Davis's manual of magnetism : including galvanism, magnetism, electro-magnetism, electro-dynamics, magneto-electricity, and thermo-electricity . eutralizing action described in <§» 409and <§) 411, is due to a secondary current excited in theinterposed metallic plate or spiral, which itself in-duces a tertiary current in the wire coil, flowing inan opposite direction to the secondary induced in itby the battery current, and therefore retarding itsdevelopment. A tertiary current is also induced inthe battery coil, which occasions the reduction in thespark and shock noticed in 393 and 411.
Davis's manual of magnetism : including galvanism, magnetism, electro-magnetism, electro-dynamics, magneto-electricity, and thermo-electricity . eutralizing action described in <§» 409and <§) 411, is due to a secondary current excited in theinterposed metallic plate or spiral, which itself in-duces a tertiary current in the wire coil, flowing inan opposite direction to the secondary induced in itby the battery current, and therefore retarding itsdevelopment. A tertiary current is also induced inthe battery coil, which occasions the reduction in thespark and shock noticed in 393 and 411. Whenthe interposed plate of metal is divided to its centre,no secondary is induced in it, and it exerts no neu-tralizing action ; the same is the case with the ribbonspiral in <^ 411, when its cups are phenomena are produced by the introductionof a metallic tube into a wire helix, as describedin <§.403. 416. This tertiary Qixmni can be separated from TERTIARY CURRENTS. 259 the secondary, and obtained by itself, in the followingmanner. A ribbon coil B (Fig. 170) being laid upon Fig. the coil A, through which the battery current istransmitted, connect its cups with those of a thirdspiral, C, of the same kind, removed to a little dis-tance, so as to be beyond the influence of the cur-rent in A. The secondary current induced in B willnow flow through C, and if a fine wire coil, W, is laidon C, strong shocks may be obtained. If W is raisedup, the shocks are still felt when it is at a consider-able height above C. 417. By placing a fourth ribbon coil on C insteadof the wire coil, a quantity current will be obtained,capable of aflTecting the galvanometer slightly, andof magnetizing a sewing needle placed in a helix ofsmall i/ternal diameter. Let two fine wire coils besubstituted for the flat spirals B and C. A secondaryintensity current will now be obtained, which willinduce a tertiary of intensity in a third wire coil laidon the second, enabling i
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Keywords: ., bookcentury1800, bookdecade1850, booksubjectmagnetism, bookyear18
