IV.  Distribution  of  Magnetic  Flux 

43.  The  distribution  of  magnetic  flux  in  the  air  gap  or  at  the 
armature  surface  can  be  calculated  approximately  by  assuming 
the  density  at  any  point  of  the  armature  surface  as  proportional 
to  the  m.m.f.  acting  thereon,  and  inversely  proportional  to  the 
nearest  distance  from  a  field  pole.  Thus,  if  FQ  =  ampere-turns