NEW ZEALAND TARANAKI

A Musical Motor

Build your own speaker, which is really a special kind of electric motor!


Build a motor that moves forward and back instead of round and round...

A simple speaker:

  • Wind 500 turns of enamelled copper wire around a cut-down Fuji film cannister.
  • Sit an ice-cream container on top that has a circular magnet glued on the back.
  • Attached to the two free ends of the coper wire a headphone jack plug.
  • Using the headphone jack, plug your speaker into a CD player or iPod (or other sound source). Listen to the music!

You can use tin cans instead of the ice-cream container and you don't even need the magnet!

Speakers make use of the motor effect.

A wire that has an electric current flowing through it, like our 500 turns of copper wire, becomes a magnet (an electromagnet). If near a permanent magnet, like the one glued onto the ice-cream container, it will be attract or repulse it, depending on which poles are close together.

This means the bottom of the container with the magnet glued on will move back-and-forth with the magnet, slapping into the air, creating sound waves.

Our walkman supplies the electric current, but it turns the electromagnet on and off very fast to creating a linear (back-and-forth) movement rather than a rotational one (like inside normal motors). The linear motion of the our speaker "cone" creates air pressure waves that we perceive as sound.


FIND OUT MORE:-

  1. Try and find out about subwoofers, tweeters and other speakers you can buy from shops. How are they different from your speaker?
  2. Learn more about motors; build a motor here....
  3. What did Michael Faraday discover?
 

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