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A simplified energy band-diagram of an intrinsic semiconductor at thermal equilibrium (300 K) is shown. In the accompanying table, which one of the four cloumns correctly represents the listed parameters? Assume same effective mass for electrons and holes.<br><img src="/images/question-image/metallurgical-engineering/physics-of-metals-in-metallurgy/1684344053-M2-B-16-81.PNG" title="Physics of Metals in Metallurgy mcq question image" alt="Physics of Metals in Metallurgy mcq question image"><br>
A
<table class="table-style-1"> <tr> <td rowspan="2">Parameter</td> <td colspan="4">Energy-difference</td> </tr> <tr> <td><strong>Column 1</strong></td> <td><strong>Column 2</strong></td> <td><strong>Column 3</strong></td> <td><strong>Column 4</strong></td> </tr> <tr> <td>Band-gap</td> <td>ΔE<sub>2</sub></td> <td>ΔE<sub>1</sub></td> <td>ΔE<sub>2</sub></td> <td>ΔE<sub>1</sub></td> </tr> <tr> <td>Electron affinity</td> <td>$$\frac{{\Delta {E_1}}}{2}$$</td> <td>ΔE<sub>2</sub> - ΔE<sub>1</sub></td> <td>$$\frac{{\Delta {E_2}}}{2}$$</td> <td>ΔE<sub>2</sub> - $$\left( {\frac{{\Delta {E_1}}}{2}} \right)$$</td> </tr> <tr> <td>Work function</td> <td>ΔE<sub>1</sub> + ΔE<sub>2</sub></td> <td>ΔE<sub>2</sub> - $$\left( {\frac{{\Delta {E_1}}}{2}} \right)$$</td> <td>ΔE<sub>1</sub> - $$\frac{{\Delta {E_2}}}{2}$$</td> <td>ΔE<sub>2</sub> + $$\left( {\frac{{\Delta {E_1}}}{2}} \right)$$</td> </tr></table> Column 1
B
Column 2
C
Column 3
D
Column 4
Correct Answer:
Column 2
An elliptical dislocation loop is gliding on plane ABCD of a single crystal of BCC material as shown in the following figure. It is gliding along the burger vector 'b'. Identify the correct statement.
P. Plane ABCD belongs to the family of (110).
Q. Burger vector 'b' belong to direction.
R. Dislocation has the edge character at point x and the screw character at point z.
S. Dislocation has the screw character at point x
A
P, Q
B
Q, R
C
P, R
D
P, S
The diffusion couple shown below is made from two A-B alloys. The initial compositions of the two alloys are indicated in the diagram. The centreline is at x = 0. The couple is held at an elevated temperature for 40 hours. Diffusivity; D = 3 × 10
-11
m
-2
s
-1
. Assume the diffusion couple to be infinitely long.
Which of the parameters give the composition profile in the following form?
$$C\left( {x,t} \right) + {c_1} + {c_2}\,erf\left( {\frac{1}{{2\sqrt {Dt} }}} \right)$$
A
c<sub>1</sub> = 0.45, c<sub>2</sub> = 0.05
B
c<sub>1</sub> = 0.5, c<sub>2</sub> = 0.4
C
c<sub>1</sub> = -0.05, c<sub>2</sub> = 0.45
D
c<sub>1</sub> = 0.1, c<sub>2</sub> = 0.9
A furnace wall is made of three materials (I, II and III) of equal thickness and having thermal conductivity k
1
k
2
and k
3
respectively. The steady state temperature profile inside each material is shown in the figure. Thermal conductivities of the materials will vary as
A
k<sub>1</sub> > k<sub>2</sub> > k<sub>3</sub>
B
k<sub>2</sub> > k<sub>1</sub> > k<sub>3</sub>
C
k<sub>3</sub> > k<sub>1</sub> > k<sub>2</sub>
D
k<sub>3</sub> > k<sub>2</sub> > k<sub>1</sub>
A schematic of X-ray diffraction pattern of a single phase cubic polycrystal is given below. The miller idices of Peak A is
A
210
B
220
C
222
D
310
A furnace wall consists of four layers of different materials, M
1
, M
2
, M
3
and M
4
. If the layers are of equal thickness and the steady state temperature profiles is as shown below, then the material with the lowest thermal conductivity is
A
M<sub>1</sub>
B
M<sub>2</sub>
C
M<sub>3</sub>
D
M<sub>4</sub>
Match the heat treatment for an eutectoid steel shown in the TTT diagram below (as P, Q, R and S) with the resulting microstructure listed below:
1. Fine pearlite
2. martensite
3. Bainite
4. Coarse pearlite
A
P-1, Q-2, R-4, S-3
B
P-4, Q-1, R-3, S-2
C
P-2, Q-1, R-3, S-4
D
P-1, Q-4, R-3. S-2
The figure below shows the cumulative size distribution of particles of a crushed mineral. 10 kg of this material is first passed through a sieve of size 400 micron and then through a sieve of size 300 micron. The weight of mineral (in kg ) that is retained on the 300 micron sieve is . . . . . . . .
A
1
B
1.8
C
3
D
5.6
An alloy of overall composition, X
B
= 0.7 was equilibrated at temperature T
1
. Microstructural analysis showed two phases, (α and β, and that the phase fraction of β was 0.75. Given that the equilibrium composition of β at Ti is 0.9 as shown in the phase diagram below, the maximum solubility of B in α (in mole fraction) at this temperature is . . . . . . . .
A
0.05
B
0.10
C
0.50
D
0.85
From a 2 m × 1.2m sheet, squares are Cut out from each of the four comers as shown in the figure and then the sides are bent to form an open box. The maximum possible volume (in m
3
) of the box is
A
0.14
B
0.26
C
0.54
D
0.82
Engineering stress-strain curve for a metal under two conditions. A and B, are shown is the following figures. Identify the correct statement.
A
The resilience of the material is the same in conditions A and B
B
The resilience of the material is higher in condition B than in condition A
C
The toughness of the material is higher in condition A than in condition B
D
The toughness of the material is higher in condition B than in conditon A
