List of top Questions asked in GATE Engineering Sciences

A pure Silicon wafer is doped with Boron by exposing it to $B_2O_3$ vapour at an elevated temperature. It takes 1000 seconds to reach a Boron concentration of $10^{20}$ atoms $m^{-3}$ at a depth of $1 \, \mu m$. The time taken to reach the same concentration of Boron at a depth of $2 \, \mu m$ is (in seconds): ................ (rounded off to nearest integer).

The Young’s modulus of a quartz piezoelectric crystal is 100 GPa. The uniaxial stress required to change its polarization by 1% is (give absolute value in GPa) .............. (rounded off to nearest integer).

A one-dimensional nanowire has a linear electron density of $10^8 \, electrons \, cm^{-1}$. The Fermi energy of the system is (in eV) ............ (rounded off to two decimal places). Given: \[ \frac{\hbar^2}{2m} = 0.24 \, (eV)^2 \, s^2 \, kg^{-1} \] where $m$ is the electron mass.

A screw dislocation in a FCC crystal has Burgers vector of $\frac{a}{2}[110]$, where $a$ is the lattice constant. The possible slip plane(s) is/are:

The tensile true stress ($\sigma$) – true strain ($\varepsilon$) curve follows the Hollomon equation: \[ \sigma = 500 \, \varepsilon^{0.15} \ \text{MPa} \] At the maximum load, the work-hardening rate $\left(\frac{d\sigma}{d\varepsilon}\right)$ is (in MPa):

A metal has a certain vacancy fraction at a temperature of 600 K. On increasing the temperature to 900 K, the vacancy fraction increases by a factor of $________________$. Given: $R = 8.31 \ \text{J mol}^{-1}\text{K}^{-1}$, $Q = 68 \ \text{kJ mol}^{-1}$

In a semiconductor, the ratio of electronic mobility to hole mobility is 10. The density of electrons and holes are $10^{15}$ m$^{-3}$ and $10^{16}$ m$^{-3}$, respectively. If the conductivity is $1.6 \ \Omega^{-1}$ m$^{-1}$, then the mobility of holes is $________________ \ (m^2 V^{-1} s^{-1})$. Given: $q = 1.6 \times 10^{-19}$ C

A student performed X-ray diffraction experiment on a FCC polycrystalline pure metal. The following $\sin^2 \theta$ values were calculated from the diffraction peaks: \[ \sin^2 \theta = 0.136,\; 0.185,\; 0.504,\; 0.544 \] However, the student was negligent and missed noting one of the peaks. Which one of the following Miller indices corresponds to the missing peak?

Match the lattice planes and directions (in Column I) with the corresponding Miller indices (in Column II):

Match the hardness test (in Column I) with its indenter type (in Column II):

Axial velocity profile $u(r)$ for an axisymmetric flow through a circular tube of radius $R$ is given as, \[ \frac{u(r)}{U} = \left(1 - \frac{r}{R}\right)^{1/n} \] where $U$ is the centerline velocity. If $V$ refers to the area-averaged velocity (volume flow rate per unit area), then the ratio $V/U$ for $n = 1$ (rounded off to two decimal places) is $________________$.

A stationary circular pipe of radius $R = 0.5$ m is half filled with water (density = 1000 kg/m$^3$), whereas the upper half is filled with air at atmospheric pressure, as shown in the figure. Acceleration due to gravity is $g = 9.81$ m/s$^2$. The magnitude of the force per unit length (in kN/m, rounded off to one decimal place) applied by water on the pipe section AB is $________________$.

In age-hardening of an aluminium alloy, the purpose of solution treatment followed by quenching is to

The magnetization (M) – magnetic field (H) curves for four different materials are given below. Which one of these materials is most suitable for use as a permanent magnet?

The band gap of a semiconducting material is $\sim 2$ eV. Which one of the following absorption (A) vs. energy (in eV) curves is correct?

Figures (i) and (ii) show a binary phase diagram and the corresponding Gibbs free energy (G) vs. composition ($X_B$) diagram, respectively. Figure (ii) corresponds to which one of the temperatures shown in Figure (i)?

Aliovalent doping of $MgCl_2$ in $NaCl$ leads to the formation of defects. Which one of the following is the correct defect reaction?

A water jet (density = 1000 kg/m$^3$) is approaching a vertical plate, having an orifice at the center, as shown in the figure. While a part of the jet passes through the orifice, remainder flows along the plate. Neglect friction and assume both the inlet and exit jets to have circular cross-sections. If $V = 5$ m/s, $D = 100$ mm and $d = 25$ mm, magnitude of the horizontal force (in N, rounded off to one decimal place) required to hold the plate in its position is $________________$.

Water (density = 1000 kg/m$^3$) and alcohol (specific gravity = 0.7) enter a Y-shaped channel at flow rates of 0.2 m$^3$/s and 0.3 m$^3$/s, respectively. Their mixture leaves through the other end of the channel, as shown in the figure. The average density (in kg/m$^3$) of the mixture is $________________$.

The velocity and acceleration of a fluid particle are given as $\vec{V} = (-\hat{i} + 2\hat{j})$ m/s and $\vec{a} = (-2\hat{i} - 4\hat{j})$ m/s$^2$, respectively. The magnitude of the component of acceleration (in m/s$^2$, rounded off to two decimal places) of the fluid particle along the streamline is $________________$.

A hydraulic turbine with rotor diameter of 100 mm produces 200 W of power while rotating at 300 rpm. Another dynamically-similar turbine rotates at a speed of 1500 rpm. Consider both turbines to operate with the same fluid (identical density and viscosity), and neglect any gravitational effect. Then the power (in W, rounded off to nearest integer) produced by the second turbine is $________________$.

Water (density = 1000 kg/m$^3$) flows steadily with a flow rate of 0.05 m$^3$/s through a venturimeter having throat diameter of 100 mm. If the pipe diameter is 200 mm and losses are negligible, the pressure drop (in kPa, rounded off to one decimal place) between an upstream location in the pipe and the throat (both at the same elevation) is $________________$.

Water flows around a thin flat plate (0.25 m long, 2 m wide) with a free stream velocity ($U_\infty$) of 1 m/s, as shown in the figure. Consider linear velocity profile $\left(\frac{u}{U_\infty} = \frac{y}{\delta}\right)$ for which the laminar boundary layer thickness is expressed as $\delta = \frac{3.5x}{\sqrt{Re_x}}$. For water, density = 1000 kg/m$^3$ and dynamic viscosity = 0.001 kg/m·s. Net drag force (in N, rounded off to two decimal places) acting on the plate, neglecting the end effects, is $________________$.

For a potential flow, the fluid velocity is given by $\vec V(x,y)=u\,\hat{\imath}+v\,\hat{\jmath}$. The slope of the {potential line} at $(x,y)$ is

Consider steady incompressible flow of a Newtonian fluid over a horizontal flat plate, as shown in the figure. The boundary layer thickness is proportional to