In dc machines, 1. reactance voltage is proportional to armature current 2.reactance voltage is proportional to core length 3.reactance voltage is due to self-flux of the coil undergoing commutation 4. armature-cross flux is neutralized by interpolar flux 5. interpolarmmf is more than armature mmf in the interpolar zone From these, the correct answer is

• A.  1, 3, 5
• B.  1, 2, 3, 4
• C.  2, 3, 4
• D.  1, 2, 5

Answer: (D)