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Browse complete papersThe Norton equivalent of the circuit shown in figure at terminals a-b are __________.
RN = 4Ω, IN = 1 A
RN = 4Ω, IN = 2 A
RN = 25Ω, IN = 1 A
RN = 25Ω, IN = 3 A
Correct answer
RN = 4Ω, IN = 1 A
Which set of statements correctly describes the steady state speed-torque characteristics of a three-phase synchronous motor?
i) Runs at constant synchronous speed
ii) Starting torque is zero
iii) Torque increases significantly with slip
iv) Not suitable for variable speed drives
v) Maintains speed under varying loads
(i), (ii), and (v) only
(i), (ii), (iii) and (v) only
(i), (ii), (iii) and (iv) only
(i), (iii), (iv) and (v) only
Correct answer
(i), (ii), and (v) only
Which of the following balanced phase-voltage phasor sets represents an abc positive-sequence system?
Va = 0°, Vb = 120°, Vc = -120°
Va = 0°, Vb = 90°, Vc = 180°
Va = 0°, Vb = -90°, Vc = -180°
Va = 0°, Vb = -120°, Vc = 120°
Correct answer
Va = 0°, Vb = 120°, Vc = -120°
For accurate measurement of inductors using Hay's bridge, which characteristic should the inductor primarily possess?
High resistance
Low Q-factor
High Q-factor
Medium Q-factor
Correct answer
High resistance
Which of the following sets of statements about the causes of errors in current transformers is correct?
i) Leakage reactance in secondary winding contributes to ratio error
ii) High magnetizing current increases phase angle error
iii) Burden with low power factor increases phase angle error
iv) Core saturation reduces both ratio and phase angle errors
(ii) and (iv) only
(iii) and (iv) only
(i) and (iv) only
(i), (ii) and (iii) only
Correct answer
(ii) and (iv) only
What does the Reduction Factor in illumination refer to?
The percentage of light lost due to reflection and absorption
The ratio of actual illuminance to theoretical illuminance
The ratio of the illumination at a given point to the initial illumination
The ratio of total luminous flux to the consumed electrical power
Correct answer
The percentage of light lost due to reflection and absorption
Which of the following devices provide rapid fault current interruption independently in a high-voltage power distribution system?
Contactor
Linear coupler
HRC fuse
Isolator
Correct answer
Contactor
A protective device with high rupturing capacity can:
Improve voltage regulation of transformers during overload conditions
Increase insulation resistance during normal system operating conditions
Reduce transmission line inductance during balanced load operation only
Safely interrupt heavy fault currents without equipment damage occurrence
Correct answer
Improve voltage regulation of transformers during overload conditions
A three-phase slip ring induction motor is preferred over a squirrel cage induction motor for which of the following application scenarios?
When highest efficiency is the only concern
When constant speed under all load conditions is needed
When variable speed and high starting torque are required
When reduced maintenance is the top priority
Correct answer
When highest efficiency is the only concern
The speed of a synchronous motor depends on:
Field resistance
Supply frequency
Armature current
Load only
Correct answer
Field resistance