50 



ELECTRICAL ENGINEERING 



In Fig. 40 (a) represents a uniform magnetic field between two 

 unlike poles and (6) represents the field surrounding a conductor 

 carrying current. If the conductor is placed in the uniform field 

 the resultant distribution will be as shown in (c). The intensity 



(a) W ^ f 



FIG. 40. Force on an electric conductor in a magnetic field. 



of the field above the conductor will be greater than that below 

 and a force / will act on the conductor at right angles to it and to 

 the lines of flux, tending to push it out of the field. This force is 

 directly proportional to the intensity of the field or the flux den- 



FIG. 41. Force exerted by a magnetic field on a coil of wire. 



sity, to the length of the conductor in the field and to the strength 

 of the current, or 



/ = Z&ll dynes, (80) 



where 3 is the flux density in lines per square centimeter, 

 I is the length of the conductor in centimeters, 

 I is the strength of the current in absolute units. 



