This set of Materials Science Multiple Choice Questions & Answers (MCQs) focuses on “Non-steady State Diffusion”.

1. Which of the following law is used to non-steady state diffusion?

a) Fick’s first law

b) Fick’s second law

c) Bragg’s law

d) Charles’s law

View Answer

Explanation: Fick’s second law is used to obtain the diffusion coefficient. Bragg’s law is used in diffraction of light while Charles’s law is used in thermodynamics and is also known as the law of volumes.

2. Which of the following will diffuse the fastest in iron?

a) W

b) C

c) H

d) He

View Answer

Explanation: Hydrogen due to its small size will diffuse the fastest in iron. Carbon also diffuses fast in iron which can be observed in carburizing of steel.

3. Which of the following law is a partial differential equation?

a) Fick’s first law

b) Fick’s second law

c) Bragg’s law

d) Charles’s law

View Answer

Explanation: Fick’s second law is a partial differential law as it is defined as: On the right-hand side we have a partial differential of concentration with respect to time while on the left we have the product of diffusion constant and double partial differential of concentration with respect to the position in space.

4. Which of the following operator is used and on which side of Fick’s second law’s equation?

a) Laplacian operator, right hand side

b) Laplacian operator, left hand side

c) Curl operator, left hand side

d) Gradient, left hand side

View Answer

Explanation: Laplacian operator whose symbol is Δ = ∇2, is used on the right side of the equation of Fick’s law. It replaces the double partial derivative of concentration with respect to space.

5. What is the dimension of d^{2}c/dx^{2}?

a) cm^{3}

b) cm^{5}

c) cm^{-3}

d) cm^{-5}

View Answer

Explanation: The numerator has the dimension of cm

^{-3}and the denominator has a dimension of cm

^{2}. Therefore, the quantity has a dimension of cm

^{-3}/cm

^{2}which gives us cm

^{-5}as the dimension.

6. Concentration gradient varies with time for which of the following processes?

a) Non-steady state diffusion

b) Osmosis

c) Steady state diffusion

d) Filter

View Answer

Explanation: The concentration gradient varies with time for non-steady state diffusion. Meanwhile, it remains constant for steady state diffusion.

7. In non-steady diffusion, a type of atom accumulates or depletes from a region.

a) True

b) False

View Answer

Explanation: As the concentration gradient does not constant with respect to time. So the atoms get accumulated or depleted from certain regions from the system.

8. Gaussian error function in denoted as ef.

a) True

b) False

View Answer

Explanation: Gaussian error function is denoted by the erf and its corresponding values can be found from standard mathematical tables. It is used to find the solution of Fick’s second law.

**Sanfoundry Global Education & Learning Series – Materials Science.**

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