Electricity for public schools and colleges (1891)
Larden, W. (Walter), b. 1855 or 6 · London : Longmans · leaf 456
telephone. In this instrument no external source ofcurrent is needed, and it can act either as receiver or as transmitter. In the figure we have a section of the instrument; from thisthe construction can be explained. E is the mouthpiece into whichwe speak; M is a bar-magnet of about four inches… … the mouthpiece, the soft iron diaphragm vibrates in exact accordwith the air-waves impinging upon it. This acts inductively uponthe steel magnet, and alters the number of marked lines of forcepiercing the coil of fine long wire. This gives rise to inducedcurrents in the coil ; these will be feeble,…
Electricity
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