CLASSIFICATION AND NOTATION. xiii 



n speed in revolutions per minute or in revolutions per 

 second. This letter is frequently used where any 

 number of things, n, are to be represented in a 

 formula. 

 P power. 



/ number of field magnet poles of a dynamo. 

 The letter / is also used for power factor. 



/' number of current paths in an armature. 

 <J>, < magnetic flux. 

 <2, q quantity of electric charge. 

 R, r resistance. 



R a == armature resistance, R s = shunt field resist- 

 ance, R c = series field resistance. 

 $1 magnetic reluctance. 

 p specific resistance. 

 s area of a surface, sectional area. 

 vS stray power loss in a dynamo. 



t time ; also temperature. 

 T torque. 

 v linear velocity. 

 G> angular velocity. 

 W work. 

 X, x reactance. The letter x is also frequently used as a 



coordinate. 



Z, z impedance. The letter Z is also used for the number 

 of conductors on the surface of an armature, and for 

 the number of turns of wire in a coil. The letter z 

 is also used for the number of turns of wire per unit 

 length of a coil. 



= pZ/p'io B where Z is the number of conductors on the sur- 

 face of an armature. 



