Induction, Electro-magnetic

The inter-reaction of electromagnetic lines of force with the production of currents thereby. A current pa ing through a conductor establishes around it a field of force representing a series of circular lines of force concentric with the axis of the conductor and perpendicular thereto. These lines of force have attributed to them, as a representative of their polarity, direction. This is of course purely conventional. If one is supposed to be looking at the end of a section of conductor, a uming a current be pa ing through it towards the observer, the lines of force will have a direction opposite to the motion of the hands of a watch. The idea of direction may be referred to a magnet. In it the lines of force are a umed to go from the north pole through the air or other surrounding dielectric to the south pole. Two parallel wires having currents pa ing through them in the same direction will attract each other. This is because the oppositely directed segments of lines of force between the conductors destroy each other, and the resultant of the two circles is an approximation to an ellipse. As lines of force tend to be as short as po ible the conductors tend to approach each other to make the ellipse become of as small area as po ible, in other words to become a circle. If on the other hand the currents in the conductors are in opposite directions the segments of the lines of force between them will have similar directions, will, as it were, crowd the intervening ether and the wires will be repelled. IMG:8956969607833025625_299F200.jpg: Fig. 200. ATTRACTION OF CONDUCTORS CARRYING SIMILAR CURRENTS. By Ampére's theory of magnetism, (see Magnetism, Ampére's Theory of,) a magnet is a umed to be encircled by currents moving in the direction opposite to that of the hands of a watch as the observer faces the north pole. A magnet near a wire tends to place the Ampérian currents parallel to the wire, and so that the portion of the Ampérian currents nearest thereto will correspond in direction with the current in the wire. 300   STANDARD ELECTRICAL DICTIONARY. This is the principle of the galvanometer. A number of methods of memoria technic a have been proposed to remember it by. Thus if we imagine a person swimming with the current and always facing the axis of the conductor, a magnetic needle held where the person is supposed to be will have its north pole deflected to the right hand of the person. IMG:8956969607833025625_300F201.jpg: Fig. 201. REPULSION OF CONDUCTORS