PH3254 Physics for Electronics Engineering Important Questions

PH3254 Physics for Electronics Engineering

Important Questions

Unit 1

1. Write a short note on
   (i) crystal system
   (ii) packing factor
   (iii) wafer surface orientation and
   (iv) diamond cubic structure
2. Describe the steps to determine the miller indices and also mention its importance.
3. Discuss briefly about simple and closed packed hexagonal structure and calculate the c/a ratio and packing factor of the HCP with neat diagram.
4. The height of the HCP unit cell is 0.494 nm and the nearest neighbor distance is 0.27 nm. The atomic weight of zinc is 65.37. Calculate the volume of the unit cell.
5. Discuss briefly the crystal directions and Miller indices with its procedures to represent (100), (110), (111) and (200) planes of a cubic crystals.
6. Show the expression for separation between two lattice planes in a crystal with schematic.

Unit 2

1. Derive an expression for the density of energy states in a metal.
2. What is a GMR device? Describe the construction and working methods of GMR.
3. Derive the expression for thermal conductivity and electrical conductivity and obtain the relation between them using classical free electron theory.
4. Briefly discuss the origin of ferromagnetism and exchange interaction in ferromagnetic materials.
5. The saturation magnetic induction of nickel is 0.65 wb/m². If density of nickel is 8906 kg/m³ and its atomic weight is 58.7, calculate the magnetic moment of the nickel atom in Bohr magneton.

Unit 3

1. Briefly discuss the origin of energy bands in semiconductors with schematic and differentiate between direct and indirect band gap semiconductors with necessary diagrams.
2. In a p-type germanium, n=2.1×10m³, density of boron 4.5×1023 atoms m³. The electron and hole mobilities are 0.4 and 0.2 m²/volt-s, respectively. What is it’s conductivity before and after the addition of boron atoms?
3. ) Discuss Hall effect and derive the expression for Hall coefficient and draw experimental setup to determine Hall mobility of semiconductor.
4. A semiconducting crystal 12 mm long, 5 mm wide and 1 mm thick has a magnetic flux density of 0.5 wb/m² applied from front to back, perpendicular to largest faces. When a current of 20 mA flows length wise through the specimen, the voltage measured across its width is found to be 37 V. What is the Hall coefficient of this semiconductor?
5. Derive an expression for density of electrons in conduction band of an n-type semiconductor.
6. State and explain Hall effect. With necessary theory and diagram, derive the Hall coefficient of a semiconductor.

Unit 4

1. Discuss the optical process in quantum well with necessary diagram.
2. Explain the principle and working of LED with a neat diagram and mention its advantages and disadvantages,
3. Explain briefly about optical absorption in quantum well along with energy band diagram in the presence and absence of a transverse electric field in semiconductor.
4.  Calculate the energy of the electron and heavy hole produced by absorbing a 1.5 eV photon in InP. (Given & of InP = 1.35 eV, m=0.082m, mhh = 0.085m, and mo = 0.075m.
5. Describe briefly the principle of operation and IV characteristic of Photovoltaic device with neat diagram.
6. The light intensity of 700 W/m² falls on a solar cell having the surface area of 0.03m x 0.03m, the resultant current and voltage generated are 157 mA and 475 mV, respectively. Calculate the efficiency of the photovoltaic device.

Unit 5

1. What happens to the energy, momentum and position of an electron in an isolated thin semiconductor when it is quantum confined along one dimension ie., quantum wells?
2. Discuss briefly the bandgap of nanomaterials of conductors, semiconductor and insulators.
3. What are carbon nanotubes (CNTs)? Explain briefly the properties and applications of CNTs with neat diagram.
4. Discuss briefly about spintronic devices and its applications.
5. Write a detailed note on quantum confinement and quantum structure.
6. Design a transistor in which the current flows from source to drain due to movement of only one electron at a time. Explain the conditions necessary for this single electron phenomenon and the working of the Single electron transistor.