Questions for ECE

Unit I

Explain the classical free electron theory and bring out the expression for electrical conductivity of metal.
Write down the physical significance of wave function. Bring out the derivation for the particle in an infinite deep potential well and show that E = n2h2/8ml2
Describe the motion of an electron in perpendicular electric and magnetic fields.
What are the effects of electrical force and magnetic force on an electron moving with an initial velocity.
Derive an expression for density of free electrons in metal . Using that express the fermi energy of a metal at 0 k(density of states)
Define mobility of charge carriers. Deduce the relation between mobility and conductivity of metal.
Show that energy spectrum of electrons in a solid consists of allowed and forbidden bands. Based on that , distinguish between insulators, conductors, and semiconductors.(kronig penny model).
Describe the different methods of electron emission from metal surfaces.
Unit ii
1. Explain the mechanism of intrinsic conduction in semiconductors. Derive an equation for the conductivity of an intrinsic semi conductor in terms of carrier concentration and carrier mobility.
2. Sketch the variation of electrical conductivity with temperature for intrinsic and extrinsic semiconductors. What do you infer from graphs.
3. Sketch the variation of fermi level with temperature for P and N type semiconductors for high and low doping levels. Show how will you determine the band gap for a semiconductor.
4. Derive the equation of continuity for holes in p type semi conductor. Also explain , generation and recombination and mean life of charge carriers.
5. Give the theory of Hall effect for a semiconductor with neat diagram for a p type semiconductor and bring out its merits
6. Define superconductivity. Write short notes on I) Meissner effect, 2) josephson effect 3) Squids 4) magnetic levitation.
Unit III
1. What is meant by local field in a dielectric and how is it calculated for a cubic structure? Deduce claussius mosotti relation and explain its use in predicting the dielectric constant of solids.
2. Explain the different type of polarization mechanisms in dielectrics and sketch their dependence on the frequency of applied electric field.
3. Explain the langevins’ theory for a polar molecule inclined with certain angle in the presence of an applied field(orientation polarization theory)
4. Explain the frequency and temperature dependence of polarization with the help of diagrams. Explain and discuss dielectric loss.
5. Give the theory of ferro electric materials. Mention the applications of ferro electric materials.
6. Explain the importance of traps, recombination center, excitons and colour center.
7. Describe the construction and working of liquid crystal display . Mention its advantages and demerits.
Unit IV
1. Explain the domains’ theory of ferromagnetism on the basis of hysteresis curve.
2. What are hard and soft magnetic materials . What are their chief characteristics and mention their application.
3. Explain the langevin’s theory of diamagnetism and discuss its results
4. Explain the langevin’s theory of paramagnetism and bring out its results.
5. Explain weiss theory of paramagnetism and ferromagnetism
6. Write short notes on ferrites and magnetic storage materials
7. What are the general properties of para, dia, ferro magnetic materials .
8. Explain the magnetic bubble memory and its merits.
Unit V
Describe the construction and working of molecular beam epitaxy apparatus along
with its advantages and disadvantages.
Explain the Czochralski’s technique and bridgeman’s technique of bulk crystal
growth.
Explain the different steps involved in the fabrication of Ics.
Explain in detail the process of diffusion of impurities in the fabrication of Ics
Explain the metal semiconductor contact as rectifying contact and ohmic contacts
Describe the formation of monolithic diodes and explain their properties and applications.

See example problems from each unit compulsorily