RRB JE Stage II : Electrical Engineering Quiz | 27th August

RRB JE Stage II exam is scheduled to be conducted from 28th August to 1st September2019. The overall merit for the selection will be made on the basis of the marks scored in stage II, so candidates need to prepare thoroughly for the second stage. To help the aspirants, Adda247 has come up with a study plan in which we will provide you daily quizzes of all technical subjects. The below quiz will be helpful for the candidates who opted Electrical as the exam group in RRB JE stage II. 

Q1. The energy in joules stored in the magnetic field of 0.15 H inductance with a 180mA current will be
(a) 2.43
(b) 2.43×10^(-3)
(c) 2.43×10^(-6)
(d) 2.43×10^(-9)

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Q2. A 4-pole, 3-phase induction motor is running at 4% slip at full load. If the speed of the motor is 750 rpm, the supply frequency is
(a) 16(2/3) Hz
(b) 26 Hz
(c) 50 Hz
(d) 60 Hz

Q3. Two coils ‘1’ and ‘2’ lie in parallel planes. The current through ‘1’ is changed as shown in Fig. which of the following statement about coil ‘2’ is necessarily true ?
(a) Maximum e.m.f. will be induced during LM
(b) The voltage of the coil will be zero during PQ
(c) Positive voltage induced in the coil during OL is equal and opposite to voltage drop during MP
(d) Flux will decrease during MP

S3. (d)
Sol.In portion MP, current is reducing with respect to time.
So, flux will also reduce for this portion.

Q4. Synchronous-induction coupled motors are required for
(a) high starting torque applications
(b) high pull out torque applications
(c) high running torques applications
(d) none of the mentioned

S4. (a)
Induction motor provides high starting torque with proper values of slip ring terminal resistance. Coupled along with the synchronous motor it acts as an independent set and be employed in high torque application.

Q5.The inductance of the following circuit across A and B will be
(a) L_1+L_2–M
(b) L_1+L_2+M
(c) L_1+L_2+2M
(d) L_1+L_2–2M

Q6. Which of the following can be used for braking purposes in electric trains?
(a) Induction generator
(b) Induction motor
(c) Dc series motor
(d) Dc differentially compounded generator

S6. (a)
Induction generator runs at a speed greater than the synchronous speed. To apply in braking purposes the induction generator can be run in the opposite direction to that of the operating machine direction and stopped.

Q7. Resistance of a wire always increases if
(a) temperature is reduced.
(b) independent to temperature
(c) number of free electrons available become less.
(d) number of free electrons available become more.

S7. (d)
Resistance always increases when number of free electrons available become more.

Q8. A synchronous motor absorbing 60 kW is connected in parallel with an continuous load of 240 kW operating at 0.8 power factor lag. What is the kVAR supplied by the synchronous motor to obtain a total power factor of 0.9 lagging?
(a) 35, leading
(b) 35, lagging
(c) 145, leading
(d) None of the mentioned

S8. (a)
Total power = 240 + 60 = 300 kW
cos(ø) = 0.90. Total reactive power = P × tan(ø) = 300 × tan (25.8) = 180 kVAR Load kVAR = 240 × tan (36.87) = 180 kVAR
kVAR supplied by the motor = 145-180 = -35 or k3 kVAR leading.

Q9. Two wire A and B of the same material and length L and 2L have radius r and 2r respectively.  The ratio of their specific resistances will be
(a) 1 : 1.
(b) 1 : 2.
(c) 1 : 4.
(d) 1 : 8.

S9. (a)
If material is same the ratio of specific resistance = 1 :1

Q10. _______ generator is used in arc welding purposes.
(a) Differential compound dc
(b) Dc series
(c) Cumulative compounded dc
(d) Shunt

S10. (a)
The external characteristics of the differentially compound generator have minimum voltage for the high current voltages. This is best-harnessed feature for a high current requirement by the welding application.

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