1. What is the effect produced by the electric current in an electric motor?
a) magnetic effect only.
b) magnetic as well as heating effect.
c) heating effect only.
d) heating as well as chemical effect.
ans. b
2. The rotating part of a d.c. motors is known as
a) pole
b) stator
c) armature
d) carbon brush.
ans. c
3. Why is the airgap between the yoke and armature of an electric motor kept smaller?
a) To achieve a stronger magnetic field.
b) To avoid overheating of the machine.
c) To make station easier.
d) None of these.
ans. a
4. The function of the commutator in a d.c. machine is
a) to change alternating current to direct current.
b) to improve commutation.
c) for easy speed control.
d) to change alternating voltage to direct voltage.
ans. d
5. Carbon brushes are used in electric motors to
a) brush off carbon deposits on the commutator.
b) provide a path for flow of current.
c) prevent overheating of armature windings.
d) prevent sparking during commutation.
ans. b
6. D.C. shunt generator has
a) slightly drooping characteristics.
b) appreciably rising characteristics.
c) constant voltage characteristics.
d) appreciably falling characteristics.
ans. a
7. which one of the following is used for charging batteries?
a) compound generator.
b) shunt generator.
c) series generator.
d) tacho generator.
ans. b
8. The speed of a d.c. motor is
a) directly proportional to back emf and inversely proportional to flux.
b) inversely proportional to back emf and directly proportional to flux.
c) directly proportional to emf as well as flux.
d) inversely proportional to emf as well as flux.
ans. a
9. In any d.c. generator the emf generated in the armature is maximum when
a) rate of change of flux linked is minimum.
b) rate of change of flux linked is maximum.
c) flux linked with conductor is maximum.
d) flux linked with conductor is minimum.
ans. b
10. The highest speed attained by a d.c. shunt motor is
a) equal to infinity at rated flux.
b) higher than no load speed at rated flux.
c) equal to no load speed at rated flux.
d) lower than no load speed at rated flux.
ans. c
a) magnetic effect only.
b) magnetic as well as heating effect.
c) heating effect only.
d) heating as well as chemical effect.
ans. b
2. The rotating part of a d.c. motors is known as
a) pole
b) stator
c) armature
d) carbon brush.
ans. c
3. Why is the airgap between the yoke and armature of an electric motor kept smaller?
a) To achieve a stronger magnetic field.
b) To avoid overheating of the machine.
c) To make station easier.
d) None of these.
ans. a
4. The function of the commutator in a d.c. machine is
a) to change alternating current to direct current.
b) to improve commutation.
c) for easy speed control.
d) to change alternating voltage to direct voltage.
ans. d
5. Carbon brushes are used in electric motors to
a) brush off carbon deposits on the commutator.
b) provide a path for flow of current.
c) prevent overheating of armature windings.
d) prevent sparking during commutation.
ans. b
6. D.C. shunt generator has
a) slightly drooping characteristics.
b) appreciably rising characteristics.
c) constant voltage characteristics.
d) appreciably falling characteristics.
ans. a
7. which one of the following is used for charging batteries?
a) compound generator.
b) shunt generator.
c) series generator.
d) tacho generator.
ans. b
8. The speed of a d.c. motor is
a) directly proportional to back emf and inversely proportional to flux.
b) inversely proportional to back emf and directly proportional to flux.
c) directly proportional to emf as well as flux.
d) inversely proportional to emf as well as flux.
ans. a
9. In any d.c. generator the emf generated in the armature is maximum when
a) rate of change of flux linked is minimum.
b) rate of change of flux linked is maximum.
c) flux linked with conductor is maximum.
d) flux linked with conductor is minimum.
ans. b
10. The highest speed attained by a d.c. shunt motor is
a) equal to infinity at rated flux.
b) higher than no load speed at rated flux.
c) equal to no load speed at rated flux.
d) lower than no load speed at rated flux.
ans. c
