Master of Science I (Physics Material Science)
Examination: Oct/Nov 2016 Semester II (Old CGPA)
SLR No. Day
Date Time Subject Name Paper
No. Seat No.
SLR SH
547
Tuesday
22/11/2016
10.30 AM
To
01.00 PM
Electrodynamics
C
VII
Instructions: Q. no. 1 and Q. no 2 are compulsory
Attempt any three questions from Q. No.3 to Q. No. 7
All questions carry equal marks.
Use of non programmable calculator is allowed
Total Marks: 70
Q.1 Choose the correct alternative 08
Maxwell inserted the expression for displacement current JD in Ampere's law
to satisfy
Ampere's law for time varying case Faraday's law
Gauss law Equation of continuity
The effective length of an antenna depends on
The wavelength of radiation Angle of radiation
The current distribution Area of cross section
Which of the following circuit element will oppose the change in circuit
current?
Capacitor Resistor
Inductor All of the above
If a dipole is displaced through a small distance and the original dipole is then
replaced by one of the same magnitude but of opposite sign
a monopole is formed multiple are formed
octupole is formed quadrupole is formed
The depth of penetration is defined as that depth in which the wave attenuates
to
50% of its strength before
penetration
20% of its strength before
penetration
70% of its strength before
penetration
1/e times of its strength before
penetration
The formulae relating the amplitude of the reflected and transmitted waves
with that of incident wave are known as
Fresnel formulae Fraunhofer formulae
Kirchhoff formulae Maxwell formulae
In a dielectric conductor boundary (interface), the tangential components of
electric field is
Et 2Et
∞ Zero
The directive gain cannot be started as
Independent of angles The directivity of an antenna when
directive gain is maximum
The function of angles The ratio of the radiation intensity
in that direction to the average
radiated power.
Page 1 of 2
State True of False 06
One of the Maxwell's equations (in free space) in Differential form is as
follows 0 If a magnetic monopole exists, then this equation will be
modified.
In equipotential surface, potential is different everywhere.
Transverse electric wave travelling in direction satisfies Ez Hz 0
Radiation resistance of a λ dipole is infinite.
The electric potential due to linear quadrapole varies inversely with r3.
When an EM wave is incident on a dielectric, it is partially transmitted and
partially reflected
Q.2 Write short answers. 14
Show how can you degenerate multipole poitentials from that of a single
charge.
Show that for a conductor subjected to electric field E Eo cos ωt
displacement current density is negligible compared to conduction density at
frequencies less than 1015 Hz.
Derive equation of continuity using Maxwell's equations.
04
05
05
Q.3 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 δ and inside the conductor, the magnetic vector B lags
behind the electric field vector E.
Obtain Poynting theorem for the conservation of energy for the
electromagnetic field.
08
06
Q.4 Obtain Lorentz condition. Apply it on the Maxwell's field equation expressed
in terms of electromagnetic potentials and A.
Define Alembertian operator. Write Maxwell's field equation by applying
Lorentz condition and Alembertian operator.
08
06
Q.5 Obtain the expression for the electric and magnetic fields of an oscillating
electric dipole. Hence calculate the ponyting vector and total radiated power.
Set up equivalence between electric dipole and current element.
10
04
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.
Write a note on coulomb guage.
10
04
Q.7 A plane electromagnetic wave is incident on a plane boundary between the
two non-conducting media. Specify the boundary conditions and hence derive
Fresnel's formulae for the reflected and transmitted intensities.
State and explain the Faraday's laws of electromagnetic induction.
10
04
Page 2 of 2