Jump to content

Page:Home-Made Toys for Boys and Girls (Hall).djvu/149

From Wikisource
This page has been proofread, but needs to be validated.
HOME-MADE ELECTRICAL TOYS
119

An electro-magnet consists of a center core of soft iron, wrapped with a coil of insulated wire. When an electric current passes over a wire, a magnetic field is formed around the wire; and when several turns of insulated wire are wrapped about a soft iron core, the magnetic fields of all the turns of the coil, or helix, combine, forming a very strong magnetic field which strongly magnetizes the iron core. As I have said before, this magnet loses its magnetic influence the instant the current ceases to pass through the surrounding coil of wire.

Figs. 177-179.—The Electro-Magnet.
Figs. 177-179.—The Electro-Magnet.

Figs. 177-179.—The Electro-Magnet.

You will need a machine-bolt or carriage-bolt 2½ or 3 inches long, and ¼ inch in diameter, for the core of the magnet, some insulated electric-bell wire for the coil, and a piece of heavy cardboard. Cut three washers of a trifle larger diameter than the bolt-head, out of the piece of cardboard (Fig. 178), and slip these over the bolt as shown