E.M.F Equation of DC Generator

     We know that the working principle of dc generator, that when conductors begin to cut the magnetic lines of force and therefore, the e.m.f. induces in the conductors according to the Faraday's Law's of Electromagnetic Induction. The value of induced e.m.f. depends upon the lengths of the conductor, the magnetic field strength, and the speed at which the coil rotates. Let us see the equation for induced e.m.f.


   φ  = Flux per pole in Weber.

   Z  =  Total number of armature conductors.

   N  =  Armature rotation in revolution per minute ( r.p.m ).

   P = Number of poles.

   A  =  Number of parallel paths in armature.

   E  =  e.m.f induced in any parallel path or generated e.m.f.

      According to Faraday's law's of Electromagnetic induction.

Average e.m.f generated / conductors 

Flux cut / Conductors in one revolution,

dφ  =  φ P   wb

Number of revolutions / minute  

=  N / 60

Time taken for one revolution, 

dt  =  60 / N  sec

e.m.f generated / conductor 

Total e.m.f generated between the terminals

 E  =  average e.m.f generated per conductor  *  number of conductor in each parallel path


      A  =  P for lap winding

      A  =  2 for wave winding.

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