Friday, December 14, 2007

Loudspeakers and Electromagnets

Science Homework

Research the use of electromagnets in a loudspeaker.



Loudspeaker

Diagram :
The loudspeakers in your radio, TV or stereo system use varying electric current through an electromagnet to create sound. The electric current varies at a fast rate, causing the strength of the magnetic field to vary. This results in moving the loudspeaker membrane or cone back and forth rapidly, resulting in sound and even music.
Take a look at a loudspeaker and see the coil of wire and electromagnet in its back area. Some loudspeakers use a solenoid instead of an electromagnet.

These first loudspeakers used electromagnets because large, powerful permanent magnets were not freely available at reasonable cost. The coil of the electromagnet is called a field coil and is energized by direct current through a second pair of terminals. This winding usually served a dual role, acting also as a choke coil filtering the power supply of the amplifier which the loudspeaker was connected to.

Sites Used :
http://www.school-for-champions.com/science/electromagnetic_devices.htm

http://en.wikipedia.org/wiki/Loudspeaker