The principles underlying radio communication (1922)
United States. National Bureau of Standards, Ould, Richard Sheldon, 1889-, United States. Army. Signal Corps · Washington, Govt. Print. Off. · leaf 112
key A: is open, the induced current cannot flow. If it is closed, an induced current does flow, andsets up a magnetic field about the coil. It can be shown thatmore work is required^-to move the magnet with respect to thecoil when the key is closed than when it is open. These factsare expressed in… … I
Telegraph, Wireless · Radio
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