Automobile-engine auxiliaries

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1910 edition. Excerpt: ...that is either smooth or grooved lengthwise. Such an armature is known as a drum armature. It is convenient to consider first the nature of the current generated in an elementary form of drum armature with a single closed coil, and then the method of causing the current from a similar coil to flow in only one direction through the portion of the circuit external to the armature. An elementary drum armature with a single closed coil is shown in Fig. 3 between the pole pieces a and b of the magnetic i 4r. field. The armature core c is cylindrical in form; the end view is shown. The straight parts d and e of the coil lie along the cylindrical surface of the _, drum and are perpendicular to the plane of the paper on which the figure is printed. When the drum is rotating counter-clockwise, as indicated by the feathered arrow just beneath it, and the coil is passing through the position shown, the straight parts d and e of the coil are cutting through the magnetic lines of force. This induces an electromotive force and causes an electric current to flow through the wire of the coil in the direction indicated by the two full arrows on the front of the coil and by the dotted arrow on the back end. The current flows in this direction during the time the part d is cutting through the lines from 1 to 2, and the part e from 3 to J,. The current flows through the front of the coil in the direction from the north pole to the south pole. While d is moving from 2 to 3 and e from 4 to /, no magnetic lines of force are cut; consequently, no current flows through the coil. As d continues to move from 8 to 4 it cuts through the same lines and in the same direction that e did before; at the same time e cuts through the lines previously cut by d and in the...