A dc shunt generator, when driven without any excitation, showed an open circuit voltage of 12 V. When the field winding was excited, the voltage dropped to zero. It happened because

• A.  there was no residual magnetism in the field circuit
• B.  there was a break in the armature circuit
• C.  field resistance was higher than critical resistance
• D.  field winding was wrongly connected

Answer: (D)