PYQ Bank

Derive an expression for magnetic susceptibility below Neel's temperature for a ferromagnetic substance.

Explain the construction and working of a p -n junction solar cell.

What is the difference between the frequency spectrum of amplitude modulated wav and frequency modulated waves? Give a circuit for the detection of frequency modulated waves.

Explain ferrimagnetism. How is it different from antiferromagnetism?

Show that in the non-degenerate approximation the Fermi level in an n-type semiconductor is slightly below the bottom of the conduction band and in p-type it is slightly above the top of the valence band, but in both cases it remains within the band gap.

Describe and explain the theory and operation of the Zener diode. Explain what is meant by (i) Avalanche breakdown (ii) Zener breakdown

Describe the characteristics of grounded emitter transistor amplifier circuit and determine expression for (i) Input resistance (ii) Output resistance (iii) Current gain (iv) Voltage gain (v) Power gain

If a signal from a high impedance source is to be amplified, which configuration is preferred and why?

Explain the formation of potential barrier in an unbiased p-n junction.

What is the role of transistor in an amplifier?

Write a short note on superconductivity.

Write a short note on zener diode.

What will happen to output voltage of an amplifier if a part of the output is returned to the input (i) in phase (ii) 180^\circ out of phase ?

Write a short note on Para and ferromagnetism.

Why do the electronic energy level in a solid form bands? Describe in terms of the band theory the difference between a conductor, an intrinsic semi-conductor and an insulator. How does the energy level change when some impurities are introduced in a semiconductor? Explain how by doping you have both n-type and p-type semiconductors starting with pure Germanium. The band gap in cases of Germanium is about 0.8\text{ eV} at Ok. Neglecting the variation of band gap with temperature, make a rough estimate of the temperature at which the resistance of a pure Germanium sample will be reduced to 1/e times its value at 300k.

How is a p-n junction prepared? Explain the charge and potential distributions in such a junction in open circuit. Explain how a p-n junction can be used to build a solar cell. Describe the mechanism of the increase of conductivity of Germanium by doping it with Arsenic.

What is superconductivity? In what kind of materials is it found to occur? Name some parameters which characterise a superconductor. Cite any two major use if we succeed in making superconductors with T_c not far atmospheric temperatures.

Write a brief scientific note on Transistor as an amplifier.

Write a brief scientific note on Logic gates and their applications.

State the difference in the electronic energy states in an isolated atom and in a solid. Hence explain difference between a conductor, an insulator and an intrinsic semiconductor. What is the role of impurities in so-called extrinsic semiconductors?