will prevent the nut from chafing the insulation on the wire ends.
Now connect the ends of the coil to the binding-posts of a battery cell, and you will be surprised to find what a strong magnet the head of the bolt core has become.
One end of the magnet coil should be connected to a dry-cell, and the other to a switch; and another wire should connect the switch with the dry-cell (Fig. 180).
A Home-Made Switch that is easily made is shown in Fig. 181. Cut strips A, B, and C (Fig. 182) from a tomato
Fig. 181.—A Home Made Switch.
Fig. 182.—Details of Switch.
can. Tack the turned up ends of A to a wooden knob (D). This forms the switch lever. Strips B and C, folded in half, and punched near the ends, form the binding-post plates.
Figures 181 and 182 show how to mount the lever and binding-post plates upon the switch base. Pivot lever A
