D.C Series motor never operated on

D.C series motor both armature and feild connected in series at noload condition current drawn by the motor is zero Ia=0 flux also zero. but very small amount of flux avalible because of residual magnetism
in series motor speed  =  N α Eb/Φ Eb almost conistant

                                 =    N α 1/Φ

At no load condition d.c series can be run as dangerously very high so d.c series motor
operated at load condition only