Speaker

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Introduction:
A speaker is a device that converts an electronic signal into sound. The speaker you will build (see figure 1) consists of a Styrofoam or paper cup, a coil of wire, a permanent magnet, and a signal source. The electronic signal goes through the coil and creates a varying electromagnet. The attraction and repulsion between the electromagnet and the permanent magnet cause the cup to vibrate and produce sound.

Activity:
Materials:
 * 1 permanent magnet
 * 2 feet of wire
 * sandpaper
 * 1 pencil
 * tape
 * 1 Plastic cup
 * 1 signal source
 * 1 plug for tape player

Assemble materials as shown in figure 1.


 * 1) Leaving about 5 centimeters on each end, wrap the wire around a pencil to make a wire coil. The coil should be about 1 centimeter in diameter and contain about 50 coils.
 * 2) Scrape the insulation off 1-2 centimeters of the ends of the coil.
 * 3) Tape the coil to the bottom of the plastic cup.
 * 4) Place the cup on the magnet base and tape to wooden dowel.
 * 5) Secure the coil ends to the two wing nuts and attach the ends of the plug (must make contact to complete the circuit.
 * 6) Attach your device.
 * 7) Adjust the apparatus until you get sound coming out of your speaker.

Conclusion:

 * 1) Does the volume control on the tape player work on your speaker? Explain your answer.
 * 2) What kind of sound quality do you get out of your speaker? Compare the loudness and the clarity.
 * 3) How does the sound quality compare with your normal speakers/earbuds?
 * 4) Explain how your speaker reproduces sound.
 * 5) Explain what happens when you place a coil of wire near a permanent magnet.