School of Physics Lecture Demonstration Manual

Ej-3 Loud-speaker

Published: Tuesday 05 June 2007 - Updated: Tuesday 29 March 2011


To demonstrate the principles of a loudspeaker



Click on pictures to enlarge.

Loudspeaker pic 1

Loudspeaker pic 2


A wire coil of about 100 turns is tightly wound on a cardboard tube former. This is attached to a cardboard cone which will act as our diaphragm. The output of a small radio receiver is used to drive a PA amplifier, a light globe is used in series with the coil to act as a suitable load. When a strong magnet is brought close to the coil a reasonable rendition of the radio signal ensues.

Safety notes

Electrical Safety 


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