. Electrical news and engineering . tJ CU^iyv^-y^C^t^^i^^ LxA. (yLtAAJi^ better form is adopted in practice. The simplest formmay be shown in diagram where A is a bar of iron, P isan insulated wire wound round and carrying an altern-ating current from the generator G, S being anotherinsulated wire also wound round .\ and P, (but insulatedfrom both) and leading to say the lamp L. On passingthe alternating current from G round A, the bar is atonce made an electromagnet, the poles of which reversetheir sign as the direction of the alternating currentreverses. The whole space surrounding A becomes
. Electrical news and engineering . tJ CU^iyv^-y^C^t^^i^^ LxA. (yLtAAJi^ better form is adopted in practice. The simplest formmay be shown in diagram where A is a bar of iron, P isan insulated wire wound round and carrying an altern-ating current from the generator G, S being anotherinsulated wire also wound round .\ and P, (but insulatedfrom both) and leading to say the lamp L. On passingthe alternating current from G round A, the bar is atonce made an electromagnet, the poles of which reversetheir sign as the direction of the alternating currentreverses. The whole space surrounding A becomes amagnetic field, the lines of force radiating in the manner ?^-^L. Diagram \I. indicated from one pole to the other. It is evident thatunder these conditions the coil S is just as much placedin a varying magnetic field as it was in diagram No. 5 ;hence a current will be induced in it. All transformersare built in this way : two coils wound together rounda magnetic circuit, and Insulated both from it and fromeach other, the one carrying the energizing currentcalled the primary, the other in which current is inducedcalled the secondary. The feature of special importancein this induction is that, no matter what may be thevoltage in the primary coil, we can get what voltage wedesire in the secondary, so that we can run our alter-nator at 1,000 or 2,000 or5,ooo volts, and still have only52, or 104, or any other desired voltage in our second-ary coils. This, of course, permits of the use of highvoltage for distribution and low voltage at lamps, ob-taining both economy and safety. The difference involtage between primary and secondary wires dependsdirectly
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