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  8. Electromagnetic Theory-I / Electrodynamics-I

Electromagnetic Theory-I / Electrodynamics-I

1: Calculate the charge density with a potential function x^2+y^2+z^2 is in air (in  order)

a. \frac{\mathbf{1}}{\mathbf{6\pi}}

b. \frac{6}{2\pi}

c. \frac{12}{6\pi}

d. \frac{10}{8\pi}

2: When a material has zero permittivity, the maximum potential that it can possess is

a. ∞

b. −∞

c. Unity

d. zero

3: A positively charged object is placed in the center of a room with a uniform magnetic field. If the magnetic field is pointing east the object will

a. Move west

b. Move east

c. Not moves

d. Move north

4: Electric polarization is observed in materials having no free charges (electrons) known as

a. Conductor

b. Insulator

c. Dielectric

d. Semi-conductor

5: A magnetic field is around

a. Iron

b. Copper

c. Aluminum

d. Moving charges

6: The total charge contain by the polarized dielectric is equal to

a. 1

b. 0

c. Constant

d. None of these

7:  A macroscopic piece of the polar dielectric is not polarized in the absence of

a. Electric field

b. Magnetic field

c. Electric potential

d. None of these

8: When a dielectric material is placed in an electric field it

a. Is charged

b. Remain un charged

c. Get polarized

d. Remain un polarized

9: The best definition of polarization is

a. Orientation in dipoles in random direction

b. Electric dipole moment per unit volume

c. Orientation of dipole moments

d. Change in polarity of every dipole

10: Dipoles are created when dielectric is placed in

a. Magnetic field

b. Electric field

c. Vacuum

d. Inert environment

11:  In free space the Poisson’s equation becomes

a. Maxwell equation

b. Ampere equation

c. Laplace equation

d. Steady State equation

12: If Laplace equation satisfies, then which of the following statements will be true?

a. Potential will be zero

b. Current will be infinite

c. Resistance will be infinite

d. Voltage will be same

13: When a dielectric material is placed in an electric field it

a. Is charged

b. Remain un-changed

c. Get polarized

d. Remains un-polarized

14: Gauss’s law is applicable for a

a. Curved surface

b. Closed surface

c. Rectangular surface

d. Equipotential surface

15: Point form of gauss’s law is

a. \nabla\cdot D=\rho v

b. \mathbf{\nabla}\cdot\mathbf{D}=\mathbf{\rho s}

c. \nabla\cdot D=\frac{\rho v}{\epsilon_\circ}

d. \nabla\cdot D=Q

16: In dielectric

a. \int{\mathbf{\rho}<em>\mathbf{v}\mathbf{dv}=\mathbf{Q}</em>\mathbf{b}}

b. \int{\rho_vdv={-Q}_b}

c. \int{\rho dv=Q_b}

d. \int{\rho_pdv=Q_b}

17: The Poisson’s and Laplace equation can be easily derived from

a. Coulomb’s law

b. Gauss’s law

c. Ampere’s law

d. Faraday’s law

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

a. Laplace equation

b. Ampere equation

c. Poisson equation

d. Maxwell equation

19: Dipoles are created when dielectric is placed in

a. Magnetic field

b. Electric field

c. Vacuum

d. Inert environment

20: A macroscopic piece of the polar dielectric is not polarized in the absence of

a. Electric field

b. Magnetic field

c. Electric potential

d. None of these

21: The best definition of polarization is

a. orientation in dipoles in random direction

b. Electric dipole moment per unit volume

c. orientation of dipole moment

d. change in polarity of every dipole

22: Calculate the polarization vector of material which has 100 dipoles per unit volume
in a volume of 2 units

a. 200

b. 50

c. 400

d. 0.02

23: Calculate energy stored per unit volume in a dielectric medium due to the polarization when

a. 1.77

b. 2.25

c. 36

d. 144

24: The unit for permeability is

a. Wb

b. At/m

c. \frac{\mathbf{Wb}}{\mathbf{At}\times\mathbf{m}}

d. \frac{At}{Wb}

25: A dielectriccan be made a conductor by

a. Compression

b. Heating

c. Freezing

d. Doping

26: Find the dielectric constant for material with dielectric susceptibility of 4

a. 3

b. 5

c. 8

d. 16

27: Magnetic field outside a solenoid is

a. Zero

b. Strong

c. Infinite

d. Negligible

28: A power line 10m high carries current 200A, the magnetic field will be

a. 2\times{10}^6T

b. 3\times{10}^6T

c. 4\times{10}^6T

d. \mathbf{5}\times{\mathbf{10}}^\mathbf{6}\mathbf{T}

29: According to SI Units, the unit of magnetic flux is

 a. Tesla

b. NmA^{-1}

c. Weber

d. CM

30: The unit of flux is the same as that of

a. Reluctance

b. Resistance

c. permeance

d. Pole strength

31: Ampere’s circuital law and which of the law is electrostatics are analogues

a. Lenz’s

b. Gauss’s

c. Biot savart’s

d. Faraday’s

32: The force between two long parallel capacitor is inversely proportional to

a. Radius of conductor

b. Current in one capacitor

c. Product of current in two conductors

d. Distance between conductors

33: H2O is a

a. Polar dielectric

b. Non-polar dielectric

c. Polar molecule

d. None of these

34: The surface integral of the normal component of the electric displacement D over any closed surface equal the charge enclosed by the surface is known as

a. Gauss’s law

b. Lenz’s law

c. Ampere’s law

d. Faraday’s laws

35: Identify a good dielectric

a. Iron

b. Ceramics

c. Plastics

d. Magnesium

36: The super conducting material will be independent of the following

a. Electric field

b. Magnetic field

c. Electric potential

d. Temperature

37: Magnetic steel is normal difficult because

a. It corrodes easily

b. It has high permeability

c. It has low permeability

d. It has high specific gravity

38: A permeable substance is one

a. Which is a good conductor

b. Which is a bad conductor

c. Which is a strong magnet

d. Through which the magnetic lines of force can pass very easily

39: The langevin Debye equation is

a. \alpha=\alpha_1+\frac{p_1^2}{3kT}

b. \mathbf{\alpha}=\mathbf{\alpha}<em>\circ+\frac{\mathbf{p}</em>\circ^\mathbf{2}}{\mathbf{3kT}}

c. \alpha=\alpha_\circ+\frac{p_\circ}{3kT}

d. None of these

40: Paramagnetic materials have relative permeability

a. Slightly less than unity

b. Equal to unity

c. Slightly more than unity

d. Equals to that ferromagnetic rails

41: Ferrites are materials

a. Paramagnetic

b. Diamagnetic

c. Ferromagnetic

d. None of these

42: Fleming’s left hand rule is used to find

a. Direction of magnetic field due to current carrying conductor

b. Direction of flux in a solenoid

c. Direction of force on a current carrying conductor in a magnetic field

d. Polarity of a magnetic pole

43: Indicate which of the following material does not retain magnetism permanently

a. Soft iron

b. Stainless steel

c. Hardened steel

d. None of the above

44: What is the value of 1 debbye in cm

a. 3.33\times{10}^{-28}\ cm

b. \mathbf{3}.\mathbf{33}\times{\mathbf{10}}^{-\mathbf{30}}\mathbf{cm}

c. 3.33\times{10}^{-32}cm

d. 3.33\times{10}^{-34}cm

45: Divergence theorem is based on

a. Stokes’s law

b. Lenz’s law

c. Ampere’s law

d. Gauss’s law

46: Conductivity is defined as ability to carry

a. Voltage

b. Resistance

c. Current

d. All

47: On dilution the specific conductance

a. Decrease

b. Increase

c. Constant

d. None

48: The dimension of current density is

a. [ML^{-2}T]

b. MLT^{-2}

c. MLT^{-2}

d. \mathbf{L}^{-\mathbf{2}}

49: Steady current only flow in

a. Continuous loop

b. Loop

c. Distorted loop

d. None

50: In a non-uniform electric field a polar molecule experience

a. Net torque

b. Net force

c. Series and parallel combination

d. None

51: Electric intensity at infinite distance from charge

a. zero

b. Infinite

c. Positive

d. None

52: Reciprocal of conductivity is called

a. Resistance

b. Inductance

c. Resistivity

d. All

53: According to Ohm’s law if voltage increase current will be

a. Decrease

b. Increase

c. Constant

d. None

54: If \nabla\times V is not equal to zero than flow is

a. Steady

b. Unsteady

c. Rotational

d. Irrotational

55: Ohm’s law is true for

a. Metallic conductor high temp

b. Metallic conductor low temp

c. Both

d. None

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