Objective Electrical Engineering For SAIL MTT Jobs

Objective Electrical Engineering For SAIL MTT Jobs
Solved electrical engineering Exam Questions FOR SAIL
Practice paper for SAIL Management Trainee vacancy



1. When bundle conductors are used in place of single conductors, the effective inductance and capacitance will respectively
(a) Increase and decrease
(b) Decrease and increase
(c) Decrease and remain unaffected
(d) remain unaffected and increase

Ans:-B


2. A balanced 3-phase, 3-wire supply feeds balanced star connected resistors. If one of the resistors is disconnected, then the percentage reduction in load will be
(a) 33(1/3)
(b) 50
(c) 66(2/3)
(d) 75

Ans:-A


3. A long overhead transmission line is terminated by its characteristic impedance. Under this operating condition, the ratio of the voltage to the current at dfferen1pñnts along the line will
(a) Progressively increase from the sending-end to the receiving-end
(b) Progressively increase from the receiving- end to the sending-end
(c) remain the same at the two ends, but be higher between the two ends being maximum at the centre of the line
(d) Remain the same at all points

Ans:-D


4. For a transmission line with negligible losses, the lagging reactive power (VAR) delivered at the receiving-end, for a given receiving-end voltage, is directly proportional to the
(a) Square of the line voltage drop
(b) Line voltage drop
(c) Line inductive reactance
(d) Line capacitive reactance

Ans:-B





5. Earth wire on EHV overhead transmission line is provided to protect the line against
(a) Lightning surges
(b) Switching surges
(c) Excessive fault voltages
(d) Corona effect

Ans:-A



6. Consider the following statements about distance relays
1. The effect of an arc may cause the relay to under reach.
2. The effect of an intermediate current source may cause the relay to overreach.
3. The effect of an intermediate load may cause the relay to under reach.
4. The presence of dc offset in the fault current may cause the relay to over- reach.
Of these statements:
(a) 2 and 3 are correct
(b) 1 and 4 are correct
(c) 1. 2 and 3 are correct
(d) 2, 3 and 4 are correct

Ans:-C





Directions: The following 13 items consist of two statements, one labelled the ‘Assertion A’ and the other labelled the ‘Reason R’. You are to examine these two statements carefully and decide f the Assertion A and the Reason R are individually true and if so, whether the Reason is a correct explanation of the Assertion. Select your answer to these Items using the codes given below and mark your answer sheet accordingly.
Codes:
(a) Both A and R are true and R is the correct explanation of A
(b) Both A and R are true but R is not a correct explanation of A
(c) A is true but R is false
(d) A is false but R is true

7. Assertion (A): Whenever a synchro pair is used as an error detector, a two-phase ac motor may be used as an actuator.
Reason (R) : the synchro pair produces an error voltage which is suppressed carrier modulated and a two-phase ac motor could demodulate this.

Ans:-C


8. Assertion (A): The input impedance of a loss- less transmission line can have two limiting values, zero and infinity.
Reason (R) : These limiting values will depend upon whether the transmission line is open or shorted at the load end and whether the length of the line is an integral multiple of λ/4 where λ is the wavelength within the transmission line.

Ans:-A


9. Assertion (A) : In order to produce a light spot at the point at which the electron am strikes the CR0 screen, the inner surface of the screen is coated with a phosphor.
Reason (R) : The phosphor absorbs the kinetic energy of the bombarding electrons and reemits energy at a higher frequency

Ans:-B


10. Assertion (A) : Frequency modulation systems are more widely used than amplitude modulation systems.
Reason (R): Frequency modulation systems have less noise than amplitude modulation systems.

Ans:-C



11. Assertion (A): Low resistances are not measured by Wheatstone bridge arrangements.
Reason (R) : The effects of contact and lead resistances detrimental to low resistance measurements, are present in large amounts in Wheatstone bridge method.

Ans:-A


12. Assertion (A): Multistage dc amplifiers are invariably based on two-transistor differential amplifiers.
Reason (R): Two-transistor differential amplifiers have high gain and high CMRR.

Ans:-A


13. Assertion (A): DC shunt motors are usually fitted with interpoles.
Reason (R) : Interpoles increases the starting torque of dc shunt motors.

Ans:-C


14. Assertion (A): In a level compounded dc generator, the terminal voltage at full load is equal to the terminal voltage at no-load.
Reason (R): Under load conditions, the armature reaction increases the flux per pole and thus helps maintain a constant terminal voltage.

Ans:-A


15. Assertion (A): DC series motors are known to be capable of operating on ac supply as well. With a very minor modification, dc shunt motors can work on ac supply as well.
Reason (R): the direction of torque developed in a rotating machine remains unaltered if the directions of conductor current and air-gap flux are reversed simultaneously.

Ans:-C


16. Assertion (A): In the experimental determination of synchronous impedance of an ac generator, it is possible to take one set of data only from short- circuit test, and obtain there from the short circuit characteristic of the machine as a straight line passing through the origin of the plot.
Reason (R): During the short-circuit test, the magnetic circuit of an alternator; remains unsaturated even when the field excitation is high.

Ans:-B

17. Assertion (A): Under normal operating conditions, major portion of iron losses of an induction motor occurs in the stator.
Reason (R): The frequency of the rotor currents under normal operating conditions is very small.

Ans:-A

18. Assertion (A) Solid state regulators are finding favour in speed control of domestic fans, over conventional resistance and inductance type regulators.
Reason (R): Solid state regulators are compact, relatively less expensive, energy efficient, more reliable and afford noise-free operation.

Ans:-A

19. Assertion (A): The conductors are usually transposed in transmission lines.
Reason (R): The resistance of each phase has to be equal.

Ans:-C


20. For the network function
Z(s) = 2 (s2 + 1)(s2 + 9) / s(s2+4)
the value of the series capacitance in Foster Form I is
(a) 1/9 F
(b) 3/9 F
(c) 2/9 F
(d) 4/9 F

Ans:-C





21. Match List I with List II and select the correct answer using the codes given below the lists
List I
(Time functions)
A. e-2(t-2)
B. d (t2) / dt
C. t /2

List II
(Laplace transforms)
1. 2 / s2
2. 1 / s+2 e-2s
3. 1 / 2s2
4. 1 / 2s
Codes:
A B C
(a) 2 1 3
(b) 2 3 4
(c) 1 2 3
(d) 3 1 4

Ans:-A


22. When a constant voltage source V is connected to a series R-L circuit with zero initial stored energy in the inductor, the instantaneous value of power supplied to the inductor I is given by
(a) V2/R (e –Rl/L — e-2Rt/L)
(b) V2/R (1 — e-Rt/L)
(c) V2/R e-Rt/L
(d) V2/R(1 + e-Rt/L)

Ans:-B


23. Consider the following statements
In a series RLC resonant circuit, the bandwidth is
1. Directly proportional to resonant frequency
2. Inversely proportional to resonant frequency
3. Directly proportional to quality factor
4. Inversely proportional to quality factor
Of these statements:
(a) 2 and 3 are correct
(b) 2 and 4 are correct
(c) 1 and 3 are correct
(d) 1 and 4 are correct

Ans:-D





24. The instantaneous power taken by a balanced three-phase load supplied from a balanced three- phase source it
(a) Zero
(b) A constant
(c) A pulsating function with a non-zero average
(d) Alternating with a zero average

Ans:-B


25. The power in a 3-phase 3-wire load Is measured using two 100 W full-scale wattmeters W1 and W7 WI is of accuracy class ±1% and reads 100 W. W2 is of accuracy class ±0.5% and reads —50 W. Then the uncertainty In the computation of total power it
(a) ± 1.5%
(b) ± 0.5%
(c) ±4%
(d) ±3%

Ans:-D