MCQOPTIONS

Explore topic-wise MCQs in Dc Machines.

This section includes 12 Mcqs, each offering curated multiple-choice questions to sharpen your Dc Machines knowledge and support exam preparation. Choose a topic below to get started.

1.	Each of the following statements regarding interpoles is true except______________________
A.	They are small yoke-fixed poles spaced in between the main poles
B.	They are connected in parallel with the armature so that they carry part of the armature current
C.	Their polarity, in the case of generators is the same as that of the main pole ahead
D.	They automatically neutralize not only reactance voltage but cross-magnetisation as well
Answer» C. Their polarity, in the case of generators is the same as that of the main pole ahead

2.	The most likely cause(s) of sparking at the brushes in a DC machine is /are ____________
A.	Open coil in the armature
B.	Defective interpoles
C.	Incorrect brush spring pressure
D.	Open coil in armature, defective interpoles and incorrect brush spring pressure
Answer» E.

3.	Why dummy coils are connected in DC machine?
A.	To reduce eddy current losses
B.	To enhance flux density
C.	To amplify voltage
D.	To provide mechanical balance for the rotor
Answer» E.

4.	Function of interpole flux is_________
A.	Neutralise the commutating self-induced emf
B.	Neutralise the armature reaction flux
C.	Neutralise both the armature reaction flux as well as commutating emf induced in the coil
D.	Perform none of the above functions
Answer» D. Perform none of the above functions

5.	Exact purpose of compensating winding in a DC generator is _________
A.	Mainly to reduce the eddy currents by providing local short-circuits
B.	To provide path for the circulation of cooling air
C.	To neutralise the cross-magnetising effect of the armature reaction
D.	Cannot be determined
Answer» D. Cannot be determined

6.	What is the exact location of compensating winding?
A.	Across armature
B.	In series with armature
C.	Across armature or in series
D.	Cannot be determined
Answer» C. Across armature or in series

7.	Which of the following method will completely neutralize the armature reaction in a DC machine?
A.	Only compensating winding
B.	Only interpoles
C.	Compensating winding and interpoles
D.	Cannot be determined
Answer» D. Cannot be determined

8.	Inequality in brush arm currents caused due to different emf induced in different parallel paths may give rise to copper losses. These effects can be avoided by using _________
A.	Compensating windings
B.	Interpoles
C.	Equalizer rings
D.	Cannot be determined
Answer» D. Cannot be determined

9.	Where are no equalizer rings connected?
A.	Only wave winding
B.	Only lap winding
C.	Both wave winding and lap winding
D.	Cannot be determined
Answer» B. Only lap winding

10.	What is the ampere turns per pole for compensating winding in DC machines?
A.	(pole arc / pole pitch) * armature ampere turns per pole
B.	(pole pitch / pole arc) * armature ampere turns per pole
C.	* armature ampere turns per polec) (pole arc / pole pitch) * total ampere conductors per pole
D.	Cannot be determined
Answer» B. (pole pitch / pole arc) * armature ampere turns per pole

11.	In order to neutralize armature mmf perfectly under the pole shoe, the ampere-conductors of compensating winding must be (pole arc/pole pitch=1) _______
A.	Not equal to the total armature ampere conductors under the pole shoe
B.	Equal to the total armature ampere conductors under the pole shoe
C.	Half of the total armature ampere conductors under the pole shoe
D.	Twice of the total armature ampere conductors under the pole shoe
Answer» C. Half of the total armature ampere conductors under the pole shoe

12.	The armature reaction in a DC machine causes distortion in the main field flux. Effect of armature reaction can be reduced by_________
A.	Increasing the length of air gap
B.	Decreasing the length of air gap
C.	Increasing the number of poles
D.	Decreasing the number of poles
Answer» C. Increasing the number of poles