Visvesvaraya Technological University (VTU) 2007 B.E Electrical and Electronics Engineering nModel__.rtf - Question Paper

Visveswaraiah Technological University
I/II semester BE exam
Engineering Physics

MODEL ques. PAPER

Duration: three hours Max marks:100

Note: 1.Answer 5 full Questions, choosing atleast 2 ques. from every part.

2. every ques. carries 20 marks.

3. ans must be specific and precise.

4. Draw neat sketches wherever necessary.

Physical constants:
Electron mass (m) = 9.11 x 10-31 kg
Electron charge (e) = 1.6 x 10-19 C
Plank’s constant (h) = 6.63 x 10-34 J/s
Velocity of light (c) = three x 108 m/s
Permittivity of vacuum (e0) = 8.854 x10-12 F/m
Avogadro number (NA) = 6.025 x 1026 /k mol
Boltzmann constant (K) =1.38 x 10-23 J/k

PART - I

1. a) discuss briefly the distribution of energy in the block body radiation.
b) define Davission and Germer’s experiment to establish the wave nature of electrons.
c) A particle of mass 0.5Mev/c2 has kinetic energy 100 eV. obtain its debroglie wave length.
[Marks(5+10+5)]

2. a) discuss Heisenberg’s uncertainty principle. provide its physical significance.
b) Assuming the time independent Schrödinger wave equation, explain the solution for a
particle in 1 dimensional potential well of infinite height. Hence find the normalized wave
function.
c) An electron is bound in 1 dimensional potential well of infinite height of width 0.12nm.
obtain the energy values in the ground state and also the 1st 2 excited states.
[Marks (10+5+5)]

3. a) discuss the terms Drift velocity, mobility and relaxation time.
b) Based on free electron theory, derive an expression for electrical conductivity in metals and
explain the failures of classical free electron theory.
c) obtain the temperature at which there is 1% probability that a state with and energy 0.5eV
above Fermi energy will be occupied.
[Marks (5+10+5)]

4 a) define in brief the Ionic polarization and electronic polarization.
b) elaborate dialectics? Derive an expression for internal field in case of solids and liquids.
c) The dielectric constant of He gas at NTP is 1.0000684. compute the electric polarizability of
He atoms if the gas contains 2.7x1025 atoms / m3.
[Marks (5+10+5)]

PART - II

5. a) discuss the process of stimulated emission and population inversion.
b) discuss the construction and working of He-Ne laser. discuss briefly use of laser in
measurement of pollutants in the atmosphere.
c) A pulsed laser emits photons of wave length 780nm with 20mW avg. power/pulse.
compute the number of photons contained in every pulse if the pulse duration is 10 ns.
[Marks (5+10+5)]

6. a) discuss kind I and kind II Superconductors
b) Derive an expression for numerical aperture in terms of refractive indices of core and
cladding. With the help of a block diagram define point to point communication system.
c) A fiber with an input power of 9.0µW has a loss of1.5dB/km. If the fiber is 3000 m long
what is the out put power?
[Marks (5+10+5)]

7. a) discuss unit cell and primitive cell.
b) elaborate Miller indices? Derive an expression for inter planar spacing of a crystal in terms of
Miller indices.
c) Draw the subsequent planes in a cubic unit cell (011), (102), (132) and (112).
[Marks (5+10+5)]

8. a) discuss carbon nanotubes and its applications by giving their physical properties.
b) elaborate ultrasonic waves? define the method of testing the materials using ultrasonic
waves.
[Marks (10+10)]

Earning:   Approval pending.