Elementary lessons in electricity and magnetism (1906)
Thompson, Silvanus P. (Silvanus Phillips), 1851-1916, Schwetzky, Otto H. L. [from old catalog] · Chicago, Thompson & Thomas · leaf 428
Single-Needle Instrument.—The single--needle instrument (Fig, 160) consists essentially of a vertical galvan-* ometer, in which a lightly hung magnetic needle is deflected to right or left when a current is sent, in one direction or the other, around a coil surrounding the needle; the needle… … CHAP. XII.] ELECTRICITY AND MAGNETISIM. 403 to send currents in either direction through the circuit.a signalling-key or tapper is usually employed.The tapper at one end of the line works the instru-ment at the other; but for the sake of convenience itis fixed to the receiving instrument. In Fig.…
Electricity · Magnetism
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