Quiznetik

Electromagnetics | Set 2

1. The volume of a parallelepiped in Cartesian is

Correct : A. dv = dx dy dz

2. The scalar factor of Cartesian system is unity. State True/False.

Correct : A. true

3. The spherical equivalent of the vector B = yi + (x + z)j located at (-2,6,3) is given by

Correct : D. (7,64.62,-71.57)

4. Which of the following criteria is used to choose a coordinate system?

Correct : D. geometry

5. The cylindrical coordinate system is also referred to as

Correct : B. circular system

6. Transform the vector B=yi+(x+z)j located at point (-2,6,3) into cylindrical coordinates.

Correct : A. (6.325,-71.57,3)

7. Cylindrical systems have the following scalar values respectively

Correct : A. 1, ρ ,1

8. A charge located at point p (5,30⁰,2) is said to be in which coordinate system?

Correct : B. cylindrical system

9. Cylindrical system is employed in waveguides. State True/False.

Correct : A. true

10. The pressure inside a piston cylinder is a variable of

Correct : C. z plane distance

11. Charges filled inside a cylindrical will possess flux in which direction?

Correct : C. laterally outwards

12. Rectangular waveguides dominate the circular waveguides. Find the reason.

Correct : B. easy to design

13. Convert the point (3,4,5) from Cartesian to spherical coordinates

Correct : A. (7.07,45⁰,53⁰)

14. Example of spherical system in the following is

Correct : A. charge in space

15. Spherical systems are employed in waveguides. State True/False

Correct : B. false

16. Choose which of following condition is not required for a waveguide to exist.

Correct : C. the shape should be spherical

17. Find the spherical coordinates of A(2,3,-1)

Correct : B. (3.74, 105.5⁰, 56.31⁰)

18. Find the Cartesian coordinates of B(4,25⁰,120⁰)

Correct : B. (-0.845, 1.462, 3.625)

19. The area of sphere can be computed from the sphere volume. State True/False.

Correct : A. true

20. Given B= (10/r)i+( rcos θ) j+k in spherical coordinates. Find Cartesian points at (-3,4,0)

Correct : A. -2i + j

21. The scalar factor of spherical coordinates is

Correct : A. 1, r, r sin θ

22. The permittivity is also called

Correct : B. dielectric constant

23. Dielectric constant will be high in

Correct : C. insulators

24. Insulators perform which of the following functions?

Correct : C. provide electrical insulation

25. Find the susceptibility of a material whose dielectric constant is 2.26.

Correct : A. 1.26

26. The susceptibility of free space is

Correct : B. 0

27. When the electric field becomes zero, which of the following relations hold good?

Correct : B. d = p

28. Which of the following are conductors?

Correct : C. mercury

29. Find the range of band gap energy for conductors.

Correct : B. 0.2-0.4 ev

30. Conduction in metals is due to

Correct : A. electrons only

31. Find the band gap energy when a light of wavelength 1240nm is incident on it.

Correct : A. 1ev

32. Alternating current measured in a transmission line will be

Correct : C. rms value

33. The current in a metal at any frequency is due to

Correct : A. conduction current

34. For conductors, the free electrons will exist at

Correct : D. conduction band

35. The current flowing through an insulating medium is called

Correct : B. convection

36. Identify a good dielectric.

Correct : B. ceramics

37. A dielectric can be made a conductor by

Correct : B. heating

38. Find the dielectric constant for a material with electric susceptibility of 4.

Correct : B. 5

39. For a dielectric which of the following properties hold good?

Correct : B. they are superconductors at low temperatures

40. he magnetic field which destroys the superconductivity is called

Correct : D. critical field

41. The magnetic susceptibility in a superconductor will be

Correct : B. negative

42. The superconducting materials will be independent of which of the following?

Correct : B. electric field

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

Correct : B. 36

44. The best definition of polarisation is

Correct : B. electric dipole moment per unit volume

45. Polarizability is defined as the

Correct : B. ratio of dipole moment to electric field

46. Identify which type of polarisation depends on temperature.

Correct : C. orientational

47. The total polarisation of a material is the

Correct : B. sum of all types of polarisation

48. In the given types of polarisation, which type exists in the semiconductor?

Correct : D. interfacial or space charge

49. Solids do not have which type of polarisation?

Correct : C. interfacial

50. Which of the following is not an example of elemental solid dielectric?

Correct : C. silicon

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

Correct : B. 16

52. Curie-Weiss law is applicable to which of the following materials?

Correct : B. ferroelectric

53. Curie-Weiss law is used to calculate which one of the following?

Correct : C. electric susceptibility

54. Calculate the loss tangent when the dielectric constant in AC field is given by 3 + 2j.

Correct : D. (-2/3)

55. When a dielectric loses its dielectric property, the phenomenon is called

Correct : B. dielectric breakdown

56. Choose the best definition of dielectric loss.

Correct : A. absorption of electric energy by dielectric in an ac field

57. The charge within a conductor will be

Correct : C. 0

58. For a conservative field which of the following equations holds good?

Correct : A. ∫ e.dl = 0

59. Find the electric field if the surface density at the boundary of air is 10-9.

Correct : C. 36π

60. Find the flux density at the boundary when the charge density is given by 24 units.

Correct : B. 24

61. The normal component of which quantity is always discontinuous at the boundary?

Correct : B. d

62. 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

63. In free space, the Poisson equation becomes

Correct : C. laplace equation

64. If Laplace equation satisfies, then which of the following statements will be true?

Correct : B. current will be infinite

65. Suppose the potential function is a step function. The equation that gets satisfied is

Correct : A. laplace equation

66. The function V = exsin y + z does not satisfy Laplace equation. State True/False.

Correct : B. false

67. Poisson equation can be derived from which of the following equations?

Correct : A. point form of gauss law

68. Find the charge density from the function of flux density given by 12x – 7z.

Correct : C. 5

69. Find the electric field of a potential function given by 20 log x + y at the point (1,1,0).

Correct : A. -20 i – j

70. When a material has zero permittivity, the maximum potential that it can possess is

Correct : D. zero

71. Work done in charging a capacitor is

Correct : B. 1⁄2qv

72. Energy stored in 2000mF capacitor charged to a potential difference of 10V is?

Correct : A. 100j

73. When do we get maximum energy from a set of capacitors?

Correct : A. when they are connected in parallel

74. Calculate the energy in the 2F capacitor.

Correct : D. 6.4kj

75. Calculate the energy in the 4F capacitor.

Correct : C. 12.8kj

76. Calculate the energy stored in the combination of the capacitors.

Correct : C. 19.2kj

77. The unit for dielectric strength is

Correct : C. mv/m

78. If the Voltage increases, what happens to dielectric strength?

Correct : A. increases

79. If the thickness of the material increases, what happens to the dielectric strength?

Correct : B. decreases

80. Which medium has the highest dielectric strength?

Correct : C. air

81. Leakage in capacitors is primarily caused by

Correct : A. transistors

82. What is the conduction current when a capacitor is fully charged?

Correct : B. zero

83. The flow of electrons in dielectric is due to

Correct : C. breakdown

84. The flow of electrons which does not pass through the battery is known as

Correct : A. displacement current

85. The free electrons in practical dielectrics is due to _

Correct : C. impurities

86. What is the type of current where the electrons actually move?

Correct : B. conduction current

87. What is the type of current caused due to variations in the field?

Correct : A. displacement current

88. Under normal conditions capacitors have _

Correct : A. displacement current

89. Under normal conditions capacitors have _

Correct : A. displacement current

90. What is the unit for displacement current?

Correct : B. ampere

91. Displacement current depends on _

Correct : B. change in time

92. Magnetic fields between the parallel plates of a capacitor are due to?

Correct : A. displacement current

93. The free electrons in practical dielectrics are due to

Correct : C. impurities

94. Paper capacitor is a type of _

Correct : A. fixed capacitor

95. A capacitor using chemical reactions to store charge is _

Correct : D. electrolyte capacitor

96. Which, among the following, is the odd one out?

Correct : C. tuning capacitor

97. In a variable capacitor, capacitance can be varied by

Correct : A. turning the rotatable plates in or out

98. The simplest kind of capacitor is _

Correct : D. paper capacitor

99. Capacitor preferred when there is high frequency in the circuits is _

Correct : B. mica capacitor

100. The type of capacitors used in communication transmitters are?

Correct : B. variable capacitor