1. No of slip rings in D.C motor is:
(A) 3
(B) Zero
(C) 4
(D) 2
2. Brushes of D.C motor are made of:
(A) Hard carbon
(B) Soft carbon
(C) Carbon
(D) Aluminum
3. Armature reaction of an unsaturated D.C motor is:
(A) Cross magnetizing
(B) De magnetizing
(C) Magnetizing
(D) None of these
4. The back e.m.f in a D.C motor:
(A) Aids the applied voltage
(B) Opposes the applied voltage
(C) Aids the armature current
(D) None of these
5. The speed of D.C motor can be varied by varying:
(A) All of these
(B) Applied voltage
(C) Resistance in series with armature
(D) Field current
6. When the speed of D.C motor increases, its armature current:
(A) Increases
(B) Remains constant
(C) Decreases
(D) None of these
7. Types of D.C motor:
(A) Series
(B) Compound
(C) All of these
(D) Shunt
8. Motor runs backward, possible reasons:
(A) Low voltage
(B) Reverse connection
(C) Both a & b
(D) None of these
9. D.C motor heats up during running:
(A) All of these
(B) Short circuit
(C) Overload
(D) Bearing jam
10. The speed of D.C motor is:
(A) Always constant
(B) Directly proportional to the flux
(C) Directly proportional to back e.m.f
(D) None of these