Electrical Engineering Frequently Asked Questions in IES/ESE and PSU

1.      The unit of magnetic flux density is

a.     gauss

b.     tesla

c.      bohr

d.     weber per sec

»  Ans► tesla

2.     Match List-I with List-II and select the correct answer using the code given below the Lists :
A.Antiferro-magnetic 1.Permanent magnetic dipoles
B.Ferri-magnetism 2.Dipoles interact or line up in parallel
C.Dia-magnetic 3.Neighbouring magnetic moments are aligned anti parallel with equal magnitudes
D.Ferro-magnetic 3.Neighbouring magnetic moments are aligned anti parallel with unequal magnitudes

a.     a4b3c1d2

b.     a2b3c1d4

c.      a4b1c3d2

d.     a2b1c3d4

»  Ans► a4b1c3d2

3.     Skin depth is the distance from the conductor surface where the field strength has fallen to

a.     pi of its strength at the surface

b.     e of its strength at the surface

c.      (1/e) of its strength at the surface

d.     (1/pi.e) of its strength at the surface

»  Ans► (1/e) of its strength at the surface

4.     A signal of 10 V is applied to a 50

a.     6 V

b.     10 V

c.      0 V

d.     1 V

»  Ans► 6 V

5.     The magnetic flux density created by an infinitely long conductor carrying a current t at a radial distance R is ————————–.

6.     The electric field in the vicinity of two oppositely charged parallel conductors is

a.     radial uniformly

b.     in parallel lines between the two imaginary parallel planes passing through the centres of the two conductors

c.      not uniform and its direction changes from point to point

d.     in parallel circular paths between the two conductors,with the centre of the circles located at the mid-point of a line joining the two centres of the two conductors

»  Ans► not uniform and its direction changes from point to point

7.     Two charges are placed at a distance apart.Now,if a glass slab is inserted between them,then the force between the charges will

a.     reduce to zero

b.     increase

c.      decrease

d.     not change

»  Ans► decrease

8.     What is the effect of lag compensator on the system bandwidth and the signal-to-noise ratio?

a.     Bandwidth is increased and signal-to-noise ratio is improved

b.     Bandwidth is increased and signal-to-noise ratio is deteriorated

c.      Bandwidth is increased and signal-to-noise ratio is deteriorated

d.     Bandwidth is reduced and signal-to-noise ratio is improved

»  Ans► Bandwidth is increased and signal-to-noise ratio is deteriorated

9.     The following point charges are located in air : +0.008 +.054

a.     0.058

b.     0.049

c.      0.029

d.     0.016

»  Ans► 0.049

10.  Electric flux through a surface area is the integral of the

a.     normal component of the electric field over the area

b.     parallel component of the electric field over the area

c.      normal component of the magnetic field over the area

d.     parallel component of the magnetic field over the area

»  Ans► normal component of the electric field over the area

11.   The presence of one of the following materials,in iron or steel for use as a magnetic material,tends to reduce the hysteresis loss

a.     Carbon

b.     Sulphur

c.      Phosphorus

d.     Silicon

»  Ans► Silicon

12.  The angle between two adjacent asymptotes in a root locus diagram is

a.     pi/n+m

b.     2.pi/n+m

c.      pi/n-m

d.     2.pi/n-m

»  Ans► 2.pi/n-m

13.  The equation of continuity defines the relation between

a.     electric field and magnetic field

b.     electric field and charge density

c.      flux density and charge density

d.     current density and charge density

»  Ans► current density and charge density

14.  As a result of reflections from a plane conducting wall,electromagnetic waves acquire an apparent velocity greater than the velocity of light in space. This is called

a.     velocity propagation

b.     normal velocity

c.      group velocity

d.     phase velocity

»  Ans► phase velocity

15.  A 75 Ω transmission line is first short-terminated and the minima locations are noted. When the short is replaced by a resistive load R,the minima locations are not
altered and the VSWR is measured to be 3. The value of R is

a.     25

b.     50

c.      225

d.     250

»  Ans► 25

16.  The depth of penetration of a wave in a lossy dielectric increases with increasing

a.     conductivity

b.     permeability

c.      wavelength

d.     permittivity

»  Ans► conductivity

17.  Match List-I with List-II and select the correct answer using the code given below the Lists :
A.Carbon(Diamond) 1.Conducting
B.Silicon 2.Semi-conducting
C.Tin (Grey) 3.Insulating
D.Lead

a.     a3b2c1d1

b.     a1b2c1d3

c.      a3b1c2d1

d.     a1b1c2d3

»  Ans► a3b2c1d1

18.  It is possible to destroy the super-conductivity of a material by applying

a.     a strong magnetic field

b.     a temperature much below the transition temperature

c.      strong electric field

d.     a pressure below that of the atmosphere

»  Ans► a strong magnetic field

19.  The maximum power will be transferred from a voltage source to a load when

a.     the source impedance is half that of the load impedance

b.     the source impedance is equal to that of the load impedance

c.      the source impedance is twice that of the load impedance

d.     both source and load impedance must be zero

»  Ans► the source impedance is equal to that of the load impedance

20. For a series and a parallel circuit,the equivalent total value of certain parameter X is given by
Xe = X1 + X2+X3 +X4 +___+X1
where X; is the ith value of the parameter and Xe is the equivalent value, and n is the number of elements. The parameter X can be

a.     resistance

b.     current

c.      voltage

d.     power

»  Ans► voltage

21.  A coil having 250 turns is connected to a 50 V DC source.If the coil resistance is 10Ω, the m.m.f. (magneto-motive force) developed in AT would be

a.     500

b.     1250

c.      2500

d.     500

»  Ans► 1250

22. A single-phase energy meter having meter constant of 200 rev/kWh is operating on 230 V,50 Hz supply with a load of 10 A, and at unity power factor for three hours continuously.The number of revolutions shown by the meter during this period is

a.     13800

b.     1380

c.      276

d.     138

»  Ans► 1380

23. A3-phase,4-wire system supplies power to a balanced star-connected load. The current in each phase is 15 A. The current in the neutral wire will be

a.     15

b.     45

c.      8.66

d.     0

e.     Ans►

24. In a linear network, a 1.0 resistor consumes a power of 4 W when voltage source of 4 V is applied to the entire circuit, and16 W when the voltage source is replaced by an 8 V source. The power consumed by the 192 resistor when 12 V is applied will be

a.     20

b.     36

c.      144

d.     38

»  Ans► 36

25. Consider the following statements Any element connected in
1.series with a voltage source is redundant
2.parallel with a voltage source is redundant
3.series with a current source is redundant
4.parallel with a current source is redundant

a.     1,3

b.     2,3

c.      3,4

d.     1,2

»  Ans► 2,3

26. The lowest and the highest critical frequencies of R-C driving-point impedance are respectively

a.     a zero and a pole

b.     a pole and a pole

c.      a zero and a zero

d.     a pole and a zero

»  Ans► a pole and a zero

27.  For an R-L-C series circuit in resonance, the following statement is not correct

a.     The current is maximum

b.     The voltage phasors across the capacitance and inductance are unequal

c.      The voltage drop across the resistance is maximum

d.     The voltage drops across the capacitance and inductance are unequal in magnitude

» Ans► The voltage drops across the capacitance and inductance are unequal in magnitude

28. A coil of resistance 200 and inductance 0.8 H is connected to a 200 V DC supply.The rate of change of current at t = 0+ is

a.     16

b.     160

c.      250

d.     4000

»  Ans► 250

29. The number of independent KVL and KCL equations for a network with n nodes and I links are respectively

a.     l and n

b.     l and n-1

c.      n-1 and l

d.     n-1 and l-1

»  Ans► l and n-1

30. The total number of branches in a network is equal to b. The graph of the network has n number of branches. The minimum number of line currents is

a.     b+n

b.     b

c.      b-n

d.     n

»  Ans► b

31.  When a unit impulse voltage is applied to an inductor of 1H, the energy supplied by the source is

a.     2 J

b.     1 J

c.      .5 J

d.     .25 J

»  Ans► .5 J

32. When a steady current is passed through a ballistic galvanometer,then the deflection will be

a.     maximum

b.     zero

c.      twice the normal value as it depends on Hibbert magnetic standard

d.     none of the above

»  Ans► zero

33. The measurement of frequency can be carried out with

a.     Owen’s bridge

b.     Wien’s bridge

c.      Maxwell’s inductance- capacitance bridge

d.     Schering’s bridge

»  Ans► Wien’s bridge

34. An angular deflection type indicating PMMC meter is provided with spring control and

a.     damping by air dashpot

b.     electromagnetic damping in the aluminium former only

c.      electromagnetic damping in the aluminium former and the moving coil as well

d.     no damping

»  Ans► electromagnetic damping in the aluminium former only

35. An advantage of PMMC instrument is that it

a.     is free from friction error

b.     has high torque-to-weight ratio of moving parts

c.      has low torque-to-weight ratio

d.     can be used on both AC and DC

»  Ans► has high torque-to-weight ratio of moving parts

36. The following is not essential for the working of an indicating instrument

a.     Deflecting torque

b.     Breaking torque

c.      Damping torque

d.     Controlling torque

»  Ans► Breaking torque

37.  Systematic error of an instrument for measurement can be minimized by

a.     selecting a proper measuring device for the particular application

b.     calibrating the measuring device against a standard device

c.      applying correction factors for change of ambient conditions

d.     carrying out all of it above

»  Ans► carrying out all of it above

38. The following material is not used for making a piezoelectric transducer

a.     Rochelle salt

b.     Banium titanate

c.      Chlorium sulp

d.     Quartz

»  Ans► Chlorium sulp

39. A linear displacement digital transducer uses

a.     BCD code

b.     Gray code

c.      hexadecimal code

d.     binary code

»  Ans► Gray code

40. An electronic voltmeter gives more accurate readings in high-resistance circuits as compared to a non-electronic voltmeter because of its

a.     low meter resistance

b.     high kQ/V rating

c.      high V/kQ rating

d.     high resolution

»  Ans► high kQ/V rating

41.  By mistake, an ammeter is used as a voltmeter. In all probabilities, it will

a.     give much higher reading

b.     give extremely low reading

c.      indicate no reading at all

d.     get damaged

»  Ans► get damaged

42. The meter constant of a single-phase energy meter is 500 rev/kWh. It is found that with a load of 5 kW, it makes 40 revolutions in 50 sec. The percentage error is

a.     5.25%

b.     10.5%

c.      15.25%

d.     20%

»Ans► 20%

43. A shunt resistance of 25 Ω is required for extending the range of an ammeter from 100

a.     25

b.     50

c.      100

d.     1000

»Ans► 100

44. Which of the following are the objectives of a data acquisition system? 1.It must acquire necessary data at correct speed and time. 2.It must collect and store data. 3.There should be provision for real-time data display. 4.There should be provision for stored data display on request. (a)1,2 and 3 only
(b)1,3 and 4 only
(c)1,2, 3 and 4
(d)2,3 and 4 only

a.     a

b.     b

c.      c

d.     d

»  Ans► c

45. The pressure in a tank varies from 20 psi to 100 psi. The pressure in the tank is desired to be kept at 50 psi. The full-scale error when the pressure inside the tank is 30 psi will be

a.     35

b.     25

c.      40

d.     15

»  Ans► 25

46. Analog data acquisition systems are used when

a.     wide bandwidth and low accuracy are required/ sufficient

b.     narrow bandwidth and low accuracy are required/ sufficient

c.      wide bandwidth and high accuracy are required

d.     narrow bandwidth and high accuracy are required

»  Ans► narrow bandwidth and low accuracy are required/ sufficient

47.  An LVDT is used to measure 1 mm displacement for which a voltmeter of range 0 to 2 V through an amplifier having a gain of 500 is connected at the output of the LVDT. If the output of the LVDT is 2 mV,then the sensitivity of the instrument will be

a.     1 V/mm

b.     .5 V/mm

c.      .1V/mm

d.     .05 V/mm

»Ans► 1 V/mm

48. The expansion for the acronym LVDT,a transducer used for displacement measurement, is

a.     low voltage displacement transducer

b.     light vision displacement transducer

c.      linear variable displacement transducer

d.     linear variable differential transformer

»Ans► linear variable differential transformer

49. When compared with other transducers measuring temperature, a four-lead platinum RTD 1.has better linearity over a wide operating range 2.has better accuracy and precision 3.has better stability at high temperature 4.is inexpensive .Which of these are correct?
(a)1,2 and 3
(b)1,2 and 4
(c)1,3 and 4
(d)2,3 and 4

a.     a

b.     b

c.      c

d.     d

»  Ans► a

50. A frequency counter can be used for the measurement of 1.fundamental frequency of input signal
2.time interval between two pulses . Which of these is/are correct? (a)1 only
(b)2 only
(c)Neither 1 nor 2
(d)Both 1 and 2

a.     a

b.     b

c.      c

d.     d

»  Ans► a

51.  Modern electronic multimeter measure resistance by

a.     taking advantage of an electronic bridge compensator for nulling

b.     forcing a constant current and measuring the voltage across unknown resistance

c.      using a bridge circuit

d.     applying a constant voltage across the unknown resistance and measuring the current through it

»  Ans► forcing a constant current and measuring the voltage across unknown resistance

52. Guard circuits are used in insulation resistance measurements to

a.     increase the range of resistance values measured

b.     reduce the effect of leakage current on measurement

c.      protect against external electric fields

d.     protect against external magnetic fields

»  Ans► reduce the effect of leakage current on measurement

53. The preferred methods of measuring low resistance and the resistance of cable insulation are respectively

a.     V/I method and loss-of-charge method

b.     Kelvin’s double bridge and Megger test

c.      Wheatstone bridge and Kelvin’s double bridge

d.     potentiometer method and Wheatstone bridge

»  Ans► Kelvin’s double bridge and Megger test

54. The law/principle in mechanical systems, analogous to Kirchhoff laws in electrical systems, is

a.     first law of motion

b.     second law of motion

c.      third law of motion

d.     d Alembert principle

»  Ans► d Alembert principle

55. A second-order control system exhibits 100% overshoot.Its damping coefficient is

a.     greater than 1

b.     less than I

c.      equal to 0

d.     equal to 1

»  Ans► equal to 0

56. By using feedback in control systems,the sensitivity to parameter variation is improved.This is achieved at the cost of

a.     stability

b.     loss of system gain

c.      transient response

d.     reliability

»  Ans► transient response

57.  The open-loop transfer function of a control system is 10/s+1.The steady state error due to unit step input signal when operated as a unity feedback system is

a.     10

b.     1/11

c.      infinity

d.     Ans► /11

58. The impulse response of a linear system is e to the power -t, t > 0.The corresponding transfer function is

a.     1/(s.s+1)

b.     1/(s+1)

c.      1/s

d.     s/(s+1)

»  Ans► 1/(s+1)

59. The sensitivity of an overall transfer function m(s) of a closed-loop control system with respect to the forward path transfer function G(s) is

a.     G/1+GH

b.     G/1-GH

c.      1/1-GH

d.     1/1+GH

»  Ans► G/1-GH

60. The characteristic equation of a control system is given below : F(s)=s4+s3+3s2+2s+5=0 (read numbers after s as power to s like s4 is s to the power 4) The system is

a.     stable

b.     critically stable

c.      conditionally stable

d.     unstable

»  Ans► unstable

61.  Addition of open-loop poles results into which of the following?

a.     Root locus shifts towards imaginary axis

b.     Root locus shifts away from imaginary axis

c.      System stability increases

d.     System becomes less oscillatory

»  Ans► Root locus shifts towards imaginary axis

62. The open-loop transfer function of a unity feedback control system is G(s) = 1/(s + 2)2. The closed-loop transfer function will have poles at

a.     -2, -2

b.     -2, -1

c.      -2,+2

d.     -2

»  Ans► -2

63. The phase-lead compensation is used to

a.     increase rise time and decrease overshoot

b.     decrease both rise time and overshoot

c.      increase both rise time and overshoot

d.     decrease rise time and increase overshoot

»  Ans► decrease rise time and increase overshoot

64. The open-loop transfer function of the feedback control system is given by G(s)=k/(s+1)(s+2)(s+3).The breakaway point in its root locus will be

a.     between -2 and -3

b.     between -1 and -2

c.      between 0 and -1

d.     beyond -3

»  Ans► between -1 and -2

65. Given a badly under damped control system,the type of cascade compensator to be used to improve its damping is

a.     phase-lead

b.     phase-lag

c.      phase-lag-lead

d.     notch filter

»  Ans► phase-lead

66. The compensator Gc(s)=5(1+.3s)/1+.1s would provide a maximum phase shift of

a.     20 degree

b.     30 degree

c.      45 degree

d.     60 degree

»  Ans► 30 degree

67.  The following transfer function represents a phase-lead compensator

a.     s+4/s+6

b.     4s+2/6s+1

c.      s+4/3s+6

d.     1/s

»  Ans► s+4/s+6

68. A non-linear control system is described by the equation Θ+KsinΘ=0. The type of singular point at (0, 0) is

a.     centre

b.     focus

c.      saddle point

d.     None of the above

»  Ans► centre

69. In position control systems,the device used for providing rate feedback is called

a.     potentiometer

b.     synchro

c.      tachogenerator

d.     servomotor

»Ans► tachogenerator

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