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How do earphones work?

  1. Apr 2, 2003 #1


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    I need help with my homework. We're supposed to explain how earphones work, using the simplest terms. I know it involves a coil of wire and a magnet and how the magnet vibrates with the sound but i can't quite explain it all myself. Any help would be appreciated.
  2. jcsd
  3. Apr 2, 2003 #2


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    Science Advisor

    Greetings !

    Welcome to PF c2 !

    (Oops... I thought you were asking about
    microphones so I started from one, I now
    added the earphone part below.)
    Well, in the simplest form like you asked, the
    magnet moves at the frequency of the sound waves
    and as it moves it creates an alternating
    magnetic field. This amf forces the free electrons
    in the coil to move back and forth as well which
    in turn creates an alternating electric field in
    the coil (and across the electric circuit), much
    like a generator.

    In an earphone, the same happens in reverse.
    An alternating electric field (at the appropriate
    frequency from a microphone or a recording) forces
    the electrons in the coil to move back and
    forth creating an amf round the coil. A magnet
    inside the coil (that has its own magnetic field)
    is affected by it and moves back and forth as well.
    As the magnet does so it creates sound waves of
    the required frequency in the air.

    Live long and prosper.
    Last edited: Apr 2, 2003
  4. Apr 2, 2003 #3


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    Staff: Mentor

    You just did explain it. Sound is a vibration. Coil makes the magnet (attached to the speaker) vibrate. Simple as that.
  5. Feb 5, 2007 #4
    Can you give me an appropriate MLA for this information?
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