Lessons in practical electricity; principles, experiments, and arithmetical problems, an elementary text-book . duction coil is to transform the energydelivered to its primary from any given voltage to a higheror lower voltage. While a current of low pressure may thusbe transformed into one of a very high pressure, the latterloses in current what it gains in pressure, so that the watts in the secondaryare no greaterthan those de-veloped in theprimary, but al-ways a little less,owing to variouslosses in trans-formation andthe C square Rloss in the sec-ondary circuit. 301. The In-duction Coil.—T
Lessons in practical electricity; principles, experiments, and arithmetical problems, an elementary text-book . duction coil is to transform the energydelivered to its primary from any given voltage to a higheror lower voltage. While a current of low pressure may thusbe transformed into one of a very high pressure, the latterloses in current what it gains in pressure, so that the watts in the secondaryare no greaterthan those de-veloped in theprimary, but al-ways a little less,owing to variouslosses in trans-formation andthe C square Rloss in the sec-ondary circuit. 301. The In-duction Coil.—The principle ofthe transformer is utilized in induction coils constructed togenerate very high electromotive forces, capable of overcomingthe resistance of the air and causing sparks to pass across airgaps. The induction coil, or Rhumkorffs inductorium, , is a step-up-transformer since, by induction, it raises thevoltage of several cells connected to its primary to thousandsof volts at the secondary terminals. It consists of a straightlaminated core, made up of a bundle of soft charcoal iron wires. IS Fig. 284.—Induction or Spark use with direct currents. THE INDUCTION COIL. 317 around which is wound the cylindrical primary coil, com-posed of several layers of heavy wire, while a secondary coilcomposed of thousands of turns of fine wire, is wound overthe primary, similar to Fig. 283. The inner or primary coilis connected to a battery through an automatic interrupter,Fig. 285. At the make and the break of the primarycircuit currents areinduced in the sec-ondary according tothe laws of induc-tion, % 284, andappear as a seriesof sparks passingthrough the air fromone secondary ter-minal to the general appear-ance of such a coilis shown in , and its connec-tions, in Fig. 285, Exp. 87 : The students induction coil illustrated in Fig. 266, maybe mounted on a base provided with a contact screw and vibratorarm, when induced currents can be produced a
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