2019 SSC Junior Engineer Electrical Online Exam 2019 CPWD/CWC/MES Electrical Engineering Set 2.5

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41. Braking is used where, load on the motor has very high inertia (in electric trains) ?




... Answer is C)
Regenerative braking is used where, load on the motor has very high inertia (e.g in electric trains).
___ As generated emf is greater than applied voltage (machine is acting as a DC generator), power will be returned to the line, this action is called as regeneration.


42. Form Factor × Peak Factor = ?




... Answer is A)
The form factor of an AC waveform is the ratio of its RMS value divided by its average value.

Peak Factor is defined as the ratio of maximum value to the R.M.S value of an alternating quantity.
The alternating quantities can be voltage or current.


43. Conductors experience skin effect in ?




... Answer is B)
Skin effect is the tendency of an alternating electric current (AC) to become distributed within a conductor such that the current density is largest near the surface of the conductor and decreases exponentially with greater depths in the conductor.

44. A circuit consists of two parallel resistors, having resistance of 20Ω and 30Ω respectively connected in series with 15Ω. If the current through the 15Ω resistor is 3A, then find the current through 20Ω and 30Ω resistors respectively ?




... Answer is C)


45. An ideal voltage source is one that ?




... Answer is c)
An ideal voltage source is a voltage source that supplies constant voltage to a circuit despite the current which the circuit draws.
The internal resistance of an ideal voltage source is zero


46. If the number of poles in an 11KV transmission line is 80, then how many disc insulators are required ?




... Answer is A)
No of disc required for 11 kV transmission line = 1 disc

Since the transmission line is 3-phase, therefore, the number of discs required for a single-pole will be 3.

Total no. of poles = 80

No of disc = 3 × 80 = 240



47. Which of the following comes under the category of single phase commutator motors ?




... Answer is D)
The single-phase series motor is a commutator-type motor.
The motor will continue to run in the same direction if the polarity of the line terminals of a dc series motor are reversed.

Motors that can be used with a single-phase ac source as well as a dc source are called universal motors.

48. IL = Load Current, then the relation between these currents for a DC series generator is ?




... Answer is A)
all armature, field, and load are in series they carry the same current.

49. A transistor can be made to operate as a switch by operating it in which of the following regions ?




... Answer is D)
The four transistor operation modes are:

#-Saturation -- The transistor acts like a short circuit.As close switch. Current freely flows from collector to emitter.
#-Cut-off -- The transistor acts like an open circuit.As open switch. No current flows from collector to emitter.
#-Active -- The current from collector to emitter is proportional to the current flowing into the base.
#-Reverse-Active -- Like active mode, the current is proportional to the base current, but it flows in reverse.
Current flows from emitter to collector (not, exactly, the purpose transistors were designed for).


50. Which of the following instruments has uniform scale ?




... Answer is B)
PMMC instrument gives uniform scale because: It uses spring control and The deflection torque is proportional to the instrument current.











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