Quiznetik

Electromagnetics | Set 6

1. The power of the electromagnetic wave with electric and magnetic field intensities given by 12 and 15 respectively is

Correct : B. 90

2. The transmission coefficient is given by 0.65. Find the return loss of the wave.

Correct : A. 9.11

3. The intrinsic impedance of a wave with electric and magnetic field of 10 and 8 respectively is

Correct : B. 1.11

4. The intrinsic impedance in free space is

Correct : D. 120π

5. The skin effect is a phenomenon observed in

Correct : C. conductors

6. The skin depth is measured in

Correct : D. micrometer

7. The attenuation constant is 0.5 units. The skin depth will be

Correct : C. 2

8. The relation between the skin depth and frequency is given by

Correct : D. skin depth α 1/√f

9. The skin depth of the wave having a frequency of 3MHz and a velocity of 12 m/s is

Correct : C. 4

10. The coaxial cable consists of

Correct : D. two conductors with dielectric

11. The transmission line is said to be lossless when the

Correct : A. conductor is perfect and dielectric is lossless

12. The resistance of a lossless transmission line is

Correct : A. 0

13. The attenuation constant is measured in the units of

Correct : B. neper

14. The condition that holds good in a distortionless transmission line is

Correct : A. r/l = g/c

15. Given that R = 20 ohm, L = 40 mH, C = 40 μF, G = 0.02 mho. Find whether the line is distortionless or not.

Correct : B. distortionless line

16. For R= 20 ohm and G= 0.8 mho, the attenuation constant will be

Correct : A. 16

17. The Smith chart is a polar chart which plots

Correct : B. r vs znorm

18. The Smith chart consists of the

Correct : C. constant r and constant x circles

19. The circles in the Smith chart pass through which point?

Correct : D. (1,0)

20. Moving towards the clockwise direction in the Smith chart implies moving

Correct : A. towards generator

21. The centre of the point having a normalised resistance of 1.2 ohm and reactance of 1.5 ohm is

Correct : A. (0.54,0)

22. The normalised load impedance of the transmission line 50 ohm with a load of 30 ohm is

Correct : D. 3/5

23. The radius of the point having a normalised resistance of 1 ohm is

Correct : C. 0.5

24. The open circuit line will have a reflection coefficient of

Correct : B. 1

25. For time varying currents, the field or waves will be

Correct : C. electromagnetic

26. According to Faraday’s law, EMF stands for

Correct : D. electromotive force

27. Find the displacement current when the flux density is given by t3 at 2 seconds.

Correct : C. 12

28. Find the force due to a current element of length 2cm and flux density of 12 tesla. The current through the element will be 5A.

Correct : B. 1.2 n

29. When the conduction current density and displacement current density are same, the dissipation factor will be

Correct : D. unity

30. The divergence of which quantity will be zero?

Correct : D. b

31. Find the charge density when the electric flux density is given by 2x i + 3y j + 4z k.

Correct : B. 9

32. Find the Maxwell equation derived from Faraday’s law.

Correct : C. curl(e) = -db/dt

33. Find the Maxwell law derived from Ampere law.

Correct : C. curl(h) = j

34. In which of the following forms can Maxwell’s equation not be represented?

Correct : A. static

35. The charge build up in the capacitor is due to which quantity?

Correct : B. displacement current

36. In metals which of the following equation will hold good?

Correct : A. curl(h) = j

37. Find the flux enclosed by a material of flux density 12 units in an area of 80cm.

Correct : A. 9.6

38. Find the electric flux density of a material with charge density 16 units in unit volume.

Correct : C. 16

39. Find the conductivity of a material with conduction current density 100 units and electric field of 4 units.

Correct : A. 25

40. Calculate the displacement current density when the electric flux density is 20sin 0.5t.

Correct : B. 10cos 0.5t

41. The power of the electromagnetic wave with electric and magnetic field intensities given by 12 and 15 respectively is

Correct : B. 90

42. The power of a wave of with voltage of 140V and a characteristic impedance of 50 ohm is

Correct : C. 196

43. The power reflected by a wave with incident power of 16 units is(Given that the reflection coefficient is 0.5)

Correct : D. 4

44. The incident and the reflected voltage are given by 15 and 5 respectively. The transmission coefficient is

Correct : B. 2/3

45. The current reflection coefficient is given by -0.75. Find the voltage reflection coefficient.

Correct : D. 0.75

46. The attenuation is given by 20 units. Find the power loss in decibels.

Correct : A. 13.01

47. The curl of the electric field intensity is

Correct : B. rotational

48. Which of the following identities is always zero for static fields?

Correct : D. curl(grad v)

49. Find the displacement current density of a material with flux density of 5sin t

Correct : C. 5cos t

50. Find the magnetic field intensity when the magnetic vector potential x i + 2y j + 3z k.

Correct : B. -6

51. The value of ∫ H.dL will be

Correct : B. i

52. Given the vector potential is 16 – 12sin y j. Find the field intensity at the origin.

Correct : C. 12

53. The Laplacian of the magnetic vector potential will be

Correct : A. –μ j

54. Find the gradient of t = x2y+ ez at the point p(1,5,-2)

Correct : B. 10i + j + 0.135k

55. + z2 at (1,1,1)

Correct : B. 2i + 2j + 2k

56. i + 2xy j + 5xz2 k

Correct : D. √4.04

57. ,2,5) is (in Joule)

Correct : B. 0.72

58. /x) j + 5 k.

Correct : C. -8.214

59. πε) ln(b/a). State True/False.

Correct : A. true

60. i in spherical coordinates with r = 4m and θ = π/2.

Correct : C. 588.9

61. and 1, y = 0 and 2, z = 0 and 3.

Correct : B. 12

62. in volume integral.

Correct : C. 75 π

63. , hence find charge using volume integral.

Correct : D. 6400 π

64. j.

Correct : C. 80/3

65. = 9.

Correct : B. 180π

66. 5cm apart in transformer oil(εr=2.2) in 10-4 N,

Correct : D. 1.815

67. 5 X 10-7 C, both the charges are in vacuum.

Correct : D. 0.09

68. cm in vacuum(in 10-8C)

Correct : A. 4

69. cm and minimises as d increases. State True/False

Correct : A. true

70. Electric field of an infinitely long conductor of charge density λ, is given by E =λ/(2πεh).aN. State True/False

Correct : A. true

71. ,1,1)m?

Correct : B. -10-6

72. 14 units?

Correct : D. 0.25

73. Find the potential of V = 60sin θ/r2 at P(3,60,25)

Correct : A. 5.774

74. ,1,3).

Correct : B. 106

75. What is the potential difference between 10sinθcosφ/r2 at A(1,30,20) and B(4,90,60)?

Correct : C. 4.386

76. m from the ring.

Correct : D. 72π

77. at R = 4m and σ = -3 at R = 5m. Find the flux density at R = 1m.

Correct : A. 0

78. at R = 4m and σ = -3 at R = 5m. Find the flux density at R = 3m.

Correct : B. 10/3

79. at R = 4m and σ =-3 at R = 5m. Find the flux density at R = 4.5m.

Correct : C. 2/4.5

80. at R = 4m and σ = -3 at R = 5m. Find the flux density at R = 6m.

Correct : D. -13/6

81. Find the electric potential for an electric field 3units at a distance of 2m.

Correct : C. 6

82. Find the potential at a point (4, 3, -6) for the function V = 2x2y + 5z.

Correct : B. 66

83. -10 units)

Correct : C. 2.5

84. Transform the vector A = 3i – 2j – 4k at P(2,3,3) to cylindrical coordinates

Correct : A. -3.6j – 4k

85. , -2)

Correct : A. 2.467i + j + 1.167k

86. Transform the vector (4,-2,-4) at (1,2,3) into spherical coordinates.

Correct : B. -3.197i + 2.393j – 4.472k

87. units.

Correct : C. 1000

88. m/s.

Correct : B. 2400

89. Find the mean free path of an electron travelling at a speed of 18m/s in 2 seconds.

Correct : B. 36

90. units.

Correct : A. 200

91. units and E = 8 units.

Correct : C. 36

92. units.

Correct : C. 60

93. Compute the refractive index when the dielectric constant is 256 in air.

Correct : B. 16

94. Find the permittivity of the surface when a wave incident at an angle 60 is reflected by the surface at 45 in air

Correct : D. 1.73

95. Calculate the energy in the 4F capacitor.

Correct : C. 12.8kj

96. kV.

Correct : C. 0.035n

97. kV. Find „a‟.

Correct : D. 1mm

98. kV. Find „a‟.

Correct : D. 1000cm

99. The unit for dielectric strength is ____________

Correct : C. mv/m

100. m, calculate the dielectric strength.

Correct : A. 2mv/m