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0 Electrical Machines Multiple Choice Questions on “Operating Characteristics of DC Generators
1. Which of the following characteristics reveal about the magnetization nature of the machine?
A. No-load characteristics
B. Load characteristics
C. Armature characteristics
D. Both no-load and load characteristics
Answer: D
Clarification: Both no-load and load characteristics are required to predict the magnetization of the machine.
2. Choose the most inappropriate out of the following for the no-load characteristics of the dc generator.
A. It is the open circuit characteristic of the machine
B. It is magnetization characteristic of the machine
C. It is conducted on the unloaded machine
D. None of the mentioned
Answer: D
Clarification: All the mentioned nature of the characteristics are correct.
3. The external characteristic is plotted between ____________
A. terminal voltage vs armature current at constant excitation
B. terminal voltage vs field current at constant armature current
C. induced armature emf vs armature current at constant excitation
D. none of the mentioned
Answer: A
Clarification: The external characteristic is plotted between terminal voltage and armature current at fixed excitation.
4. A student forgot to mark the x-y axes in his experiments but he just noted down the cause and the effect for each. How will he conclude about the armature characteristic out of the all plotted graphs?
A. By marking graph for constant terminal voltage
B. By marking graph for constant field current
C. By marking graph for constant armature current
D. By marking graph for constant speed
Answer: A
Clarification: Armature characteristic is observed at constant terminal voltage for emf vs armature current.
5. Armature characteristic is also known as _________
A. regulation characteristic
B. magnetization characteristic
C. external characteristic
D. load characteristic
Answer: A
Clarification: Armature characteristic is also known as regulation characteristic. It is so called due to the fact that the difference in the terminal voltage helps to determine the voltage deviation.
6. The air gap line represents _________
A. magnetic behaviour of the air gap of the dc machine
B. magnetic behaviour of the air gap of the induction machine
C. magnetic behaviour of the iron core
D. all of the mentioned
Answer: A
Clarification: Air gap line in the magnetization curve represents the ideal nature of the machine considering no saturation for the dc machine.
7. Why is armature of a dc machine made of silicon steel stampings?
A. To reduce hysteresis loss
B. To reduce eddy current loss
C. For the ease with which slots can be created
D. To achieve high permeability
Answer: A
Clarification: The silicon steel has very high permeability and makes the flux past consistent. Thereby making lesser losses.
8. What losses occur in the teeth of dc generator?
A. To reduce hysteresis loss
B. To reduce eddy current loss
C. To reduce eddy current as well as hysteresis losses
D. To achieve high permeability
Answer: C
Clarification: Teeth of the machine has both eddy current losses as well as hysteresis losses.
9. For a 220-V level compound generator the terminal voltage at the half load is?
A. more than 220-V
B. same as no-load voltage
C. more than no-load voltage
D. lesser than no-load voltage
Answer: B
Clarification: In a level compound dc generator the terminal voltage remains same as no load voltage at all the loading.
300+ TOP D.C. GENERATORS Multiple choice Questions and Answers
