Abirami Subramanian: May 2014

1. Which of the following statements is/are true for the diamond structure?
i. Coordination number is four

ii. Packing fraction is 0.34

iii. Copper crystallizes into diamond structure

iv. Lattice is FCC

Select the correct answer using the codes given below:

a) i only

b) i,ii and iv

c) ii and iii only

d) ii, iii and iv

Ans: Option b)

2. Which of the following statements is/are true for a good conductor of electricity?

i. Its conductivity decreases with increasing temperature

ii. Number of free electrons is around 10²⁶ m^-3

iii. Its conductivity decreases with addition of impurities

iv. It is a good conductor of heat also

Select the correct answer using the codes given below:

a) i, ii, iii and iv

b) i only

c) ii and iii only

d) iii and iv only

Ans: Option a)

3. Which of the following materials is not an insulator?

a) Diamond

b) Graphite

c) Bakelite

d) Lucite

Ans: Option b)

4. Consider the following statements:

The conductivity of a metal has negative temperature coefficient since:

i. The electron concentration increases with temperature

ii. The electron mobility decreases with temperature

iii. The electron-lattice scattering rate increases with temperature.

Which of the above statements is/are correct?

a) i only

b) i and ii

c) ii and iii

d) iii only

Ans: Option c)

5. Which of the following is not conducting material?

a) Copper

b) Tungsten

c) Germanium

d) Platinum

Ans: Option c)

6. What is the chemical bonding in silicon semiconductor?

a) Metallic

b) Ionic

c) Covalent

d) Van der Waals

Ans: Option c)

7. Which of the following is a trivalent material?

a) Antimony

b) Phosphorous

c) Arsenic

d) Boron

Ans: Option d)

8. The fuse material used in electrical lines must have which one of the following properties?

a) High resistivity

b) Low conductivity

c) High melting point

d) Low melting point

Ans: Option d)

9. Manganin, an alloy of copper and manganese is used in

a) Soldering material

b) Heating elements

c) Ballast resistors

d) Standard resistances

Ans: Option d)

10. Which if the following pairs is not correctly matched?

a) NaCl Diamagnetic

b) Gd Paramagnetic

c) Ferrite Ferrimagnetic

d) Cr2O3 Ferromagnetic

Ans: Option b)

11. Hysteresis loss in a transformer working at 220 V and at frequency of 50 Hz is 100 W. When the transformer is operated at 220 V and at a frequency of 100 Hz, What is the hysteresis loss?

a) 50 W

b)100 W

c) 200 W

d) 400 W

Ans: Option c)

12. Which of the following is not an electro-magnetic device?

a) Hall Transducer

b) Transformer

c) Speedometer

d) Eddy current damping device

Ans: Option a)

13. Which one of the following materials is used for making permanent magnets?

a) Steel

b) Carbon

c) Carbon-Steel

d) Graphite

Ans: Option c)

14. What happens when a paramagnetic material is heated above Curie temperature?

a) It becomes diamagnetic

b) It becomes non-magnetic

c) It becomes ferromagnetic

d) It becomes anti-ferromagnetic

Ans: Option a)

15. Ferromagnetic materials show hysteresis in B-H characteristic. As the magnetic field is increased slowly from zero value, What is the first process which sets in the material to give net magnetization?

a) Growth of favorably oriented domains at the cost of other domains by reversible boundary displacements.

b) Growth of favorably oriented domains at the cost of other domains by irreversible boundary displacements.

c) Domain wall orientation

d) A combination of processes a) and c) above

Ans: Option d)

16. The following properties are associated with ferroelectric materials:

i) Its susceptibility is negative.

ii) The susceptibility is expressed as χ = C/ (T – Tc)

Where C is the curie temperature.

iii) It has permanent dipoles oriented randomly

Which of the above statements is/are correct?

a) i only

b) i and iii

c) ii only

d) i, ii and iii

Ans: Option c)

17. The materials not having negative temperature coefficient of resistivity are

a) Metals

b) Semiconductors

c) Insulators

d) None of the above

Ans: Option a)

18. Consider the following:

i) Si

ii) Ge

iii) GaAs

iv) InP

Which of the following semiconductors should be used for making highly efficient photodiodes?

a) i and iv only

b) iii and iv only

c) i, iii and iv

d) ii, iii and iv

Ans: Option b)

19. Which of the following compounds is widely used for making ferrites?

a) FeO

b) CuO

c) MgO

d) Fe2O3

Ans: Option d)

20. Effective Q of the equivalent electric circuit of quartz crystal is of the order of

a) 200

b) 2000

c) 20,000

d) 2,00,000

Ans: Option c)

21. In a material, the fermi-level is located between the center of the forbidden band and the conduction band. Then what is that material?

a) A p-type semiconductor

b) A n-type semiconductor

c) An intrinsic semiconductor

d) An insulator

Ans: Option b)

22. Consider the following statements:

1) Acceptor level is formed very close to the conduction band.

2) The effective mass of the free electron is same as that of a hole.

3) The magnitude of the charge of a free electron is same as that of a hole.

4) Addition of donor impurities adds holes to the semiconductor

Which of the following statements are correct?

a) 1 and 3

b) 2 and 3

c) 2 and 4

d) 3 and 4

Ans: Option b)

23. Diffusion current of holes in a semiconductor is proportional to ( with p = concentration of holes/unit volume)

a) dp/dx²

b) dp/dx

c) dp/dt

d) d²p/dx²

Ans: Option b)

24. The junction capacitance of linearly graded pn-junction (with applied voltage = VB) is proportional to

a) V_B^1/2

b)V_B^-1/2

c) V_B^1/3

d) V_B^-1/3

Ans: Option d)

25. As per Hall effect, if any specimen carrying a current I is placed in a transverse magnetic field B, then an electric field E is induced in the specimen in the direction

a) parallel to I

b) perpendicular to B and parallel to I

c) parallel to I and B

d) perpendicular to both I and B

Ans: Option d)

26. Which of the following quantities cannot be measured/determined using Hall effect?
a) Type of semiconductor ( p or n)
b) Mobility of charge carriers
c) Diffusion constant
d) Carrier concentration

Ans: Option c)

27. A junction FET can be used as a voltage variable resistor
a) at pinch-off condition
b) beyond pinch-off voltage
c) well below pinch-off condition
d) for any value of V_DS

Ans: Option c)

28. The maximum power dissipation capacity of a transistor is 50 mW. If the collector emitter voltage is 10 V, what is the safe collector current that can be allowed through the transistor?
a) 5 mA
b) 2.5 mA
c) 10 mA
d) 25 mA

Ans: Option a)

29.

The above figure shows the symbol of

a) p channel depletion MOSFET

b) p channel enhancement MOSFET

c) complementary MOSFET

d) p channel JFET

Ans: Option a)

30. Which of the following statements is correct for MOSFETs?

a) p channel MOS is easier to produce than n channel MOS

b) n channel MOS must have twice the area of p channel MOS for the same ON resistance

c) p channel MOS has faster switching action than n channel MOS

d) p channel MOS has higher packing density than n channel MOS

Ans: Option a)

31. The process of extension of a single-crystal surface by growing a film in such a way that the added atoms form a continuation of the single-crystal structure is called

a) Ion implantation

b) Chemical vapour deposition

c) Electroplating

d) Epitaxy

Ans: Option d)

32. The maximum concentration of the element which can be dissolved in solid silicon at a given temperature is termed as

a) Solid Solubility

b) Dissolution coefficient

c) Solidification index

d) Concentration index

Ans: Option a)

33. Which of the following devices is used in the microprocessors?

a) JFET

b) BJT

c) MOSFET

d) CMOS

Ans: Option d)

34. In a CMOS CS amplifier, the active load is obtained by connecting a

a) p channel current mirror circuit

b) n channel transistor

c) p channel transistor

d) BJT current mirror

Ans: Option a)

35. Which of the following is not LED material?

a) GaAs

b) GaP

c) SiC

d) SiO2

Ans: Option d)

36. The minimum energy of a photon required for intrinsic excitation is equal to

a) energy of bottom of conduction band

b) energy of top of valence band

c) forbidden gap energy

d) Fermi level

Ans: Option c)

37. Assertion (A): An unbiased p-n junction develops a built-in-potential at the junction with the n-side positive and the p-side negative

Reason (R): The p-n junction behaves as a battery and supplies current to a resistance connected across its terminals.

a) Both A and R are individually true and R is the correct explanation of A.

b) Both A and R are individually true and R is not the correct explanation of A.

c) A is true but R is false

d) A is false but R is true

Ans: Option c)

38. Assertion (A): Cut-in voltage for Germanium diode is greater than that for Silicon diode

Reason (R): Germanium diode has a higher reverse saturation current than Silicon diode.

a) Both A and R are individually true and R is the correct explanation of A.

b) Both A and R are individually true and R is not the correct explanation of A.

c) A is true but R is false

d) A is false but R is true

Ans: Option d)

39. Assertion (A): The h-parameter model of a BJT can be derived from its hybrid -π model and vice-versa.

Reason (R): The hybrid-π model has many more additional elements as compared to h-parameter model of the BJT.

a) Both A and R are individually true and R is the correct explanation of A.

b) Both A and R are individually true and R is not the correct explanation of A.

c) A is true but R is false

d) A is false but R is true

Ans: Option b)

40. Assertion (A): For same drain current rating N-channel MOSFET occupies more area than -channel MOSFET.

Reason (R): Electron mobility is much higher than hole mobility.

a) Both A and R are individually true and R is the correct explanation of A.

b) Both A and R are individually true and R is not the correct explanation of A.

c) A is true but R is false

d) A is false but R is true

Ans: Option d)

42. A signal x₁(t) and x₂(t) constitute the real and imaginary parts respectively of a complex valued signal x(t). What form of waveform does x(t) possess?
a) Real Symmetric
b) Complex symmetric
c) Asymmetric
d) Conjugate Symmetric

Ans: Option d)

43. A function of one or more variables which conveys information on the nature of physical phenomenon is called
a) Noise
b) Interference
c) System
d) Signal

Ans: Option d)

44.

Ans: Option a)

45. What is the period of the sinusoidal signal x(n) = 5 cos (0.2 π n)?
a) 10
b) 5
c) 1
d) 0

Ans: Option a)

46.

Ans: Option c)

47.

Ans: Option b)

48. Assertion (A): There are no convergence issues with the discrete-time Fourier series in general.
Reason (R): A discrete-time signal is always obtained by sampling a continuous time signal.

a) Both A and R are individually true and R is the correct explanation of A.

b) Both A and R are individually true and R is not the correct explanation of A.

c) A is true but R is false

d) A is false but R is true

Ans: Option d)

49. In the field of a charge Q at the origin, the potentials at A(2, 0, 0) and B( 1/2, 0, 0) are Va = 15 volts and Vb= 30 volts respectively. What will be the potential at C( 1, 0, 0 )?

a) 25 volts

b) 22.5 volts

c) 20 volts

d) 17.5 volts

Ans: Option b)

50. What will be the equipotential surfaces for a pair of equal and opposite line charges?

a) Spheres

b) Concentric cylinders

c) Non-concentric cylinders

d) None of the above

Ans: Option c)

51. If the potential functions V1 and V2 satisfy Laplace's equation within a closed region and assume the same values on its surface, then which of the following is correct?

a) V1 and V2 are identical

b) V1 is inversely proportional to V2

c) V1 has the same direction as V2

d) V1 has the same magnitude as V2 but has different direction

Ans: Option a)

52. By what name is the equation ∇. J = 0 frequently known?

a) Poisson's equation

b) Laplace's equation

c) Continuity equation for steady currents

d) Displacement equation

Ans: Option c)

53. Method of images is applicable to which fields?

a) Electrostatic fields only

b) Electrodynamic fields only

c) Neither electrostatic nor electrodynamic fields

d) Both electrostatic and electrodynamic fields

Ans: Option a)

54. Who developed the concept of time varying electric field producing s magnetic field?

a) Gauss

b) Faraday

c) Hertz

d) Maxwell

Ans: Option b)

55.

Ans: Option b)

56. For plane wave propagating in free space or two conductor transmission line, what must be the relationship between the phase velocity Vp, group velocity Vg and speed of light C?

a) Vp > C >Vg

b) Vp < C

c) Vp = C =Vg

d) Vp < Vg < C

Ans: Option a)

57. The reflection coefficient on a 500 m long transmission line has a phase angle of -150 degrees. If the operating wavelength is 150 m, what will be the number of voltage maxima on the line?

a) 0

b) 3

c) 6

d) 7

Ans: Option d)

58. Consider the following statements:

For a 10 m long common power line connecting a switch to a light bulb

i. It is a distributed circuit.

ii. Time delay for propagation through it is negligible.

iii. It is in the form of a shielded coaxial cable of circular cross-section.

iv. As the intensity of the lamp varies, input impedance of this line also changes.

Which of the above statements is/are correct?

a) i only

b) i and ii

c) ii and iii

d) ii and iv

Ans: Option c)

59. With regard to a transmission line, which of the following statements is correct?

a) Any impedance repeats itself every λ/4 on the smith chart.

b) The S.W.R. = 2 circle and the magnitude of reflection coefficient = 0.5 circle coincide on the smith chart.

c) At any point on a transmission line, the current reflection coefficient is the reciprocal of the voltage reflection coefficient.

d) Matching eliminates the reflected wave between the source and the matching device location.

Ans: Option c)

60. It is required to match a 200 Ω load to a 450 Ω transmission line. To reduce the SWR along the line to 1, What must be the characteristic impedance of the quarter-wave transformer used for this purpose, if it is connected directly to the load?

a) 90 kΩ

b) 300 Ω

c) 9/4 Ω

d) 3/2 Ω

Ans: Option b)

61. The load end of a quarter wave transformer gets disconnected thereby causing an open-circuited load. What will be the input impedance of the transformer?

a) Zero

b) Infinite

c) Finite and positive

d) Finite and negative

Ans: Option a)

62. Multiple member of antennas are arranged in arrays in order to enhance what property?

a) Both directivity and bandwidth

b) Only directivity

c) Only bandwidth

d) Neither directivity nor bandwidth

Ans: Option b)

63. Consider the following statements regarding an antenna:

1. It is a transducer.

2. Its performance is essentially frequency sensitive.

3. It is a reciprocal device.

4. With increase in its effective aperture area, width of radiated beam increases.

Which of the above statements are correct?

a) 1,2 and 3

b) 1,2 and 4

c) 2 and 3 only

d) 1 and 4 only

Ans: Option a)

64.What is the minimum value of VSWR that may exist on a transmission line?

a) Less than zero

b) Zero

c) One

d) 10

Ans: Option c)

65. Assertion (A): Capacitance of a solid conducting spherical body of radius 'a' is given by 4πϵ₀a in free space.

Reason (R): ∇ x H = j ϵ 𝛚E + J

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 the correct explanation of A

c) A is true but R is false

d) A is false but R is true

Ans: Option b)

66. Assertion (A): The expression E = -∇V, Where E is the electric field and V is the potential is not valid for time varying fields.

Reason (R): The curl of a gradient is identically zero.

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 the correct explanation of A

c) A is true but R is false

d) A is false but R is true

Ans: Option b)

67.

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 the correct explanation of A

c) A is true but R is false

d) A is false but R is true

Ans: Option d)

68. Assertion (A): As the length of the resonant antenna is increased, the number of lobes increases and the direction of the major lobes is closer and closer to the direction of the dipole.

Reason (R): As the length increases, the current distribution along the wire becomes more and more uniform.

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 the correct explanation of A

c) A is true but R is false

d) A is false but R is true

Ans: Option c)

69. For a second order instrument, the optimum range of ξ(damping ratio), which gives good frequency response over a wide range of frequencies is
a) 0.5 to 0.6
b) 0.6 to 0.7
c) 0.7 to 0.8
d) 0.8 to 1.0

Ans: Option a)

70.The wheatstone bridge method of measuring resistance is ideally suited for the measurement of resistance values in the range of
a) 0.001 to 1 Ω
b) 0.1 to 100 Ω
c) 100 Ω to 10 kΩ
d) 100 kΩ to 10 MΩ

Ans: Option c)

71. What is the major cause of creeping in an energy-meter?
a) Over compensation for friction
b) Mechanical vibrations
c) Excessive voltage across the potential coil
d) Stray magnetic fields

Ans: Option a)

72. A compensated wattmeter has its reading corrected for error due to which one of the following parameters?
a) Frequency
b) Friction
c) Power consumed in current coil
d) power consumed in pressure coil

Ans: Option d)

73. Which of the following bridges is also used in an oscillator?
a) Maxwell
b) Schering
c) Hay
d) Wien

Ans: Option d)

74. Which of the following meters cannot measure a.c. quantities?
a) Thermocouple
b) Hot wire
c) P.M.M.C
d) Electrodynamometer

Ans: Option c)

75. Which of the following statements is not correct for thermistors?
a) They have negative temperature coefficient of resistance.
b) The sensing element is made of sintered ceramics, which are oxides of metals in the form of beads.
c) The variation of resistance with temperature is linear.
d) The resistance value at ambient temperature may range from 100 Ωto 100 k Ω.

Ans: Option c)

76. Which of the following devices is used at the first stage of an electronic voltmeter?
a) BJT
b) SCR
c) MOSFET
d) UJT

Ans: Option c)

77. Consider the following statements regarding sources of error in a Q-meter:
1. If a coil resistance R is connected in direct measurement mode and if the residual resistance of Q-meter is 0.1 R, then the measure Q of the coil would be 1.1 time the actual Q.
2. If the inductance to be measured is less than 0.1 mH, the error due to presence of residual inductance cannot be neglected.
3. The presence of distributed capacitance in a coil modifies the effective Q of the coil.
Which of the above statements are correct?
a) 1, 2 and 3
b) 1 and 2 only
c) 2 and 3 only
d) 1 and 3 only

Ans: Option c)

78. What is an advantage of an electronic voltmeter over a non-electronic voltmeter?
a) Low power consumption
b) Low input impedance
c) The ability to measure wide ranges of voltages and resistances
d) Large Portability

Ans: Option a)

79. An average response rectifier type electronic voltmeter has a d.c. voltage of 10 V applied to it. What is the meter reading?
a) 7.1 V
b) 10 V
c) 11.1 V
d) 22.2 V

Ans: Option c)

80. Which one of the following oscillators is used for the generation of high frequencies?
a) R-C phase shift oscillator
b) Wien bridge oscillator
c) L-C oscillator
d) Blocking oscillator

Ans: Option c)

81. Which of the following transducers requires a high input impedance pre-amplifier for proper measurements?
a)Thermocouple
b) Piezoelectric
c) Thermistor
d) L.V.D.T

Ans: Option b)

82. In a digital voltmeter the oscillator frequency is 400 kHz and the ramp voltage falls from 8 V to 0 V in 20 ms. What is the number of pulses counted by the counter?
a) 800
b) 2000
c) 4000
d) 8000

Ans: Option d)

83. Which of the following cannot provide as much time interval accuracy as the oscilloscope but can capture and display eight or more signals simultaneously, something that scopes cannot do?
a) Logical Analyzer
b) Digital Oscilloscope
c) Frequency Analyzer
d) Wave Analyzer

Ans: Option a)

84. Which of the following transducers is most suitable for monitoring continuous variations in very fine thickness of a material?
a) Diaphragm
b) Capacitor
c) L.V.D.T
d) Piezoelectric crystal

Ans: Option b)

85. Consider the following statements about ultrasonic flowmeters:
1. The measurement is insensitive to viscosity, pressure and temperature variations.
2. It has bidirectional measuring capability and can be used for any pipe size.
3. It has a relatively lower cost.
4. It has good accuracy, fast response and wide frequency range.

Which of the above statements is/are correct?
a) 1 only
b) 1 and 2 only
c) 1, 2 and 4
d) 3 and 4 only

Ans: Option c)

86.