Advanced Higher Physics

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Advanced Higher Physics

• Electromagnetic Induction

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Magnetic Flux

• Magnetic flux, ?, is a measure of the magnetism
  in an area, given by
• ? B A
• where - ? - magnetic flux (Wb)
• B - magnetic induction (T)
• A area perpendicular to magnetic
  field lines (m2)

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Solenoids 1

• A coil carrying an electrical current is known as
  a solenoid.
• The current induces a magnetic field in the coil
• The direction of the field is determined by the
  direction of the current in the coil.

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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.

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Induced EMF 2

• SCHOLAR DEMO
• Size of induced EMF relates to
• Speed of motion
• Direction of motion
• No. of turns on coil
• EMF is caused by changing magnetic flux

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Induced EMF 3

• Magnitude of EMF is related to rate of change of
  magnetic flux
• (Faradays 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.

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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
  system

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Uses of Magnetic Induction 2

• Electric guitars use steel strings and magnetic
  pick-ups
• 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

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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.