Consider the diagram below (sorry for the quality). The circle is the front view of a cylindrical iron rotor (highly ferromagnetic, very low reluctance). The orange part is a single turn of a conductor (very high reluctance) wound around the rotor body. The grey lines are magnetic field lines from external magnetic poles, which you can see are crowded in the ferromagnetic iron body. The number of lines actually cutting the conductor is negligible compared to the those in the iron body because of very high reluctance of the conductor. (This is similar to what happens in a practical dc machine.) Now, keeping the magnetic field stationary, if the rotor is rotated through 90°, there will be a "change of flux" associated with the conductor loop. This should induce an emf in the loop as per Faraday's law E=dΦ/dt. But since the conductor is actually cutting a negligible number of magnetic field lines, the motional emf should be almost zero. What am I missing? Please help..