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the 24th of November, 1885, it was 

 shown that the electromotive force in 

 volts of an ordinary dynamo is given by 

 the formula : 



« = nN 10 -6 (7), 



where z represents the total induction in 

 English lines of force (each equal to 

 6,000 C. G. S. lines), r the total number 

 of active wires counted all round the 

 armature, and N the speed in revolutions 

 per minute. If the machine is multi- 

 polar, and if the different armature-cir- 

 cuits are arranged in series, the expres- 

 sion for e must be multiplied by p, the 

 number of pairs of poles in the field. 

 Let k be the coefficient which expresses 

 the ratio between the electromotive 

 forces of the alternate and continuous- 

 current machines, then the formula for 

 the former is — 



e = kpzr^ 10~ 6 (8) 



if the total induction be given in English 

 lines of force. If in C. G. S. units the 

 electromotive force is — 



e = kpzT^- 10 -8 . 

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