Physics 2075

Attempt any two questions:

1. Explain the process of semiconductor purification by describing the terms Zone refining, single crystal growth, and scheme of IC production. Give an account of electronic component fabrication on a chip.

2. Set up differential equation for an oscillation of a spring using Hooke's and Newton's second law. Find the general solution of this equation and hence the expressions for the period, velocity and oscillation of the acceleration.

4. Discuss magnetic dipole moment. What is its effect on atom and on molecules? Explain.

Attempt any eight questions:

5. Explain Blotch theorem? Discuss its use in Kronig-Penny model and hence in band theory.

6. Explain the construction and working of bipolar junction transistor (BJT).

7. A large wheel of radius 0.4m and moment of inertia 1.2 kg-m², pivoted at the center, is free to rotate without friction. A rope is wound around it and a 2-kg weight is attached to the rope. When the weight has descended 1.5m from its starting position (a) what is its downward velocity? (b)what is the rotational velocity of the wheel? 

8. An electron is placed midway between two fixed charges, q₁ = 2.5 x 10^-10 C  and q₂ = 5 x 10^-10 C. If the charges are 1 m apart, what is the velocity of the electron when it reaches a point 10cm from a q₂?

9. A small particle of mass 10^-6 gm moves along the x axis;  its speed is uncertain 10^-6 m/sec. (a) What is the uncertainity in the x coordinate of the particle? Repeat the calculation for an electron assuming that the uncertainity in its velocity is also 10^-6 m/sec. Use the known value for  electrons and Plank's constant. 

10. What is the probability of finding a particle in a well of width a at a position a/4 from the wall if n = 1, if n = 2, if n = 3. Use the normalized wavefunction 

11. Assuming that atoms in a crystal structure and arranged as closed-packed spheres, what is the ratio of the volume of the atoms to the volume available for the simple cubic structure? Assume a one-atom basis. 

12. The output of a digital circuit (y) is given by this expression: ,where A,B and C represent inputs. Draw a circuit of above equation using OR, AND and NOT gate and hence find its truth table.