Cyclopedia of applied electricity : a general reference work on direct-current generators and motors, storage batteries, electrochemistry, welding, electric wiring, meters, electric lighting, electric railways, power stations, switchboards, power transmission, alternating-current machinery, telegraphy, etc. (1916)
American Technical Society · Chicago : American Technical Society · leaf 211
ork, produced thereinminute changes of volume due to the variations of temperature; 183 2 WIRELESS TELEPHONY and such changes produced air-waves which were manifested inthe form of sound and audil)le within the tube. This simple device,invented by Alexander (iraham Bell, was called by him a… … THAfiJAT/TTEB Fig. 1. Bells Radiophone Selenium Cell. Li 1873, Willoughby Smith discovered thatthe resistance (jf metallic selenium was greatly reduced by exposureto light. The light from a small gas burner was found to exercisea marked influence on the conductivity of short rods of seleniumused as…
Electrical engineering
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