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Model Question Paper-2 with effect from 2018-19
(CBCS Scheme)
18PHY12/22
USN
First/Second Semester B.E.Degree Examination
Engineering Physics
(Common to all Branches)
Time 3 hrs Max. Marks: 100
Note: 1. Answer FIVE full questions, choosing ONE full question from each module.
2. Physical constants: Speed of light c 3 108m/s; h 6.625 10 -34JS; k 1.38 10
NA 6.02 10 63/Kmole; me 9.1 10-31kg; e 1.6 10-19C.
Module 1
1 a. Starting form Hookes' law derive the differential equation for SHM. Explain the Characteristics of SHM. marks)
b. With a neat diagram explain the construction and working of Reddy tube. Mention any four applications of Shock waves (10 marks)
c. A mass of 4.3gm is attached to a spring of force constant 17N/m. This mass spring system is executing SHM. Find the frequency of the external force which excites resonance in the system. Ignore the mass of the spring. marks)
OR
2 a. State and explain laws of conservation of mass, energy and momentum. marks)
b. What are damped oscillations? Derive the expression for decaying amplitude and hence discuss the case of critical damping (10 marks)
c. A 20 gm oscillator with a natural frequency 10rad/s is vibrating in damping medium. The damping force is proportional to the velocity of the vibrator. If the damping coefficient is 0.17 how does the oscillation decays? marks)
Module-2
3. a. Explain tensile stress and compressive stress. What are the engineering importances of elastic materials? marks)
b. Define lateral strain, linear strain and Poisson's ratio. Obtain the expression for Poisson's ratio (10 marks)
c. What are torsional oscillations? Give the expression for time period of torsional oscillations. Mention the applications of torsional oscillations marks)
d. A wire of length 2m and radius 2mm is fixed to the center of a wheel. A torque of magnitude 0.0395Nm is applied to twist the wire. Find the rigidity modulus of the wire if the angular twist is 0.038rad marks)
OR
4. a. Define bending moment. Derive the expression for bending moment in terms moment of inertia. marks)
b. Derive the relation between bulk modulus Young's modulus and Poisson's ratio. What are the limiting values of Poisson's ratio? marks)
c. A brass bar of length 1m, area of cross section 0.01m2 is clamped horizontally at one end. A weight of 1kg is applied at the other end. What is the depression produced modulus is 9.78 x 10 10 Nm2 marks)
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Module-3
5. a. Describe the concept of divergence. What is its physical significance? Derive Gauss divergence theorem marks)
b. With neat diagrams explain different types of optical fiber. Define V number (7marks)
c. A coil of mean radius 8cm and having 100 turns carries current of 10A. Calculate the magnetic field produced at the center of the coil and at a point on the axis at a distance 4cm from the center (4marks)
OR
6. a. With the help of Block diagram, explain point to point communication using optical fiber. Mention the merits and de merits of optical fiber communications (10marks)
b. What is displacement current?. Derive the expression for displacement current (6marks)
c. An optical fiber has core refractive index 1.5 and clad refractive index less than that of core. Calculate NA, angle of acceptance, and internal critical angle (4marks)
Module 4
7. a. Staring from Schrodinger's time independent wave equation, derive the expression for energy eigen value and eigen function for an electron present in 1-d potential well of infinite depth. (10 marks)
b. What is a laser range finder? Give the qualitative explanation of construction and working of laser range finder marks)
c. An electron is trapped in a 1-D potential well of infinite height and width of 0.1nm. Calculate the energy required to excite it from its ground state to fifth excited state marks)
OR
8. a. Explain the terms spontaneous emission, stimulated emission population inversion active medium and resonance cavity (10 marks)
b. What are the properties of a wave function? Give the qualitative explanation of Max Born's interpretation of wave function marks)
c. A laser operating at 632.8nm emits 3.182 x 1016 photons per second. Calculate the output power of the laser if the input power is 100 watt. Also find the percentage power converted into coherent light energy marks)
Module 5
9. a. Give the assumptions of quantum free electron theory. Discuss two success of quantum
free electron theory marks)
b. What are dielectrics? Give the relation between dielectric constant and polarization. Discuss solid, liquid and gaseous dielectrics with one example for each. marks)
c. Define Fermi temperature. Calculate Fermi temperature for a metal whose Fermi energy is 7eV marks)
OR
10. a. Describe Fermi level in intrinsic semiconductor and hence obtain the expression for
Fermi energy in terms of energy gap of intrinsic semiconductor (8marks)
b. Give a brief account for Fermi-Dirac distribution theory. Obtain the expression for Fermi
energy at 0 K (8marks)
c. The conductivity and Hall coefficient of an n-type semiconductor are and 1.25 x 10 -3m3/C respectively. Calculate the charge carrier concentration and electron mobility
marks)