98 



ELECTRICAL ENGINEERING 



but only half of this flux surrounds each wire and therefore the 

 inductance of each wire per centimeter length is 



..s. units. 



(135) 



The flux inside the conductor has been neglected, but its in- 

 ductive effect can be calculated very easily if it is assumed that 

 the current is distributed uniformly over the section of the wire. 

 In Fig. 72 the section of wire A is shown enlarged. 



FIG. 72. Flux inside a conductor. 



The flux density at distance x cm. from the centre of A is 



9 l' 



OQ. " * 



a>$ = > 



X 



where 7' is the current inside the radius x cm. and its value is 



x z 

 T = 7 p- 2 c.g.s. units. 



The flux in the ring of radius x 9 width dx and length 1 cm. is 



, , 27' 2Ix , 



d<j> = dx = dx lines; 



this flux surrounds only the current 7' and is equivalent to a 

 smaller flux surrounding the current 7 of value 



