MCQs on DC Machine

« Back         CONTENTS          Next »

1. The number of parallel path in a simplex lap winding is equal to
(a) number of poles
(b) number of pole pairs
(c) two
(d) two times number of pole      

 2. The number of parallel path in a simplex wave windings are equal to 
(a) two
(b) number of poles
(c) number of poles pairs
(d) no of coils 

 3. The number of parallel path in a 8-pole duplex wave winding is equal to
(a) 2
(b) 4
(c) 8
(d) 16 

 4. The number of parallel path in a 8-pole duplex lap winding is equal to
(a) 4
(b) 8
(c) 16
(d) 32 

 5. In DC machine, the fractional pitch winding is used to
(a) produce vibration
(b) reduce sparking
(c) avoid hunting
(d) avoid magnetic locking 

 6. In a DC machine, the sparking at the brushes is due to
(a) low contact resistance
(b) reactance voltage
(c) armature reaction
(d) over excitation 

 7. When the field excitation of a DC generator increases, its generated emf
(a) decreases
(b) increases
(c) remain same
(d) first increases then constant 

 8. The field coil of a DC machine are usually made of
(a) copper
(b) aluminium
(c) carbon
(d) mica    

  9. Then insulating material used between commutator segment is generally
(a) paper
(b) mica
(c) plastic
(d) fibre 

 10. The function of dummy coils in DC machines is to
(a) reduce armature reaction
(b) provide alternate flux
(c) reduce losses
(d) provide mechanical balancing    

  11. Permeability is reciprocal of  
(a) susceptibility
(b) reluctivity
(c) permittivity
(d) conductivity

 12. The purpose of using dummy coil in a DC machine is to
(a) reduce losses
(b) reduce armature reaction
(c) provide mechanical balance to armature
(d) improve power factor 

 13. The rotor part of a DC machine carries
(a) armature winding
(b) field winding
(c) either field or armature winding
(d) none of the above         

 14. If a field winding designed for series connection is connected in parallel, the machine will
(a) draw very high current
(b) stand still
(c) run normally
(d) run at slow speed            

 15. In the commutative compound machine, the mmf of the series field winding will ________ to the mmf of the shunt field winding.
(a) add
(b) minus
(c) same
(d) half     

 16. Which is the basic dominant factor in the production of the magnetic flux in a compound machine?
(a) Shunt field mmf
(b) Series field mmf
(c) Both shunt and series field mmf
(d) None of the above    

 17. The principle of dynamically induced emf is used in
(a) generator
(b) battery
(c) transformer
(d) all of the above     

 18. A dummy coil may required in a DC machine, if the machine is
(a) lap wound
(b) wave wound
(c) either lap or wave wound
(d) none of the above         

 19. In a DC Machine, the frog leg wound armature are designed for the use with
(a) high current high voltage
(b) high current low voltage
(c) moderate current and moderate voltage
(d) low current and low voltage 

 20. Which of the following is main factor to determine the size and rating of and electric machine?
(a) Current
(b) Temperature
(c) Speed
(d) Voltage 

« BACK                                        NEXT »

Leave a Reply

Your email address will not be published. Required fields are marked *