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SSC JE Electrical Machines Quiz 85

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Question 1

Neglecting all losses how is the developed torque (T) of a dc separately excited motor operating under constant terminal voltage, related to its output power (P)?

Question 2

Match List-I (Machine characteristic) with List-II (Quantity) and select the correct answer using the code given below the lists:
List-I
A) Open-circuit characteristic
B) V-curve
C) Internal characteristic
D) Inverted V-curve
List-II
1) p.f. vs. I_f
2) E_a vs. I_a
3) E_g vs. I_f
4) I_a vs. I_f

Question 3

The ratio of primary/secondary voltages in a step-down transformer is 2:1. The saving in terms of weight of copper required if an autotransformer is used instead of a two-winding transformer will be

Question 4

Cores of large power transformers are made from which one of the following?

Question 5

A dc series motor is running at rated speed and rated voltage, feeding a constant power load. If the speed has to be reduced to 0.25 p.u., the supply voltage should be reduced to

Question 6

Consider the following parts of a dc machine :
1) Yoke
2) Armature core
3) Brushes
4) Pole core
Which of the above parts are subjected to iron loss?

Question 7

Match List-I (DC machine quantity) with List-II (Relation) and select the correct answer using the code given below the lists :

Question 8

Which of the following are true is respect of interpoles in dc machines ?
1) Reduce armature reaction effects in interpolar region.
2) Windings are connected in series with armature
3) Have the same dimensions as main poles.
Select the correct answer using the code given below

Question 9

A 400V D.C. shunt motor takes 5A at no-load. R_a = 0.5 ohms, R_i = 200 ohms. What is the ratio of speed from full load to no-load, when the D.C. shunt motor lakes 50 A on full load?

Question 10

The speed of repulsion motor at no load will be:

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