electromagnetic induction

• • EM induction used to generate electricity
  • when voltage is induced in a conductor or a coil when it moves through a magnetic field / when a magnetic field changes through it
  • This is done by by conductor or coil cutting thru the magnetic field lines
  • aka generator effect, opposite to motor effect

  1. motor: there is already a current in the conductor which experiences a force
  2. generator: there is no initial current in the conductor but one is induced (created) when it moves through a magnetic field
• GENERATING A PD

  • A potential difference will be induced in the conductor if there is relative movement between the conductor and the magnetic field
  • Moving the electrical conductor in a fixed magnetic field when a conductor(eg wire) is moved through a magnetic field, the wire cuts through the fields lines: induces a pd in the wire

  A) wire

  B) conductor

  C) potential difference

  
• • Moving the magnetic field relative to a fixed conductor: As magnet moved through the coil, the field lines cut through the turns on the coil -> induce pd in coil
  • A sensitive voltmeter can be used to measure the size ofthe induced potential difference
  • If the conductor is part of a complete circuit then a current is induced in the conductor

  
• PD FACTORS

  • size

  1. speed which wire / coil / magnet is moved (rate that magnetic field lines are cut)
  2. no of turns on coils of wire (each coil will cut thru the magnetic field lines and the total potential difference induced will be the result of all of the coils cutting the magnetic field lines)
  3. size of coils (area: more wire to cut through the magnetic field lines)
  4. strength of magnetic field

  • direction

  1. orientation of magnetic poles, Reversing the direction in which the wire, coil or magnet is moved
• definition: when we have relative motion between a coil and a magnetic field, an electric current or electromotive force (emf) is induced in the coil