(H II IHT10N8 OP rXIFORM MOII..N -.il 



distance of / inches from the axis of rotation. The work 

 done in one revolution i- thru I-'TV/' inch-|ounds. IT tin- 

 conducting system makes H revolutions per second the 

 work done per second is '2-nrFn inch-pounds. Tin- i- 

 called the rate of working, being the work done in unit 

 time. We have then an expression for the rate of doing 

 work stated in terms of inch-in >u mis per second. Divide 

 this by 12 and we _'{ f.-.t-p. umls per second, divide 

 again by .V,u and we get the rate of working express. .1 in 

 hone-power, multiply by 7 Hi we get finally the same 

 quantity expressed in watts. If we now substitute t 

 the letter /, representing the torque in inch-pound-, 

 we get 



the rate of doing work r = o-7 1//, watt ...(10). 



This equation has been derived t'n.in purely nierli.-inir.il 

 considerations, anil does not necessarily involve nnythinir 

 electrical. 



\\ have already seen that-wln-n a <-urr.-nt of . .iniiteros 

 flows in a circuit a-t-d U|MUI by a magnetic system, tin- 

 t.-njii.- i- u'iveii by / lll-.W. \\hen- \l is the induct it.n 

 factor. If we insert this in place of / in Ivpiation 10 we 

 we that the rate of working is given by 



irsr.Vn=sr/> watts .. (II). 



where f is the tension induced by th* tn-.tion. \V- thus 

 arrive nf the very inijH.rtant rcttult that the rate of 



working ia -\pivn-ed by the product of the current 

 and the induced volts. 



ThiM < |iiation wot* derived by simply considering the 



forces acting on the conducting -\-t.-iu. and obtaining an 



*nion for the work done per *cond in term* of the 



