EE8391 Electromagnetic Theory multiple choice/one mark questions and answers - Anna University

EE8391 Electromagnetic Theory Questions and Answers

(Regulation 2017 Anna University) 

Prepared by Mr.D.Navin Sam,Assistant Professor, Dept of EEE, Karpagam Institute of Technology, Coimbatore

UNIT I ELECTROSTATICS – I

Sources and effects of electromagnetic fields – Coordinate Systems – Vector fields –Gradient, Divergence, Curl – theorems and applications – Coulomb’s Law – Electric field intensity – Field due to discrete and continuous charges – Gauss’s law and applications.  

1.       Lorentz force is based on,

a)  Dot product

b)  Cross product

c)  Both dot and cross product

d)  Independent of both

2.       The cross product of the vectors 3i + 4j – 5k and –i + j – 2k is,

a)  3i – 11j + 7k

b)  -3i + 11j + 7k

c)  -3i – 11j – 7k

d)  -3i + 11j – 7k

3.       The del operator is called as

a)  Gradient

b)  Curl

c)  Divergence

d)  Vector differential operator

4.       A vector is said to be solenoidal when its

a)  Divergence is zero

b)  Divergence is unity

c)  Curl is zero

d)  Curl is unity

5.       The magnetic field intensity is said to be

a)  Divergent

b)  Curl free

c)  Solenoidal

d)  Rotational

6.       A field has zero divergence and it has curls. The field is said to be

a)  Divergent, rotational

b)  Solenoidal, rotational

c)  Solenoidal, irrotational

d)  Divergent, irrotational

7.       When a vector is irrotational, which condition holds good?

a)  Stoke’s theorem gives non-zero value

b)  Stoke’s theorem gives zero value

c)  Divergence theorem is invalid

d)  Divergence theorem is valid

8.       The Cartesian system is also called as

a)  Circular coordinate system

b)  Rectangular coordinate system

c)  Spherical coordinate system

d)  Space coordinate system

9.       The volume of a parallelepiped in Cartesian is

a)  dV = dx dy dz

b)  dV = dx dy

c)  dV = dy dz

d)  dV = dx dz

10.   The angular separation between the vectors A = 4i + 3j + 5k and B = i – 2j + 2k is (in degrees) a) 65.8

b)  66.8

c)  67.8

d)  68.8

11.   Transform the vector A = 3i – 2j – 4k at P(2,3,3) to cylindrical coordinates a) -3.6j – 4k

b)  -3.6j + 4k

c)  3.6j – 4k

d)  3.6j + 4k

12.   The cylindrical coordinate system is also referred to as

a)  Cartesian system

b)  Circular system

c)  Spherical system

d)  Space system

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

a)  True

b)  False

14.   Convert the given rectangular coordinates A(2,3,1) into corresponding cylindrical coordinates

a)  (3.21,56.31,1)

b)  (3.21,57.31,0)

c)  (3.61,57.31,0)

d)  (3.61,56.31,1)

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

a)  (7.07,45,53)

b)  (0.707,45,53 )

c)  (7.07,54,63)

d)  (0.707,54,63⁰)

16.   Example of spherical system in the following is

a)  Charge in space

b)  Charge in box

c)  Charge in dielectric

d)  Uncharged system

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

a)  (3.74, 105.5, 56.13)

b)  (3.74, 105.5, 56.31)

c)  (3.74, 106.5, 56.13)

d)  (3.74, 106.5, 56.31⁰)

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

a)  3.197i – 2.393j + 4.472k

b)  -3.197i + 2.393j – 4.472k

c)  3.197i + 2.393j + 4.472k

d)  -3.197i – 2.393j – 4.472k

19.   The gradient of xi + yj + zk is

a)  0

b)  1

c)  2

d)  3

20.   The divergence of a vector is a scalar. State True/False.

a)  True

b)  False

21.   Compute the divergence of the vector xi + yj + zk.

a)  0

b)  1

c)  2

d)  3

22.   Find the divergence of the vector yi + zj + xk.

a)  -1

b)  0

c)  1

d)  3

23.   Find whether the vector is solenoidal, E = yz i + xz j + xy k

a)  Yes, solenoidal

b)  No, non-solenoidal

c)  Solenoidal with negative divergence

d)  Variable divergence

24.   Find the divergence of the field, P = x²yz i + xz k

a)  xyz + 2x

b)  2xyz + x

c)  xyz + 2z

d)  2xyz + z

25.   Identify the nature of the field, if the divergence is zero and curl is also zero.

a)  Solenoidal, irrotational

b)  Divergent, rotational

c)  Solenoidal, irrotational

d)  Divergent, rotational

26.   Which of the following theorem use the curl operation?

a)  Green’s theorem

b)  Gauss Divergence theorem

c)  Stoke’s theorem

d)  Maxwell equation

27.   . Is the vector is irrotational. E = yz i + xz j + xy k

a)  Yes

b)  No

28.   Find the curl of the vector A = yz i + 4xy j + y k

a)  xi + j + (4y – z)k

b)  xi + yj + (z – 4y)k

c)  i + j + (4y – z)k

d)  i + yj + (4y – z)k

29.   Which of the following Maxwell equations use curl operation?

a)  Maxwell 1st and 2nd equation

b)  Maxwell 3rd and 4th equation

c)  All the four equations

d)  None of the equations

30.   The integral form of potential and field relation is given by line integral. State True/False a) True

b) False

31.   If V = 2x²y – 5z, find its electric field at point (-4,3,6)

a)  47.905

b)  57.905

c)  67.905

d)  77.905

32.   Find the potential between two points p(1,-1,0) and q(2,1,3) with E = 40xy i + 20x² j + 2 k a) 104

b)  105

c)  106

d)  107

33.   A field in which a test charge around any closed surface in static path is zero is called a) Solenoidal

b)  Rotational

c)  Irrotational

d)  Conservative

34.   The potential in a lamellar field is

a)  1

b)  0

c)  -1

d)  ∞

35.   Line integral is used to calculate

a)  Force

b)  Area

c)  Volume

d)  Length

36.   The energy stored in the inductor 100mH with a current of 2A is a) 0.2

b)  0.4

c)  0.6

d)  0.8

37.   Gauss law for electric field uses surface integral. State True/False

a)  True

b)  False

38.   Surface integral is used to compute

a)  Surface

b)  Area

c)  Volume

d)  density

39.   Evaluate Gauss law for D = 5r²/4 i in spherical coordinates with r = 4m and θ = π/2. a) 600

b)  599.8

c)  588.9

d)  577.8

40.   The divergence theorem converts

a)  Line to surface integral

b)  Surface to volume integral

c)  Volume to line integral

d)  Surface to line integral

41.   The triple integral is used to compute volume. State True/False

a)  True

b)  False

42.   Find the charged enclosed by a sphere of charge density ρ and radius a. a) ρ (4πa²)

b)  ρ(4πa³/3)

c)  ρ(2πa²)

d)  ρ(2πa³/3)

43.   The point form of Gauss law is given by, Div(V) = ρv State True/False.

a)  True

b) False

44.   The Poisson equation cannot be determined from Laplace equation. State True/False. a) True

b) False

45.   Given the potential V = 25 sin θ, in free space, determine whether V satisfies Laplace’s equation. a) Yes

b)  No

c)  Data sufficient

d)  Potential is not defined

46.   Find the Laplace equation value of the following potential field V = x² – y² + z² a) 0

b)  2

c)  4

d)  6

47.   When a potential satisfies Laplace equation, then it is said to be

a)  Solenoidal

b)  Divergent

c)  Lamellar

d)  Harmonic

48.   The Stoke’s theorem uses which of the following operation?

a)  Divergence

b)  Gradient

c)  Curl

d)  Laplacian

49.   The voltage of a capacitor 12F with a rating of 2J energy is

a)  0.57

b) 5.7

c)  57

d) 570

50.   Find the force between 2C and -1C separated by a distance 1m in air(in newton). a) 18 X 10⁶

b)  -18 X 10⁶

c)  18 X 10^-6

d)  -18 X 10^-6

51.   Two charges 1C and -4C exists in air. What is the direction of force?

a)  Away from 1C

b)  Away from -4C

c)  From 1C to -4C

d)  From -4C to 1C

 

UNIT II ELECTROSTATICS – II

 Electric potential – Electric field and equipotential plots, Uniform and Non-Uniform field, Utilization factor – Electric field in free space, conductors, dielectrics – Dielectric polarization – Dielectric strength – Electric field in multiple dielectrics – Boundary conditions, Poisson’s and Laplace’s equations, Capacitance, Energy density, Applications.

 

1.       The electric field intensity is defined as

a)  Force per unit charge

b)  Force on a test charge

c)  Force per unit charge on a test charge

d)  Product of force and charge

2.       Find the force on a charge 2C in a field 1V/m.

a)  0

b)  1

c)  2

d)  3

3.       Electric field intensity due to infinite sheet of charge σ is

a)  Zero

b)  Unity

c)  σ/ε

d)  σ/2ε

4.       In electromagnetic waves, the electric field will be perpendicular to which of the following?

a)  Magnetic field intensity

b)  Wave propagation

c)  Both H and wave direction

d)  It propagates independently

5.       The Gaussian surface is

a)  Real boundary

b)  Imaginary surface

c)  Tangential

d)  Normal

6.       If the radius of a sphere is 1/(4π)m and the electric flux density is 16π units, the total flux is given by, a) 2

b)  3

c)  4

d)  5

7.       A point charge 2nC is located at origin. What is the potential at (1,0,0)? a) 12

b)  14

c)  16

d)  18

8.         A point charge 0.4nC is located at (2, 3, 3). Find the potential differences between (2, 3, 3)m and (-2, 3, 3)m due to the charge. a) 2.5

b)  2.6

c)  2.7

d)  2.8

9.         Given E = 40xyi + 20x²j + 2k. Calculate the potential between two points (1,-1,0) and (2,1,3). a) 105

b)  106

c)  107

d)  108

10.     The potential difference in an open circuit is

a)  Zero

b)  Unity

c)  Infinity

d)  Circuit does not exist open

11.     The potential taken between two points across a resistor will be

a)  Positive

b)  Negative

c)  Zero

d)  Infinity

12.     The voltage at any point in an ac circuit will be

a)  Peak voltage

b)  RMS voltage

c)  Average voltage

d)  Source voltage

13.     The electric flux density and electric field intensity have which of the following relation? a) Linear

b)  Nonlinear

c)  Inversely linear

d)  Inversely nonlinear

14.     The electric field intensity is the negative gradient of the electric potential. State True/False. a) True

b)  False

15.     Find the potential at a point (4, 3, -6) for the function V = 2x²y + 5z. a) 96

b)  66

c)  30

d)  -66

16.     Find the potential of the function V = 60cos θ/r at the point P(3, 60, 25). a) 20

b)  10

c)  30

d)  60

17.     Find the work done moving a charge 2C having potential V = 24volts is a) 96

b)  24

c)  36

d)  48

18.     Calculate the capacitance of a material in air with area 20 units and distance between plates is 5m. a) 35.36pF

b)  3.536pF

c)  35.36nF

d)  3.536nF

19.     Find the current density of a material with resistivity 20 units and electric field intensity 2000 units. a) 400

b)  300

c)  200

d)  100

20.     In electric fields, D= ε E. The correct expression which is analogous in magnetic fields will be

a)  H = μ B

b)  B = μ H

c)  A = μ B

d)  H = μ A

21.     Compute the power consumed by a material with current density 15 units in an area of 100 units. The potential measured across the material is 20V. a) 100kJ

b)  250kJ

c)  30kJ

d)  15kJ

22.     The potential due to a dipole at a point P from it is the

a)  Sum of potentials at the charges

b)  Difference of potentials at the charges

c)  Multiplication of potentials at the charges

d)  Ratio of potentials at the charges

23.     For two charges 3C and -3C separated by 1cm and are located at distances 5cm and 7cm respectively from the point P, then the distance between their midpoint and the point P will be

a)  5.91

b) 12.6

c)  2

d) 9

24.     The potential due to the dipole on the midpoint of the two charges will be a) 0

b)  Unity

c)  ∞

d)  -∞

25.     Dipoles in any electric field undergo

a)  Magnetism

b)  Electromagnetism

c)  Magnetisation

d)  Polarisation

26.     The electrostatic energy in an electric field does not depend on which of the following? a) Magnitude of charges

b)  Permittivity

c)  Applied electric field

d)  Flux lines

27.     Calculate the energy in an electric field with flux density 6 units and field intensity of 4 units. a) 12

b)  24

c)  36

d)  48

28.     Equipotential surface is a

a)  Real surface

b)  Complex surface

c)  Imaginary surface

d)  Not existing surface

29.     The work done in moving a test charge from one point to another in an equipotential surface is zero. State True/False. a) True

b)  False

30.     The permittivity is also called

a)  Electrostatic energy

b)  Dielectric constant

c)  Dipole moment

d)  Susceptibility

31.     Dielectric constant will be high in

a)  Conductors

b)  Semiconductors

c)  Insulators

d)  Superconductors

32.     Semiconductors possess which type of bonding?

a)  Metallic

b)  Covalent

c)  Ionic

d)  Magnetic

33.     The susceptibility of free space is

a)  1

b)  0

c)  2

d)  ∞

34.     When the electric field becomes zero, which of the following relations hold good? a) E = P

b)  D = P

c)  B = P

d)  H = P

35.     For conductors, the free electrons will exist at

a)  Valence band

b)  Middle of valence and conduction band

c)  Will not exist

d)  Conduction band

36.     Find the conduction current density when conductivity of a material is 500 units and corresponding electric field is 2 units. a) 500

b)  250

c)  1000

d)  2000

37.     A dielectric is always an insulator. But an insulator is not necessarily a dielectric. State True/False. a) True

b)  False

38.     Find the dielectric constant for a material with electric susceptibility of 4. a) 3

b)  5

c)  8

d)  16

39.     The ratio of conduction to displacement current density is referred to as

a)  Attenuation constant

b)  Propagation constant

c)  Loss tangent

d)  Dielectric constant

40.     In good conductors, the electric and magnetic fields will be

a)  45 in phase

b)  45 out of phase

c)  90 in phase

d)  90 out of phase

41.     In free space, which of the following will be zero?

a)  Permittivity

b)  Permeability

c)  Conductivity

d)  Resistivity

42.     The intrinsic impedance of free space is given by

a)  272 ohm

b)  412 ohm

c)  740 ohm

d)  377 ohm

43.     Calculate the energy stored per unit volume in a dielectric medium due to polarisation when P = 9 units and E = 8 units. a) 1.77

b)  2.25

c)  36

d)  144

44.     The charge within a conductor will be

a)  1

b)  -1

c)  0

d)  ∞

45.     For a conservative field which of the following equations holds good? a) ∫ E.dl = 0

b)  ∫ H.dl = 0

c)  ∫ B.dl = 0

d)  ∫ D.dl = 0

46.     Which component of the electric field intensity is always continuous at the boundary? a) Tangential

b)  Normal

c)  Horizontal

d)  Vertical

47.     Find the permittivity of the surface when a wave incident at an angle 60 is reflected by the surface at 45 in air. a) 1.41

b)  3.5

c)  2.2

d)  1.73

48.     Find the capacitance when charge is 20 C has a voltage of 1.2V.

a)  32.67

b)  16.67

c)  6.67

d)  12.33

49.     Calculate the capacitance of two parallel plates of area 2 units separated by a distance of 0.2m in air(in picofarad) a) 8.84

b)  88.4

c)  884.1

d)  0.884

50.     Compute the capacitance between two concentric shells of inner radius 2m and the outer radius is infinitely large. a) 0.111 nF

b)  0.222 nF

c)  4.5 nF

d)  5.4 nF

 

 UNIT III MAGNETOSTATICS

 Lorentz force, magnetic field intensity (H) – Biot–Savart’s Law – Ampere’s Circuit Law – H due to straight conductors, circular loop, infinite sheet of current, Magnetic flux density (B) – B in free space, conductor, magnetic materials – Magnetization, Magnetic field in multiple media – Boundary conditions,   scalar   and         vector potential,         Poisson’s         Equation,        Magnetic         force,   Torque, Inductance, Energy density, Applications.

1.       Which of the following cannot be computed using the Biot Savart law?

a)  Magnetic field intensity

b)  Magnetic flux density

c)  Electric field intensity

d)  Permeability

2.       Find the magnetic field of a finite current element with 2A current and height 1/2π is a) 1

b)  2

c)  1/2

d)  ¼

3.       Calculate the magnetic field at a point on the centre of the circular conductor of radius 2m with current 8A. a) 1

b)  2

c)  3

d)  4

4.       The current element of the solenoid of turns 100, length 2m and current 0.5A is given by, a) 100 dx

b)  200 dx

c)  25 dx

d)  50 dx

5.       Find the magnetic field intensity at the centre O of a square of the sides equal to 5m and carrying 10A of current. a) 1.2

b)  1

c)  1.6

d)  1.8

6.       Find the magnetic flux density when a point from a finite current length element of current 0.5A and radius 100nm. a) 0

b)  0.5

c)  1

d)  2

7.       The magnetic field intensity will be zero inside a conductor. State true/false. a) True

b)  False

8.       The point form of Ampere law is given by

a)  Curl(B) = I

b)  Curl(D) = J

c)  Curl(V) = I

d)  Curl(H) = J

9.       The Ampere law is based on which theorem?

a)  Green’s theorem

b)  Gauss divergence theorem

c)  Stoke’s theorem

d)  Maxwell theorem

10.   Calculate the magnetic field intensity due to a toroid of turns 50, current 2A and radius 159mm.

a)  50

b)  75

c)  100

d)  200

11.   Find the magnetic field intensity due to an infinite sheet of current 5A and charge density of 12j units in the positive y direction and the z component is below the sheet. a) 6

b)  0

c)  -6

d)  60k

12.   The H quantity is analogous to which component in the following? a) B

b)  D

c)  E

d)  V

13.   The magnetic flux density is directly proportional to the magnetic field intensity. State True/False. a) True

b)  False

14.   Ampere law states that,

a)  Divergence of H is same as the flux

b)  Curl of D is same as the current

c)  Divergence of E is zero

d)  Curl of H is same as the current density

15.   Find the magnetic field intensity due to a solenoid of length 12cm having 30 turns and current of 1.5A. a) 250

b)  325

c)  175

d)  375

16.   Find the magnetic field intensity at the radius of 6cm of a coaxial cable with inner and outer radii are 1.5cm and 4cm respectively. The current flowing is 2A. a) 2.73

b)  3.5

c)  0

d)  1.25

17.   Find the magnetic field intensity of a toroid of turns 40 and radius 20cm. The current carried by the toroid be 3.25A. a) 103.45

b)  102

c)  105.7

d)  171

18.   Find the magnetic field intensity when the flux density is 8 x 10^-6 Tesla in the medium of air.

a)  6.36

b) 3.66

c)  6.63

d) 3.36

19.   Find the magnetic flux density of the material with magnetic vector potential A = y i + z j + x k.

a)  i + j + k

b)  –i – j – k

c)  –i-j

d)  –i-k

20.   Find the magnetic flux density when a flux of 28 units is enclosed in an area of 15cm. a) 178.33

b)  186.67

c)  192.67

d)  124.33

21.   Find current density J when B = 50 x 10-6 units and area dS is 4 units. a) 9.94

b)  8.97

c)  7.92

d)  10.21

22.   Find the magnetic field intensity when the magnetic vector potential x i + 2y j + 3z k. a) 6

b)  -6

c)  0

d)  1

23.   Given the vector potential is 16 – 12sin y j. Find the field intensity at the origin. a) 28

b)  16

c)  12

d)  4

24.   The Laplacian of the magnetic vector potential will be

a)  –μ J

b) – μ I

c)  –μ B

d) –μ H

25.   The relation between flux density and vector potential is

a)  B = Curl(A)

b) A = Curl(B)

c)  B = Div(A)

d) A = Div(B)

26.   Find the induced EMF in an inductor of 2mH and the current rate is 2000 units. a) 4

b)  -4

c)  1

d)  -1

27.   Find the inductance of a material with 100 turns, area 12 units and current of 2A in air. a) 0.75mH

b)  7.5mH

c)  75mH

d)  753mH

28.   Calculate the magnetic energy when the magnetic flux density is given by 32 units(in 10⁸ order) a) 4.07

b)  7.4

c)  0.47

d)  7.04

29.   Find the inductance when the energy is given by 2 units with a current of 16A. a) 15.6mH

b)  16.5mH

c)  16.8mH

d)  15.8mH

30.   Find the turns in an solenoid of inductance 23.4mH , current 2A and area 15cm. a) 900

b)  400

c)  498

d)  658

31.   The inductance is the measure of

a)  Electric charges stored by the material

b)  Emf generated by energising the coil

c)  Magnetic field stored by the material

d)  Magnetization of dipoles

32.   Find the total flux in a coil of magnetic flux density 12 units and area 7 units. a) 0.84

b)  0.96

c)  8.4

d)  9.6

33.   Which of the following relation will hold good?

a)  D = μ H

b)  B = ε E

c)  E = ε D

d)  B = μ H

34.   Find the force experienced by an electromagnetic wave in a conductor?

a)  Electrostatic force

b)  Magneto static force

c)  Electro motive force

d)  Lorentz force

35.   Identify the devices that do not use electromagnetic energy.

a)  Television

b)  Washing machine

c)  Microwave oven

d)  Mobile phones

36.   Which type of flux will increase the inductance?

a)  Series aiding

b) Series opposing

c)  Shunt aiding

d) Shunt opposing

37.   Find the Lorentz force of a charge 2.5C having an electric field of 5 units and magnetic field of 7.25 units with a velocity 1.5m/s. a) 39.68

b)  68.39

c)  86.93

d)  93.68

38.   When currents are moving in the same direction in two conductors, then the force will be a) Attractive

b)  Repulsive

c)  Retracting

d)  Opposing

39.   Find the torque in a conductor having current 2A, flux density 50 units, length 15cm and distance of 8m. a) 120

b)  240

c)  800

d)  350

40.   Find the angle at which the torque is minimum.

a)  30

b)  45

c)  60

d)  90

41.   Calculate the magnetic moment when a field of B= 51 units is subjected to a torque of 20 units.

a)  0.39

b) 4.2

c)  2.55

d) 3.21

42.   The torque expression of a current carrying conductor is

a)  T = BIA cos θ

b)  T = BA cos θ

c)  T = BIA sin θ

d)  T = BA sin θ

43.   The tangential component of the magnetic field intensity is continuous at the boundary of separation of two media. State True/False. a) True

b)  False

44.   The line integral of the magnetic field intensity is the

a)  Current density

b)  Current

c)  Magnetic flux density

d)  Magnetic moment

45.   A boundary of separation between two magnetic materials is identified by which factor?

a)  Change in the permeability

b) Change in permittivity

c)  Change in magnetization

d) Conduction

46.   Calculate the emf of a coil with turns 100 and flux rate 5 units. a) 20

b)  -20

c)  500

d)  -500

47.   The expression for the inductance in terms of turns, flux and current is given by a) L = N dφ/di

b)  L = -N dφ/di

c)  L = Niφ

d)  L = Nφ/i

48.   A coil is said to be loosely coupled with which of the following conditions? a) K>1

b)  K<1

c)  K>0.5

d)  K<0.5

49.   With unity coupling, the mutual inductance will be

a)  L1 x L2

b)  L1/L2

c)  √(L1 x L2)

d)  L2/L1

50.   The inductance of a coaxial cable with inner radius a and outer radius b, from a distance d, is given by

a)  L = μd ln(b/a)/2π

b) L = 2π μd ln(b/a)

c)  L = πd/ln(b/a)

d) L = 0

 

UNIT IV ELECTRODYNAMIC FIELDS

Magnetic Circuits – Faraday’s law – Transformer and motional EMF – Displacement current – Maxwell’s equations (differential and integral form) – Relation between field theory and circuit theory – Applications.

 

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

a)  Div(H) = J

b)  Div(D) = I

c)  Curl(E) = -dB/dt

d)  Curl(B) = -dH/dt

2.       Find the Maxwell law derived from Ampere law.

a)  Div(I) = H

b)  Div(H) = J

c)  Curl(H) = J

d)  Curl(B) = D

3.       The Faraday’s law states about which type of EMF?

a)  Transformer EMF

b) Back EMF

c)  Generator EMF

d) Secondary EMF

4.         In which of the following forms can Maxwell’s equation not be represented? a) Static

b)  Differential

c)  Integral

d)  Harmonic

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

a)  Conduction current

b)  Displacement current

c)  Convection current

d)  Direct current

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

a)  Curl(H) = J

b)  Curl(J) = dD/dt

c)  Curl(H) = D

d)  Curl(J) = dB/dt

7.         Find the electric flux density of a material with charge density 16 units in unit volume. a) 1/16

b)  16t

c)  16

d)  162

8.         The correct sequence to find H, when D is given is

a)  D-E-B-H

b)  D-B-E-H

c)  It cannot be computed from the data given

d)  D-H

9.         When the Maxwell equation is expressed in frequency domain, then which substitution is possible?

a)  d/dt = w/j

b)  d/dt = j/w

c)  d/dt = jw

d)  Expression in frequency domain is not possible

10.     To find D from B, sequence followed will be

a)  B-E-D

b)  B-H-D

c)  E-H-D

d)  E-B-D

11.     Maxwell second equation is based on which law?

a)  Ampere law

b)  Faraday law

c)  Lenz law

d)  Coulomb law

12.     The Maxwell second equation that is valid in any conductor is

a)  Curl(H) = Jc

b)  Curl(E) = Jc

c)  Curl(E) = Jd

d)  Curl(H) = Jd

13.     An implication of the continuity equation of conductors is given by

a)  J = σ E

b)  J = E/σ

c)  J = σ/E

d)  J = jwEσ

14.     Find the equation of displacement current density in frequency domain.

a)  Jd = jwεE

b)  Jd = jwεH

c)  Jd = wεE/j

d)  Jd = jεE/w

15.     At dc field, the displacement current density will be

a)  0

b)  1

c)  Jc

d)  ∞

16.     The charge density of a electrostatic field is given by

a)  Curl of E

b)  Divergence of E

c)  Curl of D

d)  Divergence of D

17.     From the Gauss law for electric field, we can compute which of the following parameters? a) B

b)  H

c)  E

d)  A

18.     The sequence for finding E when charge density is given is

a)  E-D-ρv

b)  E-B-ρv

c)  E-H-ρv

d)  E-V-ρv

19.     Find the sequence to find B when E is given.

a)  E-D-H-B

b)  B-E-D

c)  H-B-E-D

d)  V-E-B

20.     The sequence for finding H from E is

a)  E-B-H

b) E-V-H

c)  E-D-H

d) E-A-H

21.     Which equation will hold good for a magnetic material?

a)  Line integral of H is zero

b)  Surface integral of H is zero

c)  Line integral of B is zero

d)  Surface integral of B is zero

22.     The line integral of the electric field intensity is

a)  Mmf

b)  Emf

c)  Electric potential

d)  Magnetic potential

23.     The gradient of the magnetic vector potential can be expressed as

a)  –με dV/dt

b) +με dE/dt

c)  –με dA/dt

d) +με dB/dt

24.     Which components exist in an electromagnetic wave?

a)  Only E

b)  Only H

c)  Both E and H

d)  Neither E or H

25.     The propagation of the electromagnetic waves can be illustrated by

a)  Faraday law

b)  Ampere law

c)  Flemming rule

d)  Coulomb law

 

UNIT V ELECTROMAGNETIC WAVES

Electromagnetic wave generation and equations – Wave parameters; velocity, intrinsic impedance, propagation constant – Waves in free space, lossy and lossless dielectrics, conductors- skin depth – Poynting vector – Plane wave reflection and refraction.

1.       For a dielectric, the condition to be satisfied is

a)  σ/ωε > 1

b)  σ/ωε < 1

c)  σ = ωε

d)  ωε = 1

2.       For a perfect dielectric, which parameter will be zero?

a)  Conductivity

b) Frequency

c)  Permittivity

d) Permeability

3.         Calculate the phase constant of a wave with frequency 12 rad/s and velocity 3×10⁸ m/s(in 10^-8 order) a) 0.5

b)  72

c)  4

d)  36

4.         For a lossless dielectric, the attenuation will be

a)  1

b)  0

c)  -1

d)  Infinity

5.         Calculate the velocity of a wave with frequency 2 x10⁹ rad/s and phase constant of 4 x 10⁸ units. a) 0.5

b)  5

c)  0.2

d)  2

6.         Which of the following is the correct relation between wavelength and the phase constant of a wave?

a)  Phase constant = 2π/wavelength

b) Phase constant = 2π x wavelength

c)  Phase constant = 1/(2π x wavelength)

d) Phase constant = wavelength/2π

7.         In lossy dielectric, the phase difference between the electric field E and the magnetic field H is a) 90

b)  60

c)  45

d)  0

8.         The intrinsic impedance is the ratio of square root of

a)  Permittivity to permeability

b)  Permeability to permittivity

c)  Phase constant to wavelength

d)  Wavelength to phase constant

9.         Calculate the skin depth of a material with attenuation constant of 2 units. a) 2

b)  1

c)  0.5

d)  4

10.     Calculate the phase constant of a wave with skin depth of 2.5 units. a) 5/2

b)  5

c)  2

d)  2/5

11.     An example for lossless propagation is

a)  Dielectric waveguide propagation

b)  Conductor propagation

c)  Cavity resonator propagation

d)  It is not possible

12.     Skin depth phenomenon is found in which materials?

a)  Insulators

b)  Dielectrics

c)  Conductors

d)  Semiconductors

13.     In conductors, which condition will be true?

a)  σ/ωε > 1

b) σωε > 1

c)  σ/ωε < 1

d) σωε < 1

14.     For metals, the conductivity will be

a)  0

b)  1

c)  -1

d)  Infinity

15.     In conductors, which two parameters are same?

a)  Wavelength and phase constant

b)  Phase and attenuation constant

c)  Attenuation constant and skin depth

d)  Skin depth and wavelength

16.     Calculate the velocity of wave propagation in a conductor with frequency 5 x 10⁸ rad/s and phase constant of 3 x 10⁸ units. a) 3/5

b)  15

c)  5/3

d)  8

17.     For dielectrics, which two components will be in phase?

a)  E and wave direction

b)  H and wave direction

c)  Wave direction and E x H

d)  E and H

18.     In perfect conductors, the phase shift between the electric field and magnetic field will be a) 0

b)  30

c)  45

d)  90

19.     The expression for phase constant is given by

a)  Phase constant β = ωμε

b)  Phase constant ω = με

c)  Phase constant β = ω√(με)

d)  Phase constant β = 1/ωμε

20.     The attenuation constant in lossless dielectrics will be

a)  0

b) 1

c)  -1

d) ∞

21.     In free space, which parameter will be unity?

a)  Permittivity

b)  Absolute permittivity

c)  Relative permittivity

d)  Permeability

22.     The conductivity in free space medium is

a)  Infinity

b)  Unity

c)  Zero

d)  Negative

23.     In free space, the condition that holds good is

a)  Minimum attenuation and propagation

b)  Minimum attenuation and maximum propagation

c)  Maximum attenuation and minimum propagation

d)  Maximum attenuation and propagation

24.     The velocity of a wave travelling in the air medium without transmission lines or waveguides(wireless) is a) 6 x 10⁸

b)  3 x 10⁸

c)  1.5 x 10⁸

d)  9 x 10⁸

25.     The skin depth of a conductor with attenuation constant of 7 neper/m is a) 14

b)  49

c)  7

d)  1/7

26.     The propagation constant of the wave in a conductor with air as medium is

a)  √(ωμσ)

b) ωμσ

c)  √(ω/μσ)

d) ω/μσ

27.     Calculate the phase constant of a dielectric with frequency 6 x 10⁶ in air. a) 2

b)  0.2

c)  0.02

d)  0.002

28.     The power of a wave with electric field intensity of 3 units in air is a) 0.01

b)  0.03

c)  0.05

d)  0.07

29.     Find the power of an EM wave, given that the cross product of the E and H component is 2 + 3j. a) 2

b)  1

c)  4

d)  8

30.     The Poynting vector is the power component that is calculated by the

a)  Product of E and H

b)  Ratio of E and H

c)  Dot product of E and H

d)  Cross product of E and H

31.     Brewster angle is valid for which type of polarisation?

a)  Perpendicular

b)  Parallel

c)  S polarised

d)  P polarised

32.     The Brewster angle is expressed as

a)  Tan^-1(n)

b)  Tan^-1(n1/n2)

c)  Tan^-1(n2/n1)

d)  Tan (n)

33.     The reflection coefficient in the wave propagation when it is transmitted with the Brewster angle is a) 0

b)  1

c)  -1

d)  Infinity

34.     The transmission coefficient of a wave propagating in the Brewster angle is a) 0

b)  1

c)  -1

d)  Infinity

35.     Find the ratio of refractive index of medium 2 to that of medium 1, when the Brewster angle is 60 degree.

a)  0.707

b)  1.5

c)  0.866

d)  1.732

36.     The Brewster angle is the angle of

a)  Incidence

b) Reflection

c)  Refraction

d) Transmission

37.     The Snell’s law can be derived from which type of incidence?

a)  Incidence angle

b)  Reflected angle

c)  Refracted angle

d)  Oblique incidence

38.     The Snell’s law is given by

a)  N1 sin θi = N2 sin θt

b) N2 sin θi = N1 sin θt

c)  sin θi = sin θt

d) N1 cos θi = N2 cos θt

39.     The critical angle is defined as the angle of incidence at which the total internal reflection starts to occur. State True/False. a) True

b)  False

40.     The critical angle for two media of refractive indices of medium 1 and 2 given by 2 and 1 respectively is a) 0

b)  30

c)  45

d)  60

41.     The angle of incidence is equal to the angle of reflection for perfect reflection. State True/False. a) True

b)  False

42.     The angle at which the wave must be transmitted in air media if the angle of reflection is 45 degree is a) 45

b)  30

c)  60

d)  90

43.     When the phase angle between the Ex and Ey component is 0⁰ or 180⁰, the polarisation is

a)  Elliptical

b)  Circular

c)  Linear

d)  Perpendicular

44.     When the Ex and Ey components of a wave are not same, the polarisation will be a) Linear

b)  Elliptical

c)  Circular

d)  Parallel

45.     The Snell law is applicable for perpendicular polarisation and the Brewster law is applicable for parallel polarisation. State True/False. a) True

b)  False

46.     The characteristic impedance of a transmission line with impedance and admittance of 16 and 9 respectively is a) 25

b)  1.33

c)  7

d)  0.75

47.     The propagation constant of a transmission line with impedance and admittance of 9 and 16 respectively is a) 25

b)  144

c)  12

d)  7

48.     Find the characteristic impedance expression in terms of the inductance and capacitance parameters. a) Zo = √(LC)

b)  Zo = LC

c)  Zo = √(L/C)

d)  Zo = L/C

49.     When a transmission line has a load impedance same as that of the characteristic impedance, the line is said to be a) Parallel

b)  Perpendicular

c)  Polarized

d)  Matched

50.     The wavelength of a wave with a frequency of 6 GHz in air is a) 50

b)  5

c)  0.5

d)  0.05

51.     The velocity and phase constant relation is given by

a)  V = ω/β

b) V = ωβ

c)  V = β/ω

d) Vωβ = 1

52.     The incident wave amplitude is 24 units. Find the reflected wave amplitude if the reflection coefficient is 0.6. a) 14.4

b)  16.6

c)  13.3

d)  11.1

53.     The reflection coefficient of a wave travelling through two media having permittivities 4 and 9 respectively is a) 0

b)  0.5

c)  0.25

d)  0.2

54.     Calculate the transmission coefficient, when the incident and transmitted amplitudes are 10 and 7 respectively. a) 17

b)  3

c)  10/7

d)  0.7

55.     The transmission coefficient in a wave travelling through two media having intrinsic impedances of 5.5 and 1.33 is a) 0.389

b)  0.55

c)  0.133

d)  0.42

56.     Standing waves occurs due to

a)  Impedance match

b)  Impedance mismatch

c)  Reflection

d)  Transmission

57.     Standing wave ratio is defined as the

a)  Ratio of voltage maxima to voltage minima

b) Ratio of current maxima to current minima

c)  Product of voltage maxima and voltage minima

d) Product of current maxima and current minima

58.     Given that the reflection coefficient is 0.6. Find the SWR. a) 2

b)  4

c)  6

d)  8

59.     Find the standing wave ratio, when a load impedance of 250 ohm is connected to a 75 ohm line. a) 0.3

b)  75

c)  250

d)  3.33

60.     The range of the standing wave ratio is

a)  0 < S < 1

b)  -1 < S < 1

c)  1 < S < ∞

d)  0 < S < ∞

61.     The maximum impedance of a 50 ohm transmission line with SWR of 3 is a) 50/3

b)  3/50

c)  150

d)  450

62.     The minimum impedance of a 75 ohm transmission line with a SWR of 2.5 is a) 100

b)  50

c)  25

d)  30

63.     The standing wave ratio of short circuited and open circuited lines will be a) 0

b)  1

c)  -1

d)  ∞

64.     The intrinsic impedance in free space is

a)  60π

b)  12π

c)  6π

d)  120π

65.     A transmission line is distortionless if

a)  RL = 1/GC

b)  RL = GC

c)  LG = RC

d)  RG = LC

---

-> EE8391 Electromagnetic Theory multiple choice questions and answers

-> Anna University 3rd sem EEE Electromagnetic Theory questions and answers