GTU BE/B.Tech 2019 Winter Question Papers || Gujarat Technological University
Subject Name: Physics
Time: 10:30 AM TO 01:00 PM Total Marks: 70
GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER- I & 11 (NEW) EXAMINATION — WINTER 2019
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Subject Code: 3110011 Date: 02/01/2020Subject Name: Physics
Time: 10:30 AM TO 01:00 PM Total Marks: 70
Instructions:
- Attempt all questions.
- Make suitable assumptions wherever necessary.
- Figures to the right indicate full marks.
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| Marks | |
|---|---|
| Q.1 (a) Define: coefficient of viscosity. | 03 |
| (b) Define Reverberation time and write down the Sabine’s formula of it by explaining the parameters in it. | 04 |
| (c) What is damping motion? Derive the differential equation and general solution of damped harmonic motion. | 07 |
| Q.2 (a) Define resonance in an oscillating system. | 03 |
| (b) Draw stress- strain diagram. Explain the main points of it. | 04 |
| (c) Write down the factors affecting the acoustics of an auditorium. Give remedies. | 07 |
| OR | |
| (c) Explain Young’s Modulus, shear modulus, bulk modulus and Poisson’s ratio. | 07 |
| Q.3 (a) Write down various applications of ultrasonic waves. | 03 |
| (b) Calculate the natural frequency of 50 mm length of a pure iron rod. Given that Young’s modulus of iron = 11.5x1010N/m2 and density of pure iron = 7.25x103 kg/m3. Can you use it in a magentostriction oscillator to produce ultrasonic waves? | 04 |
| (c) Describe production of ultrasonic waves by magnetostriction method. Give its advantages and limitations. | 07 |
| OR | |
| Q.3 (a) What do you understand by NDT. Give names of few NDT methods. | 03 |
| (b) A Nikel rod having 5 cm length is vibrating at resonance. Calculate the fundamental frequency of vibration for which ultrasonic waves are generated. Given that Young’s modulus of Nikel = 2.14x1011 N/m2 , density of Nikel = 8.908 x103 kg/m3 . | 04 |
| (c) Describe acoustic diffraction method to determine the speed of sound in liquid with suitable diagram. | 07 |
| Q.4 (a) Explain the phenomenon of superconductivity. | 03 |
| (b) The critical magnetic field of Niobium is 1x 105 Tesla at 8 K and 2x105 Tesla at 0 K. Calculate the transition temperature of the element. | 04 |
| (c) Write down the applications of superconductors. | 07 |
| OR | |
| Q.4 (a) Describe BCS theory of superconductivity. | 03 |
| (b) Derive the formula for time period of a torsional pendulum. | 04 |
| (c) (i) Josephson Junction and its applications | 04 |
| (i1) What force is required to stretch a steel wire to double the length when its area of cross section is 1 cm2?. Given that Young’s modulus of wire is 7x1010 N/m2. | 03 |
| Q.5 (a) What is the wavelength of light of Ruby Laser if the separation between metastable state and lower energy state is 1.79 eV. Given that Planck’s constant = 6.64x10-34 Js. | 04 |
| (b) Describe the construction and working principle of He-Ne LASER with suitable diagrams. | 07 |
| OR | |
| (a) Classify sound on the basis of frequency with suitable examples. | 03 |
| (b) Derive the relationship between Einstein Coefficients. | 04 |
| (c) Write down the various applications of LASER. | 07 |
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