Properties of Engineering Materials MSE 255

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Which type of chemical bond is responsible for the properties of metallic materials?

Molecular bond

Covalent bond

Ionic bond

Metallic bond (correct)

In intrinsic semiconductors, what is left behind in the valence band when electrons are excited to the conduction band?

Protons

Neutrons

Holes (correct)

Electromagnetic waves

What happens to the number of conduction electrons in Silicon as the temperature increases from 20oC to 50oC?

Becomes zero

Decreases

Increases (correct)

Remains constant

Which type of semiconductor conductivity arises from exciting electrons to the conduction band due to a narrow band gap?

Intrinsic conductivity (C) Signup and view all the answers

What determines the width of the energy gap in semiconductors?

Electronegativity difference between elements (A) Signup and view all the answers

Which type of bond strength determines the properties of van der Waals and Hydrogen bonds?

Weakest bond strength (D) Signup and view all the answers

What determines the electrical conductivity in semiconductors?

Charge carrier concentration and carrier mobility (B) Signup and view all the answers

In intrinsic semiconductors, what are the charge carriers?

Both holes and electrons (C) Signup and view all the answers

What is the relationship between electron and hole concentrations in intrinsic semiconductors?

$n_e = n_p$ (B) Signup and view all the answers

What is the formula for electrical conductivity in intrinsic semiconductors?

$\sigma = nq(\mu_e + \mu_h)$ (B) Signup and view all the answers

What parameter influences the electrical conductivity in semiconductors along with charge carrier concentration?

Temperature (C) Signup and view all the answers

Why are holes considered charge carriers in semiconductors?

Due to their positive charge (B) Signup and view all the answers

What is the FERMI located between?

Acceptor and donor energy level (A) Signup and view all the answers

Which of the following is an example of an acceptor atom?

Ga (C) Signup and view all the answers

What is the formula to calculate the magnitude of polarization in a material?

$zqd$ (D) Signup and view all the answers

What causes charge storage in supercapacitors?

Electronic polarization (D) Signup and view all the answers

What does a dipole consist of?

A pair of opposite charges separated by a distance (A) Signup and view all the answers

What does the dielectric constant represent?

Ratio of capacitance with vacuum to dielectric-filled capacitor (A) Signup and view all the answers

What is the fundamental basis for the responses of certain materials to the presence of magnetic fields?

Curie-Weiss Law (A) Signup and view all the answers

Which property is associated with the ability of a material to resist thermal shock?

Expansivity (B) Signup and view all the answers

In the context of electrical properties, what law governs the relationship between voltage and current?

Ohm's Law (D) Signup and view all the answers

Which type of materials exhibit unique behavior at extremely low temperatures by showing zero electrical resistance?

Superconductors (B) Signup and view all the answers

What is the primary focus of optoelectronic mechanism in materials science?

Absorption properties (C) Signup and view all the answers

Which author's work is NOT mentioned as a reference for the course?

Brain S. (D) Signup and view all the answers

What is the formula for conductivity in terms of charge carriers and mobilities?

𝜎 = 𝑛𝑞(𝜇𝑒 + 𝜇ℎ) (A) Signup and view all the answers

At room temperature, how many conducting charges are present per cubic centimeter?

2.51 × 10^13 (A) Signup and view all the answers

What type of semiconductors are used for practical applications?

Extrinsic (C) Signup and view all the answers

What is the result of adding a higher valence dopant to a host material?

Extra electron (n-type) (C) Signup and view all the answers

What is the total number of electrons in the valence band at 0 K?

1.77 × 10^23 (C) Signup and view all the answers

What is the formula for the number of charge carriers in terms of the number of charge carriers at 0 K and the exponential term?

𝑛 = 𝑛𝑜𝑒x𝑝 (B) Signup and view all the answers