M.Sc.(Semester II) (CBCS) Examination Oct/Nov-2017
Materials Science
ELECTRODYNAMICS
Day Date: Monday, 20-11-2017 Max. Marks: 70
Time: 10:30 AM to 01.00 PM
Instructions: Q. No. and Q. No are compulsory.
Attempt any three from Q. No. to Q. No.
All questions carry equal marks.
Q.1 Objective Questions:- 14
Choose correct alternative: 08
Which one of the fundamental equation was modified by Maxwell to
form the basis of electromagnetic theory?
Gauss law of electrostatic Gauss law of Magneto static
Faraday law Ampere law
2 Electromagnetic wave is incident on a dielectric-conductor interface
at a certain angle θ. The non zero electric field E will be always at
an angle.
.00 .450
.900 .600
3 Let the time dependence of an electromagnetic wave is represented
as . A wave is represented as .
.Forward travelling wave .Standing wave
.Backward travelling wave .Longitudinal wave
4 Antenna 1 has radiation resistance twice that antenna 2. It implies
that
Antenna 2 delivers double power to space than antenna 1
Antenna 2 delivers half power to space than antenna 1
Antenna 2 delivers quarter power to space than antenna 1
Antenna 2 delivers equal power to space than antenna 1
5 In a capacitor, the electric charge is stored in
Metal plates
Neither in metal plate or dielectric
Dielectric as well as metal plates
Dielectric
6 For a ground in a rural area 14 and conductivity σ 10-2. At a
microwave frequency of 30 GHZ, the ground will act like a
Dielectric Conductor
Quasi-Conductor None of the above
Two non-magnetic media have refractive indices n1 and n2. The ratio
of reflected and incident electric field Er/Ei is
n1/n2 n2/n1
(n1/n2 (n1/n2 None of the above
Page 2 of 2
SLR-MO-523
Time average of magnitude of pointing vector is called as
Irradiance Electric field amplitude
Power Electromagnetic Energy
State True or False: 06
Lorentz condition is invariant in those gauge functions which are the
solutions of homogeneous wave equations.
When an EM wave is incident on a dielectric, it is partially transmitted
and partially reflected.
The incident, reflected, refracted waves and also the normal to the
interface do not lie in the same plane.
The electric potential due to linear quadrapole varies inversely with
r3.
The normal components of electric displacement is not continuous
across the interface and changes by an amount equal to the surface
density of charge at the interface.
Radiation resistance of a λ/2 dipole is infinite.
Q.2 Write short notes on: 14
State and explain the Faraday's laws electromagnetic induction. 04
Show that for a conductor subject to electric field
Displacement current density is negligible compared to conduction density
at frequencies less than 1015Hz.
04
Derive equation of continuity using Maxwell's equations. 04
Define displacement current. 02
Q.3 Prove Ponyting's theorem relating to the flow of energy at a point in
space in an electromagnetic field.
08
Prove the electromagnetic waves are transverse waves. 06
Q.4 Obtain Lorentz condition which exhibits interrelationship of
electromagnetic potentials.
08
Define Alembertian operator. Write Maxwell's field equation by
applying Lorentz condition and Alembertian operator.
06
Q.5 What is the physical meaning of radiation resistance? Obtain its value for
a dipole antenna. Justify the selection of λ/2 antenna on this basis.
08
Set up an equivalence between electric dipole and current elements 06
Q.6. What is the physical meaning of radiation resistance? Obtain its value
for a dipole antenna. Justify the selection of λ/2 antenna on this basis.
08
Write a note on Gauge transformations. 06
Q.7 Establish Maxwell's equations for propagation of electromagnetic wave in
a conducting media and show that the wave penetrated the conducting
medium to a depth and inside the conductor the magnetic vector B
lags behind the electric field vector E.
08
Show that the electrostatic energy density is equal to magnetostatic
energy density.