MAGNETIC EFFECT OF ELECTRIC CURRENT. 



97 



Fig. 62. This side force is at right angles to the wire and to the 

 magnetic field (Fig. 48) which is acting on the wire. The side 

 force which acts upon the wire in Fig. 6 1 may be ascribed to the 

 tension of the lines of force. 



Examples. The simple example of the magnetic effect of the 

 electric current which is cited in Art. I and represented in Fig. I 

 illustrates the side push of a magnetic field on a wire inasmuch 

 as the magnetic field which emanates from the north pole of the 

 magnet in Fig. I is partly, at least, at right angles to the wire 

 AB. The side push on an electric wire in a magnetic field is also 

 exemplified in the electric motor. A cylindrical mass of iron A, 

 Fig. 63, has wires arranged on its surface parallel to its axis, and 



>X" o^- f?. 



; jpX0 



<r 



Fig. 63. 



the whole is placed between two magnet poles NS, as shown. 

 The narrow region between the cylinder A and the poles N and 

 5 is a strong magnetic field, the lines of force of which are radial. 

 An electric current is made to flow through the wires in the direc- 

 tions indicated by the dots and crosses, and the result is that the 



visible agent which is acting on the wire. It is very important, however, that the 

 student become familial with the idea of a magnetic field as a physical reality, and to 

 ascribe the side force in Figs 6 1 and 62 to the field which is produced by the two mag- 

 net poles puts the whole matter in the most intelligible form. 



