American telegraphy and encyclopedia of the telegraph; systems, apparatus, operation (1909)
Maver, William, jr. [from old catalog] · New York, Maver publishing company · leaf 143
force, in the vicinity of such a needle,may be considered as being of uniform direction and strength, and it only remains toinsure that the magnetic lines of the coil shall also be practically uniform in direc-tion in that portion of the field where the needle is placed, in ord.er to secure… … When wires conveying a current are i3laced parallel with each other, if the currentin each Avire is in opposite directions there is found to be repulsion between thelines of the respective wires, which may be represented as in Fig. 90. When thecurrent is in similar directions in the respective…
Telegraph
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