By connecting one of the coils, A, with the battery by means of the
wires, the action of a helix or solenoid is shown. When so connected,
the helix will draw up with itself a barrel pen, or any light iron or
steel object. (See Fig. 4.) This is not a true solenoid, but it is
generally known by that name. In a true solenoid one of the terminals
is passed back through the center of the coil.

[Illustration: FIG. 4.--SOLENOID.]


MAGNETIZATION OF STEEL.

By inserting in the solenoid a knitting needle, or any bar of hardened
or tempered steel, and sending a current through the coil, the steel
will become permanently magnetized.


ELECTROMAGNET.

By placing the two coils, A, upon the magnet frame, B, and connecting
one terminal of each with the battery, the remaining terminals being
connected together, as shown in Fig. 5, an electromagnet is formed
which will lift several pounds.

[Illustration: FIG. 5.--ELECTROMAGNET.]


ELECTRIC MOTOR.