Download SGBAU BSc 2019 Summer 3rd Sem Physics Question Paper

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B.Sc. (Part-II) Semester—III Examination

PHYSICS

Time : Three Hours] [Maximum Marks : 80

Note :— (1) All questions are compulsory.
(2) Draw suitable and neat diagram wherever necessary.

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1. (A) Fill in the blanks :— 2
   1. The input impedance of an ideal OPAMP is ___________.
   2. The maximum concentration of ozone gas lies in __________ layer of earth’s atmosphere.
   3. For operation of transistor in active region the collector-base junction must be __________ biased.
   4. The value of transistor current gain in CB mode (α) is always __________ than 1.

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2. (B) Choose correct alternative :— 2
   1. Electric flux is a __________ quantity.
      1. scalar
      2. vector
      3. constant
      4. zero

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   2. When a trivalent impurity is added to pure semiconductor, it becomes ?
      1. An insulator
      2. An Intrinsic semiconductor
      3. p-type semiconductor
      4. n-type semiconductor

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   3. The Hall coefficient R_H is negative for
      1. Intrinsic semiconductor
      2. p-type semiconductor
      3. n-type semiconductor
      4. None of the above

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   4. Common mode rejection ratio is :
      1. A_v (Diff.) / A_v (Com.)
      2. A_v (Com.) / A_v (Diff.)
      3. A_v(Com.) + A_v(Diff.)
      4. A_v(Com.) x A_v(Diff.)

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3. (C) Answer in ONE sentence :— 4
   1. Define Extrinsic semiconductor.
   2. What is fermi level ?
   3. What is Epicenter of earthquake ?
   4. Write down the relation between three parameters of the FET.

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2. (A) Define divergence of a vector and give its physical significance. 4
   (B) State and prove Stoke’s theorem. 6
   (C) Explain line integral with example. 2
   OR

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3. (P) State and prove Ampere’s Law. 6
   (Q) Derive an expression for work done on charge in an electrostatic field 6
   (R) Explain Lorentz force equation. 2

4. (A) State Faraday's law of electromagnetic induction and derive an expression
   ∇ × E = -∂B/∂t. 6
   

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   (B) Derive the relation ∇.D=ρ. 4
   (C) State Maxwell's equations for free space. 2
   OR

5. (P) What is Poynting vector ? Explain its physical significance. 4
   (Q) Obtain the equation : ∇ × H = J + ∂D/∂t. 6
   

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   (R) What is characteristic impedance of electromagnetic wave ? 2

6. (A) What is Hall effect ? Derive an expression for Hall coefficient 7
   (B) Explain construction and working of LED. 5
   OR

7. (P) Describe n-type and p-type semiconductor. 6
   

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   (Q) Explain forward and reverse biasing of p-n junction diode 4
   (R) Explain potential barrier in pn-junction diode 2

8. (A) Explain the construction and working of n-channel JFET. 5
   (B) Draw a block diagram of operational amplifier and explain working of each block. 5
   (C) A given transistor has current gain β = 50, calculate the value of α ? 2
   

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   OR

9. (P) Explain working of NPN transistor. 5
   (Q) Explain how op-amp can be used as an inverting amplifier. 5
   (R) Draw circuit diagram to plot the characteristics of JFET. 2

10. (A) State postulates of special theory of relativity. 2
    

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    (B) Derive Lorentz transformation equations. 6
    (C) Explain length contraction and derive the expression for the same. 4
    OR

11. (P) Obtain an expression for relativistic addition of velocities using lorentz transformation. 6
    (Q) Derive Einstein’s mass-energy relation E = mc² 6

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12. (A) What is earthquake ? Explain different types of earthquakes. 6
    (B) Explain internal structure of earth. 6
    OR

13. (P) Explain the scattering, absorption and reflection of solar radiation by atmosphere. 6
    (Q) What are the seismic waves ? Explain different types of seismic waves. 3
    

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    (R) Explain the vertical division of atmosphere on the basis of temperature. 3

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