CHAPTER XI.
INDUCTION COILS AND THEIR ATTACHMENTS.
134. Induction Coils, or shocking coils, are rather expensive to buy, and altogether too complicated for boys to make by the methods usually given in books. The method here given is simple, the materials are cheap, and if you make them according to directions, you will have an apparatus that will, be able to make your friends dance to a rather lively tune. The amount of shock can be regulated perfectly ([App. 103]).
Winding. Full instructions have been given for making bolt magnets ([App. 88]). The winding of our induction coils is done in the same way by the same winder as the bolt magnets ([App. 93]), or by hand. You will find it a very tiresome and troublesome job, however, to wind on 12 or 15 hundred turns of fine wire by hand. Make a winder.
Several different forms of induction coils are shown. The coil is the most important feature, however, and we shall consider that separately. When you understand the construction of one coil, you can readily apply this to the different forms. Some form of contact breaker, or current interrupter, is needed also. These will be treated by themselves. The connections will be discussed under each form of apparatus.
135. Induction Coil; Construction of Coil Proper. Figs. 73, 74. An induction coil is a peculiar and wonderful apparatus. There are at least two coils to each one. These are both wound upon the same core. They are made of different sizes of wire, are wound separately, and the strangest thing of all is, that these two coils are not connected with each other in any way. If they were not thoroughly insulated from each other, the coil would be of no value. (Study induction.) The winding of the two coils is done as explained in [App. 88].
| Fig. 73. | Fig. 74. |
136. The Core is made of a 5⁄16 machine bolt, 2½ in. long. Leave but 2 or 3 threads at the end, just enough to fasten it solidly to the winder ([App. 93]). The washers should be about 1⅝ in. apart inside, and they should be made around a spool ([§ 119]) that is fully 1 in. in diameter.
137. The Inside or Primary Coil could be wound directly upon the bolt; but it is much better to cover the bolt with one or two thicknesses of paraffined paper, I (Index), as shown. A pinhole, H, in the washer is for the inside end ([see § 123]) of the primary coil, and the hole, J, is for the outside end of it.