BE Automobile Engineering सत्र १ (इंजीनियरिंग) - University of Mumbai Question Bank Solutions

What do you mean by group and phase velocity? Show that the de-Broglie group velocity associated with the wave packet is equal to the velocity of the particle.

The mobility of holes is 0.025m² /V-sec. what would be the resistivity of n- type Si if the Hall coefficient of the sample is 2.25× 10^-5m³/C. 

Define drift current, diffusion current and P-N junction. The electrical conductivity of a pure silicon at room temperature is 4×10^-4 mho/m . if the mobility of electron is 0.14m² /V-S and that of hole is 0.04m² /V-S. calculate the intrinsic
carrier density.

What is the wavelength of a beam of neutron having:
⦁ An energy of 0.025 eV?
⦁ An electron and photon each have wavelength of 2A°. what are their momentum and energy ? m_n = 1.676×10^-27 kg, h = 6.625×10^-34 J-sec. 

Calculate the frequency and wavelength of photon whose energy is 75eV.

Mobility of electron and hole in a sample of Ge at room temperature are 0.36 m² /V-sec and 0.17m² /V-sec respectively. If electron and holes densities are equal and it is 2.5 ×10¹³ /cm³ , calculate its conductivity.

State the piezoelectric effect. With neat circuit diagram explain the principle and working of piezoelectric oscillator .

Calculate electron & hole concentration in intrinsic Si at room temperature if
its electrical conductivity is 4x10-4 mho/m.Given that mobility of electron=
0.14m2/V-sec and  mobility of holes=0.04m2/V-sec.

Show that for intrinsic semiconductors of the Fermi level lies midway between the conduction band and the valence band .With the help of diagram explain effect of impurity concentration on Fermi level of N type semiconductor.

For an electron passing through potential difference V, show that its
wavelength is; 

λ = 12.26/√V A°.

Write Fermi Dirac distribution function. With the help of diagram. Explain the variation of Fermi level with temperature in n-type semiconductor.

Write the Fermi Dirac distribution function and terms in it. What is the probability of an electron being thermally excited to the conduction band in Si at 30 ℃. The band gap energy is 1.12 eV. 

Differentiate between Type-1 & Type- II Superconductors.

Discuss formation of copper pairs and energy gap in superconductor on the basis of BCS theory.

How does the position of fermi energy level changes with increasing doping concentration in p-type semi-conductor ? sketch diagram.

 Explain analysis of crystal structure using Bragg’s X ray spectrometer

Find the minimum energy of neutron confined to a nucleus of size of the order of 10^-14m. Given mass of neutron = 1.675×10^-27kg 

Explain the concept of fermi level. Prove that the Fermi level exactly at the centre of the Forbidden energy gap in intrinsic semiconductor.

In a solid the energy level is lying 0.012 eV below Fermi level. What is the probability of this level not being occupied by an electron 27℃?

Why X-rays are used to study the crystal structure?