Download GTU BE/B.Tech 2019 Summer 1st And 2nd Sem (New And SPFU) 3110018 Physics Question Paper

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GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER-I & II (NEW) EXAMINATION — SUMMER-2019

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Subject Code: 3110018 Date: 03/06/2019
Subject Name: Physics
Time: 10:30 AM TO 01:00 PM Total Marks: 70

Instructions:

1. Attempt all questions.

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2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.

Q.1

(a) Give formation and applications of SQUID. [03]
(b) Explain intrinsic and extrinsic semiconductors with necessary diagram. [04]

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(c) What is PN junction diode? What is external bias? Describe its forward and reverse bias conditions with appropriate diagram. [07]

Q.2

(a) What is photo conductivity, photoluminescence, phototransistor? [03]
(b) Calculate the energy gap of Si, given that radiation of wavelength 11,000 Å is incident on it. Also find allowed wavelength for Ge with energy gap 0.90 eV. [04]
(c) Write a note on energy band diagram and formation of energy bands. [07]

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OR

(c) Define Hall effect and Hall coefficient. Derive equation to find Hall voltage. What does it signify? [07]

Q.3

(a) Differentiate between soft and hard superconductors [03]
(b) What is London penetration depth? Derive its equations. [04]

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(c) Derive equations for n-type semiconductor to determine dependence of fermi level on temperature and doping concentration. [07]

OR

(a) The critical current density equal to 1.71 x 10³ A/m² is required to change a superconducting wire of radius 0.5 mm at 4.2 K. If the critical temperature of the material is 7.18 K, calculate the maximum value of the critical magnetic field. [03]
(b) Explain BCS theory for superconductivity. [04]
(c) Write a note on metal semiconductor junctions. [07]

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Q.4

(a) Write a note on exciton. [03]
(b) Give details of applications of solar cell (at least 4) [04]
(c) What is radiative and non-radiative transition. Explain in brief the optical joint density of states. [07]

OR

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(a) What are direct and indirect band gap? [03]
(b) What is deep level transient spectroscopy (DLTS)? Give its experimental procedure. [04]
(c) Discuss the technique to obtain band gap by UV-Vis spectroscopy using absorption or transmission. [07]

Q.5

(a) What are capacitance voltage measurements? [03]

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(b) Consider n-type silicon semiconductor with a length of 100 µm, cross sectional area 10^-7 cm², minority charge carrier life time 10^-6 s, µ_e is 0.13 m²/Vs and µ_h is 0.05 m² / Vs. Find (a) Electron transit time [04]

(c) Discuss Van Der Pauw method. [07]

OR

Q.5 (a) What is the cause and remedy for optical loss in photovoltaic cell? [03]
(b) State principle and discuss working of semiconductor laser. [04]

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(c) What is photovoltaic effect? Explain construction and working of a solar cell with suitable diagram [07]

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