CHAPTER XVI.
ELECTRO-MAGNETIC MACHINES.
The experiments already described in illustration of some of the phenomena of electro-magnetism are of such a simple nature that they may be comprehended without difficulty; but it is not such an easy task to appreciate the curious fact of an invisible power producing motion. It has already been explained that a copper or other metallic wire conveying a current of electricity becomes for the time endowed with a magnetic power, and if held above, or below, or close to, a suspended magnetized steel needle, affects it in a very marked degree, causing it to move to the right or left, according to the direction of the electric current; and in order to form some notion of the condition of a metallic wire whilst the electricity is passing through it, the annexed diagrams may be referred to. (Figs. 201, 202.)
Fig. 201.
Portion of a square copper conductor, in which a b represents the direction of the electricity, and the small arrows, c c c c, the magnetic current or whirl at right angles to the electrical current, and exercising a tangential action.
Fig. 202.
A round conducting wire, in which the electrical current is flowing in the direction of the large dart a b, and the small arrows indicate the direction of the magnetic force.