Lessons in practical electricity; principles, experiments, and arithmetical problems, an elementary text-book . y the number of turns upon it by the strength of currentpassing through it. For example : four amperes circulating 25 times arounda coil produce a magnetising force of 100 ampere-turns. Thesame force could be produced by 2 amperes and 50 turns,or 100 amperes and 1 turn, or 100 turns and 1 ampere, or1000 turns and one-tenth ampere, etc., the product of theturns and current in each case being 100. Let C = current in amperes ;T = number of turns. Then, Magnetising Force = C X T (54). Al
Lessons in practical electricity; principles, experiments, and arithmetical problems, an elementary text-book . y the number of turns upon it by the strength of currentpassing through it. For example : four amperes circulating 25 times arounda coil produce a magnetising force of 100 ampere-turns. Thesame force could be produced by 2 amperes and 50 turns,or 100 amperes and 1 turn, or 100 turns and 1 ampere, or1000 turns and one-tenth ampere, etc., the product of theturns and current in each case being 100. Let C = current in amperes ;T = number of turns. Then, Magnetising Force = C X T (54). AlgoC = MagaefeingJWe (55) T Magnetising Force (56). 198. Reluctance.—The magnetising force or magnetomotiveforce, as it is called, is the force set up by the ampere-turns,which drives the magnetic lines, or magnetic flux, through themagnetic circuit, just as an electromotive force causes a currentof electricity to flow through an electric circuit. A magneticcircuit offers a resistance, called reluctance, to the magneticlines, and this reluctance must be overcome by the magnetis- 194 PRACTICAL Fig. 185.—The Dotted CentreLine Represents the MeanLength of the Mag-netic Circuit. Induction ing force before induction is invoked. The number or densityof lines of force per square inch of the circuit is called theinduction per square inch and corresponds with the currentin an electric circuit. It depends upon the magnetisingforce and reluctance. The length ofthe magnetic circuit in Fig. 185 isshown by the dotted line. The re-luctance of all non-magnetic bodies ispractically the same, and when anysuch are interposed in a magnetic cir-cuit the number of lines of force isgreatly diminished. In magnetic cal-culations the magnetising force of thecircuit is divided by the magneticreluctance of the circuit to obtainthe magnetic density, and by adopt-ing units for the terms force, reluct-ance, and density, calculations are made similar to thoseused in an electric circuit, but a
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