Electrostatics - II - ELECTROMAGNETICS MCQs

Multiple Choice Questions 8 Pages

Savitribai Phule Pune University

electrical engineering

Contributed by

Yadu Deshmukh

DEPARTMENT OF ELECTRONICS AND TELECOMMUNICATION
---------------------------------------------------------------------------------------
MCQ UNIT 2-Electrostatics – II
1) The Coulomb law is an implication of which law?
a) Ampere law
b) Gauss law
c) Biot Savart law
d) Lenz law
2) A charge of 2 X 10
-7
C is acted upon by a force of 0.1N. Determine the distance to the
other charge of 4.5 X 10
-7
C, both the charges are in vacuum.
a) 0.03
b) 0.05
c) 0.07
d) 0.09
3) For a charge Q1, the effect of charge Q2 on Q1 will be,
a) F1 = F2
b) F1 = -F2
c) F1 = F2 = 0
d) F1 and F2 are not equal
4) The lines of force are said to be
a) Real
b) Imaginary
c) Drawn to trace the direction
d) Not significant
5) Electric flux density in electric field is referred to as
a) Number of flux lines
b) Ratio of flux lines crossing a surface and the surface area
c) Direction of flux at a point
d) Flux lines per unit area
6) The electric flux density is the
a) Product of permittivity and electric field intensity
b) Product of number of flux lines and permittivity
Page 1
c) Product of permeability and electric field intensity
d) Product of number of flux lines and permeability
7) Which of the following correctly states Gauss law?
a) Electric flux is equal to charge
b) Electric flux per unit volume is equal to charge
c) Electric field is equal to charge density
d) Electric flux per unit volume is equal to volume charge density
8) The Gaussian surface is
a) Real boundary
b) Imaginary surface
c) Tangential
d) Normal
9) Find the flux density of a sheet of charge density 25 units in air.
a) 25 b) 12.5 c) 6.25 d) 3.125
10) A uniform surface charge of σ = 2 μC/m
2
, is situated at z = 2 plane. What is the value of
flux density at P(1,1,1)m?
a) 10
-6

b) -10
-6

c) 10
6

d) -10
6
11) Find the flux density of line charge of radius (cylinder is the Gaussian surface) 2m and
charge density is 3.14 units?
a) 1
b) 0.75
c) 0.5
d) 0.25
12) 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
13) Find the electric field intensity of transformer oil (εr = 2 approx) with density 1/4π (in
10
9
units)
a) 2.5
b) 3.5
c) 4.5
d) 5.5
Page 2
14) Gauss law can be used to compute which of the following?
a) Permittivity
b) Permeability
c) Radius of Gaussian surface
d) Electric potential
15) Three charged cylindrical sheets are present in three spaces with σ = 5 at R = 2m, σ = -
2 at R = 4m and σ = -3 at R = 5m. Find the flux density at R = 1m.
a) 0
b) 1
c) 2
d) 3
16) Three charged cylindrical sheets are present in three spaces with σ = 5 at R = 2m, σ = -
2 at R = 4m and σ = -3 at R = 5m. Find the flux density at R = 3m.
a) 3
b) 10/3
c) 11/3
d) 4
17) Gauss law can be evaluated in which coordinate system?
a) Cartesian
b) Cylinder
c) Spherical
d) Depends on the Gaussian surface
18) With Gauss law as reference which of the following law can be derived?
a) Ampere law
b) Faraday’s law
c) Coulomb’s law
d) Ohm’s law
19) 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 line
20) 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
Page 3
21) Equipotential surface is a
a) Real surface
b) Complex surface
c) Imaginary surface
d) Not existing surface
22) If the electric potential is given, which of the following cannot be calculated?
a) Electrostatic energy
b) Electric field intensity
c) Electric flux density
d) Permittivity
23) Superconductors exhibit which of the following properties?
a) Ferromagnetism
b) Polarisation
c) Diamagnetism
d) Ferrimagnetism
24) The permittivity is also called
a) Electrostatic energy
b) Dielectric constant
c) Dipole moment
d) Susceptibility
25) Find the potential at a point (4, 3, -6) for the function V = 2x
2
y + 5z.
a) 96
b) 66
c) 30
d) -66
26) If V = 2x
2
y + 20z – 4/(x
2
+ y
2
), find the density at A(6, -2.5, 3) in nC/m
2
.
a) 0.531i – 0.6373j – 0.177k
b) 0.6373i – 0.177j -0.531k
c) 0.177i – 0.6373j – 0.531k
d) 0.531i – 0.177j – 0.6373k
27) The continuity equation is a combination of which of the two laws?
a) Ohm’s law and Gauss law
b) Ampere law and Gauss law
c) Ohm’s law and Ampere law
d) Maxwell law and Ampere law
28) Calculate the charge density for the current density given 20sin x i + ycos z j at the
origin.
a) 20t
Page 4
b) 21t
c) 19t
d) -20t
29) 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
30) 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
31) The capacitance of a material refers to
a) Ability of the material to store magnetic field
b) Ability of the material to store electromagnetic field
c) Ability of the material to store electric field
d) Potential between two charged plates
32) A cable of core radius 1.25cm and impregnated paper insulation of thickness 2.13cm
and relative permittivity 3.5. Compute the capacitance of the cable/km(in nF)
a) 195.7
b) 179.5
c) 157.9
d) 197.5
33) The best definition of polarisation is
a) Orientation of dipoles in random direction
b) Electric dipole moment per unit volume
c) Orientation of dipole moments
d) Change in polarity of every dipole
34) Polarizability is defined as the
a) Product of dipole moment and electric field
b) Ratio of dipole moment to electric field
c) Ratio of electric field to dipole moment
d) Product of dielectric constant and dipole moment
35) Calculate the energy stored per unit volume in a dielectric medium due to polarisation
when P = 9 units and E = 8 units.
Page 5
a) 1.77
b) 2.25
c) 36
d) 144
36) The total polarisation of a material is the
a) Product of all types of polarisation
b) Sum of all types of polarisation
c) Orientation directions of the dipoles
d) Total dipole moments in the material
37) 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
38) Find the electric field if the surface density at the boundary of air is 10
-9
.
a) 12π
b) 24π
c) 36π
d) 48π
39) Which component of the electric field intensity is always continuous at the boundary?
a) Tangential
b) Normal
c) Horizontal
d) Vertical
40) The normal component of which quantity is always discontinuous at the boundary?
a) E
b) D
c) H
d) B
41) The electric field intensity of a surface with permittivity 3.5 is given by 18 units. What the
field intensity of the surface in air?
a) 5.14
b) 0.194
c) 63
d) 29
42) In free space, the Poisson equation becomes
a) Maxwell equation
b) Ampere equation
Page 6
c) Laplace equation
d) Steady state equation
43) 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
44) Poisson equation can be derived from which of the following equations?
a) Point form of Gauss law
b) Integral form of Gauss law
c) Point form of Ampere law
d) Integral form of Ampere law
45) Find the charge density from the function of flux density given by 12x – 7z.
a) 19
b) -5
c) 5
d) -19
46) In free space, which of the following will be zero?
a) Permittivity
b) Permeability
c) Conductivity
d) Resistivity
47) 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
48) Calculate the energy in an electric field with permittivity of 56 and field intensity of
36π(in μJ)
a) 3.16
b) 5.16
c) 7.16
d) 9.16
49) The Stoke’s theorem uses which of the following operation?
a) Divergence
b) Gradient
c) Curl
d) Laplacian
Page 7
50) Which of the following theorem convert line integral to surface integral?
a) Gauss divergence and Stoke’s theorem
b) Stoke’s theorem only
c) Green’ s theorem only
d) Stoke’s and Green’s theorem

Page 8