List of top Material Science and Technology Questions asked in CUET (PG)

The energy gap between the top of the valence band and bottom of the conduction band is called the energy band gap \((E_g)\). Depending upon the materials, the gap can be:

The resistivity of copper metal is \(1.7 \times 10^{-8} \, \Omega \, \text{m}\) and the atomic density of copper is \(8.5 \times 10^{28} \, \text{atoms/m}^3\). The collision time \(\tau\) for electrons in copper is:

Metallic sodium crystallizes in a BCC cubic form with a cube length of \(4.25 \times 10^{-10} \, \text{m}\). The concentration of conduction electrons is:

The kinetic energy of a 3-dimensional gas of \(N\) free electrons at 0 K is:

If the Madelung Constant of NaCl is 1.748, the equilibrium bond distance is \(2.018 \, \text{\AA}\), and the repulsion exponent is \(0.32 \, \text{\AA}\), the cohesive energy of NaCl is:

The concentration of hole-electron pairs in pure silicon at 300 K is \(7 \times 10^{15} \, \text{m}^{-3}\). Antimony is doped into silicon in proportions of \(1 \, \text{atom per} \, 10^7 \, \text{atoms}\), and half of the impurity atoms contribute electrons. The factor by which the number of charge carriers increases due to doping is:

The ratio of charge carrier densities in a pure silicon crystal at \(27^\circ \text{C}\) and \(57^\circ \text{C}\) is 1.25. The energy gap of the semiconductor is:

The electron and hole mobilities in a silicon sample are \(0.135 \, \text{m}^2/\text{V·s}\) and \(0.048 \, \text{m}^2/\text{V·s}\), respectively. If the intrinsic carrier concentration is \(1.5 \times 10^{16} \, \text{atoms/m}^3\), the conductivity at 300 K is:

A pure silicon crystal has \(5 \times 10^{28} \, \text{atoms/m}^3\). It is doped with \(1 \, \text{ppm}\) concentration of pentavalent As. The number of holes is:

The probability that a state is filled at the conduction edge \((E_c)\) is precisely equal to the probability that a state is empty at the valence band edge \((E_v)\). The Fermi level is located at:

A semiconductor has acceptor levels \(57 \, \text{meV}\) above the valence band. The maximum wavelength of light which can excite an electron is:

The energy of a photon of sodium light (\(\lambda = 589 \, \text{nm}\)) is equal to the band gap of a semiconducting material. The minimum energy required to create a hole-electron pair is:

The mean free path of conduction electrons in copper is about \(4 \times 10^{-8} \, \text{m}\). For a copper block, the electric field which can give on average \(1 \, \text{eV}\) energy to a conduction electron is:

A uniform silver wire has a resistivity of \(1.54 \times 10^{-8} \, \Omega \, \text{m}\) at room temperature. When an electric field along the wire is \(1 \, \text{V/m}\), the drift velocity is:

The lowest energy of an electron confined to a 3-dimensional box of length \(0.5 \, \text{\AA}\) is:

Two liters of an ideal gas at a pressure of 10 atm expands isothermally into a vacuum until its total volume is 10 liters. The heat absorbed during the process is:

The percentage increase in magnetic field \(B\) when the space within a current-carrying toroid is filled with aluminium is: (Susceptibility of aluminium \(\chi = 2.4 \times 10^{-5}\)):

The maximum value of permeability \(\mu = 0.126 \, \text{T m/A}\). The maximum relative permeability \(\mu_r\) is:

An ideal solenoid with 40 turns per cm has an aluminium core and carries a current of 2.0 A. The magnetization I developed in the core and the magnetic field B at the center are:(Susceptibility of aluminium \(\chi = 2.3 \times 10^{-5}\)):

A bar magnet made of steel has a magnetic moment of \(2.5 \, \text{Am}^2\) and a mass of \(6.6 \times 10^{-2} \, \text{kg}\). If the density of steel is \(7.9 \times 10^3 \, \text{kg/m}^3\), the intensity of magnetization of the magnet is:

A load of \(4.0 \, \text{kg}\) is suspended from a ceiling through a steel wire of length \(20 \, \text{m}\) and radius \(2.0 \, \text{mm}\). The length of the wire increases by \(0.031 \, \text{mm}\) at equilibrium. The Young’s modulus of steel is: (Take \(g = 9.81 \, \text{m/s}^2\)):

A load of \(4.0 \, \text{kg}\) is suspended from a ceiling fan through a steel wire of radius \(2.0 \, \text{mm}\). The tensile stress developed in the wire when equilibrium is achieved is: (Take \(g = 9.81 \, \text{m/s}^2\)):

Aluminium alloy after failure has a final length of 2.195 in and a final diameter of 0.398 in at the fractured surface. The percentage of elongation and reduction in area is:

A 1.25 cm diameter bar is subjected to a load of 2500 kg. Calculate the engineering stress on the bar in megapascals (MPa):

A 0.500-inch diameter aluminum bar is subjected to a force of 2500 lb. The engineering stress in pounds per square inch (psi) on the bar is: