Advanced Higher Physics

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					Advanced Higher Physics

  Inductors & Inductance
Magnetic Flux

    Magnetic flux, , is a measure of the magnetism in
     an area, given by –

     where -         -    magnetic flux (Wb)
                     B-    magnetic induction (T)
                     A–    area perpendicular to
                           magnetic field lines (m2)
Solenoids 1
  A coil carrying an
   electrical current is
   known as a solenoid.
  The current induces a
   magnetic field in the
  The direction of the
   field is determined by
   the direction of the
   current in the coil.
Induced EMF 1
    Any conductor contains ‘free electrons’

    When moving within a magnetic field
     individual electrons in a conductor experience
     a force, F = B I l sin, causing them to move

    This results in an induced EMF.

    Motion is relative – conductor in field or field
     past conductor.
Induced EMF 2


    Size of induced EMF relates to –

        Speed of motion
        Direction of motion
        No. of turns on coil

    EMF is caused by changing magnetic flux
Induced EMF 3
    Magnitude of EMF is related to rate of change of
     magnetic flux
                         e                (Faraday’s Law)
    If the magnetic field strength is changing, an EMF is
     induced in a conductor placed in the field.

    So an EMF can be induced by changing the strength
     of a magnetic field without needing to physically
     move a magnet or a conductor.
Uses of Magnetic Induction 1
    Video & audio cassette
     players, hard drives are
     magnetic media.

    Information is recorded
     onto a magnetic tape or
     disc, which passes a coil
     with an iron core (reading
     head), inducing a current.

    The current provides the
     signal required for the
Uses of Magnetic Induction 2
  Electric guitars use steel
   strings and magnetic pick-
  As the strings vibrate, the
   magnetic field of the pick-
   up changes
  A coil wrapped around the
   magnet has a current
   induced, producing a signal
  The signal is amplified and
   sent to a loudspeaker
Uses of Magnetic Induction 3
  Microphones have a
   diaphragm connected
   to a coil which moves
   within a magnetic field
  Sound wave cause
   the diaphragm and
   coil to vibrate inside
   the magnetic field,
   inducing a current.
  The signal is
   amplified and sent to
   a loudspeaker.

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