MAGNETISM & ELECTROMAGNETISM

MAGNETISM & ELECTROMAGNETISM

1. magnetic field

   • magnetic field line
     • size
     • Direction
     • North to South
       • Uniform field
         • straight
         • parallel
           • 2 permanent magnets near eachother
             • permanent magnet
               • retains magnetic properties in absence of magnetic field
     • investigate
       • Iron filings
         • magnet
         • paper
       • compasses
         • allign with field
   • region where magnetic materials experience a force
   • poles
     • LIKE
       • repel
     • OPPOSITE
       • attract
         • magnetic materials but non magnets
           • induced magnetism
             • material acts as magnet near magnet
     • close
       • dense
       • strong

2. electromagnetism

   • currnet carrying wire
     • magnetic field created
       • strength
         • size of current
         • Distance from wire
       • direction
         • right hand grip rule
       • around straight wire
         • concentric circles
       • around flat circular coil
         • concentric ellipses
       • around Solenoid
         • inside: strong + uniform
   • electromagnet structure
     • electromagnet = a soft metal core made into a magnet by the passage of electric current through a coil surrounding it.
     • soft
       • loses induced magnetism quickly
     • hard
       • keeps induced magnetism permanently
   • motor effect
     • current carrying wire is put between 2 magnetic poles
       • results in a force on charged particle as it moves
         • provided it's motion is no parallel to the field lines
           • wire needs to be at 90 degrees to receive full force
         • flemings left hand rule
         • appliance
           • D.C Motor
             • factors increase speed
               • more current
               • more turns on coil
               • Stronger magnetic field
               • soft iron core
             • 1) Coil on spindle
             • 2) Forces act ( 1 up, 1 down), Spindle rotates
             • 3) Split ring comutator swaps the contacts every half turn to keep the motor turning the same direction
             • factors change direction
               • swapping polarity of DC supply
               • sawpping polairty of magnetic poles
       • magnitude of force is dependent on
         • strength of magnetic field
         • amount of current
         • direction of current/magnetic field
   • electromagnetic induction
     • the creation of volatge (+current) in a wire which is experiencing a change in the magnetic field
     • Dynamo effect
       • coil of wire moves through magentic field
         • transforms kinetic energy into electrical energy
           • test by connecting ammeter
           • factors affecting voltage
             • strength of magnet
             • turns on coil
             • speed of movement
       • magnetic field moves through an electrical conductor

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