Electronic Properties - Materials Science and Non-Metallic Materials - Metallurgical Engineering Previous Year Questions

1

2007 · Metallurgical Engineering · Materials Science and Non-Metallic Materials · Electronic Properties

Metallurgical Engineering (MT) 2007

Match the energy gaps in group-I with the materials in group-II.

Group I	Group II
(P) Diamond	(1) 0.1 eV
(Q) Silicon	(2) 0.7 eV
(R) Gray Tin	(3) 1.1 eV
	(4) 6.0 eV

A

P-1, Q-4, R-3

B

P-2, Q-3, R-1

C

P-3, Q-1, R-2

D

P-4, Q-3, R-1

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2

2009 · Metallurgical Engineering · Materials Science and Non-Metallic Materials · Electronic Properties

Metallurgical Engineering (MT) 2009

p-type semiconductor can be obtained by doping silicon with

A

antimony

B

phosphorous

C

arsenic

D

boron

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3

2009 · Metallurgical Engineering · Materials Science and Non-Metallic Materials · Electronic Properties

Metallurgical Engineering (MT) 2009

Match the properties in Group 1 with the testing techniques in Group 2.

Group 1	Group 2
P. Electrical conductivity	1. Jominy test
Q. Impact energy	2. Izod test
R. Thermal expansion	3. Dilatometry
S. Specific heat	4. Four probe technique
	5. Differential scanning calorimetry

A

P-4, Q-2, R-5, S-1

B

P-5, Q-3, R-2, S-1

C

P-2, Q-1, R-3, S-4

D

P-4, Q-2, R-3, S-5

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4

2010 · Metallurgical Engineering · Materials Science and Non-Metallic Materials · Electronic Properties

Metallurgical Engineering (MT) 2010

Silicon is doped with arsenic (concentration 10²⁰ atoms m^-3). At room temperature, the electron and hole mobilities in Si are 0.14 m² V^-1 s^-1 and 0.05 m² V^-1 s^-1, respectively. The conductivity, in (\(\Omega m\))^-1, at room temperature for Si doped with As is

A

0.11

B

0.96

C

2.24

D

2.72

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5

2011 · Metallurgical Engineering · Materials Science and Non-Metallic Materials · Electronic Properties

Metallurgical Engineering (MT) 2011

The material in which there is conduction primarily by holes is

A

conductor

B

insulator

C

p-type semiconductor

D

n-type semiconductor

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6

2012 · Metallurgical Engineering · Materials Science and Non-Metallic Materials · Electronic Properties

Metallurgical Engineering (MT) 2012

As temperature increases, the electrical resistivities of pure metals (ρm) and intrinsic semiconductors (ρi) vary as follows

A

Both ρm and ρi increase

B

Both ρm and ρi decrease

C

ρm increases and ρi decreases

D

ρm decreases and ρi increases

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7

2014 · Metallurgical Engineering · Materials Science and Non-Metallic Materials · Electronic Properties

Metallurgical Engineering (MT) 2014

As mercury is cooled from room temperature to 3 K, its electrical behaviour changes from that of

A

conductor to insulator

B

semiconductor to insulator

C

conductor to superconductor

D

semiconductor to superconductor

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8

2016 · Metallurgical Engineering · Materials Science and Non-Metallic Materials · Electronic Properties

Metallurgical Engineering (MT) 2016

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 columns correctly represents the listed parameters? Assume same effective mass for electrons and holes.

A

Column 1

B

Column 2

C

Column 3

D

Column 4

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9

2017 · Metallurgical Engineering · Materials Science and Non-Metallic Materials · Electronic Properties

Metallurgical Engineering (MT) 2017

For an intrinsic semiconductor, the room temperature electrical conductivity is 10⁻⁶ Ω⁻¹.m⁻¹. If the electron and hole mobilities are 0.75 and 0.06 m²V⁻¹s⁻¹ respectively, the intrinsic carrier concentration (per m³) at room temperature is:

A

5.1 × 10¹²

B

7.7 × 10¹²

C

8.3 × 10¹²

D

1.1 × 10¹⁴

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10

2018 · Metallurgical Engineering · Materials Science and Non-Metallic Materials · Electronic Properties

Metallurgical Engineering (MT) 2018

For intrinsic Si at room temperature, the electron concentration = the hole concentration = \(1 \times 10^{16} \text{m}^{-3}\), and the electron and hole mobilities are 0.1 and 0.2 \(\text{m}^2 \text{V}^{-1} \text{s}^{-1}\) respectively. What is the room temperature electrical conductivity?
The charge of an electron is \(1.6 \times 10^{-19} \text{C}\).

A

0 \((\Omega\cdot\text{m})^{-1}\)

B

\(1.6 \times 10^{-4} \) \((\Omega\cdot\text{m})^{-1}\)

C

\(3.2 \times 10^{-4} \) \((\Omega\cdot\text{m})^{-1}\)

D

\(4.8 \times 10^{-4} \) \((\Omega\cdot\text{m})^{-1}\)

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11

2020 · Metallurgical Engineering · Materials Science and Non-Metallic Materials · Electronic Properties

Metallurgical Engineering (MT) 2020

A dielectric material is:

A

Electrical conductor

B

Metallic magnet

C

Two coupled electrical conductors

D

Electrical insulator

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12

2020 · Metallurgical Engineering · Materials Science and Non-Metallic Materials · Electronic Properties

Metallurgical Engineering (MT) 2020

Match the elements in Column I with their electronic behaviour given in Column II.

Column I	Column II
(P) Copper	1. Ferromagnetic
(Q) Iron	2. Superconducting
(R) Mercury	3. Semiconducting
(S) Silicon	4. Diamagnetic

A

P-1, Q-2, R-3, S-4

B

P-3, Q-4, R-1, S-2

C

P-4, Q-1, R-2, S-3

D

P-4, Q-3, R-1, S-2

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13

2020 · Metallurgical Engineering · Materials Science and Non-Metallic Materials · Electronic Properties

Metallurgical Engineering (MT) 2020

Zone refining of Si results in residual P content of 0.1 parts per billion by weight. The electrical conductivity of this zone refined Si is ______ Ω⁻¹.m⁻¹ (round off to two decimal places).\n\nGiven:\n1. Avogadro number is 6.02×10²³.\n2. Density of Si is 2.33 g.cm⁻³.\n3. Atomic weight of P is 30.97.\n4. Charge of electron is 1.6×10⁻¹⁹ A.s\n5. Mobility of electron is 0.2 m².V⁻¹.s⁻¹

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14

2023 · Metallurgical Engineering · Materials Science and Non-Metallic Materials · Electronic Properties

Metallurgical Engineering (MT) 2023

Diamond has low

A

electrical conductivity

B

modulus of elasticity

C

hardness

D

thermal conductivity

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15

2025 · Metallurgical Engineering · Materials Science and Non-Metallic Materials · Electronic Properties

Metallurgical Engineering (MT) 2025

An intrinsic semiconductor has conductivity of 100 Ω⁻¹ m⁻¹ at 300 K and 300 Ω⁻¹ m⁻¹ at 500 K.
The band gap of the semiconductor is ______ eV (rounded off to two decimal places).
Given: Boltzmann constant \( k_B = 8.6 \times 10^{-5} \) eV K⁻¹

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