An Electric Current acts like a Magnet

Modern Electrical Inventions:
In order to understand the action of the electric bell, we must consider a third effect which an electric current can cause. Connect some cells as shown in Figure 200 and close the circuit through a stout heavy copper wire, dipping a portion of the wire into fine iron filings. A thick cluster of filings will adhere to the wire, and will continue to cling to it so long as the current flows. If the current is broken, the filings fall from the wire, and only so long as the current flows through the wire does the wire have power to attract iron filings. An electric current makes a wire equivalent to a magnet, giving it the power to attract iron filings.

Although such a straight current bearing wire attracts iron filings, its power of attraction is very small; but its magnetic strength can be increased by coiling as in Figure. Such an arrangement of wire is known as a helix or solenoid, and is capable of lifting or pulling larger and more numerous filings and even good-sized pieces of iron, such as tacks. Filings do not adhere to the sides of the helix, but they cling in clusters to the ends of the coil. This shows that the ends of the helix have magnetic power but not the sides.

If a soft iron nail or its equivalent is slipped within the coil, the lifting and attractive power of the coil is increased, and comparatively heavy weights can be lifted.

A coil of wire traversed by an electric current and containing a core of soft iron has the power of attracting and moving heavy iron objects; that is, it acts like a magnet. Such an arrangement is called an electromagnet. As soon as the current ceases to flow, the electromagnet loses its magnetic power and becomes merely iron and wire without magnetic attraction.

If many cells are used, the strength of the electromagnet is increased, and if the coil is wound closely, as in Figure, instead of loosely, as in Figure, the magnetic strength is still further increased. The strength of any electromagnet depends upon the number of coils wound on the iron core and upon the strength of the current which is sent through the coils.

To increase the strength of the electromagnet still further, the so-called horseshoe shape is used. In such an arrangement there is practically the strength of two separate electromagnets.

FIG. - A wire carrying current attracts iron filings.

FIG. - A loosely wound coil of wire.

FIG. - Coil and soft iron rod.

FIG. - An electromagnet.

FIG. - A horseshoe electromagnet is powerful enough to support heavy weights.