HARD materials: Domains are lined-up and fixed in place
       • Example: Steel
     • Magnetically SOFT materials: Domains are free to move and change direction
       • Can increase strength of field by stroking soft material with a magnet
       • Example: soft iron or pure iron

2. Electromagnetism

   • RIGHT HAND RULE FOR WIRES
     • Can be used to figure out the direction of the magnetic field
   • Perfect Electromagnet consists of: NICKEL, IRON COBALT (Core) and LOTS and LOTS of COILS
   • USES OF ELECTROMAGNETS: 1) Scrap yard crane, 2) MRI machines (magnetic resonance imaging, 3) The electric bell, 4) Circuit Breaker

3. Motor Effect

   • When a current carrying conductor, carrying an electric current is placed in the magnetic field, it will experience a force provided that the conductor (wire) is not placed parallel to the field lines.
     • The force increases if: the strength of the magnetic field is increased or the current is increased
     • The direction of the force is reversed if either: The direction of the current or the direction of the magnetic field is reversed
   • FLEMINGS LEFT HAND RULE!
     • NOTE: Magnetic field direction is NORTH TO SOUTH and Current direction is PLUS TO MINUS

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