Jawaharlal Nehru Technological University Hyderabad
Jawaharlal Nehru Technological University Hyderabad B.Tech IV SEMI CONDUCTORS AND MAGNETIC MATERIALS Previous Question Paper (May/June - 2019 - R15)
Part A is compulsory which carries 25 marks. Answer all questions in Part A. Part B consists of 5 Units. Answer any one full question from each unit. Each question carries 10 marks.
Part A
Define the term thermal conductivity.
Answer
Thermal conductivity is the measure of a material's ability to conduct heat. It is defined as the rate of heat flow per unit area per unit temperature gradient.
Write the different energy level and draw them.
Answer
In a solid, energy levels are grouped into bands: the Valence Band (highest occupied energy band), the Conduction Band (lowest unoccupied or partially occupied band), and the Forbidden Energy Gap (the energy range between them where no states exist).
What are the characteristics of a semiconductor?
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What do you mean by doping in semiconductor?
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Define the term Magnetic susceptibility.
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What is meant by spontaneous magnetism?
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Is the permeability of a ferromagnetic material constant? Give reasons.
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What is curie temperature?
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What is the effect of direction of grain on the magnetic properties of magnetic materials?
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What are cast and cermet permanent magnets? List them.
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Part B
Explain the first Brilloiuin zone of a two dimensional cubic lattice.
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Write short notes on thermoelectric phenomena.
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Derive the relationship between Hall coefficient and carrier density.
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Differentiate between Intrinsic and extrinsic semiconductors.
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Calculate the loss of energy caused by hysteresis in one hour in 50 kg of iron when subjected to cyclic magnetic changes. The frequency is 25 Hz, the area of the hysteresis loop represents 240 J/m3 and the density of iron is 7800 kg/m3.
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Explain the spiral structure of ferromagnetic material and explain the factors affecting the permeability in ferrites.
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Write short notes on the following magnetic materials?
a) Fe-Co alloys b) Si-Fe alloys
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What are amorphous ferromagnetic alloys and explain its structure, properties and applications?
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Explain the behaviour of Alnico’s permanent magnets under dynamic conditions.
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Write the properties and application of permanent magnetic materials.
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