If 'Δx' represents adherent oxide layer thickness and 't' is time, which of the following curves represents diffusion controlled oxidation kinetics? <img src="/images/question-image/metallurgical-engineering/metallurgical-thermodynamics-and-kinetics/1684343354-M2-B-18-36.PNG" title="Metallurgical Thermodynamics and Kinetics mcq question image" alt="Metallurgical Thermodynamics and Kinetics mcq question image">

Indifference curves relating to supply of labour have a number of properties some of which are mentioned below
1. Indifference curves are downward slopping
2. Indifference curves are upward slopping
3. Higher indifference curves indicate lower levels of utility
4. Higher indifference curves indicate higher levels of utility
5. Indifference curves do not intersect
6. Indifference curves intersect
7. Indifference curves are concave to the origin
8. Indifference curves are convex to the origin
Which among the following properties are not true?

A

1, 2, 3, 4

B

2, 6, 7, 8

C

1, 3, 5, 7

D

2, 3, 6, 7

Select the correct plot of Gibbs free energy (G) Vs. Temperature (T) for a single component system from the following:

A

P

B

Q

C

R

D

S

If k is the rate constant for a reaction and T is the absolute temperature in the given figure, the activation energy for the reaction is . . . . . . . . J/K mole.

A

1000

B

2000

C

4155

D

8314

Consider the figures of a metal ball and a metal ring given below.
The metal ball can just pass through the hole of a metal ring formed out of a strip. When the ball is heated it gets stuck. But when the metal is heated

A

The ball can still pass through the ring as diameter expands on heating

B

The ball gets stuck because of the diameter of the hole decrease on expansion

C

The ball will still pass through because the hole diameter does not change

D

The ball will pass through because there is no change in the ring

A piston containing an ideal gas is originally in the state X (see figure). The gas is taken through a thermal cycle X → Y → X as shown

The work done by the gas is positive, if the direction of the thermal cycle is

A

clockwise

B

counter-clockwise

C

neither clockwise nor counter-clockwise

D

clockwise from X → Y and counter-clockwise from Y → X

The following characteristic curves (P, Q, R, S) pertain to rotary drilling in rock.

Title of the curve
I : Torque versus RPM
II: Rate of penetration versus uniaxial compressive strength of rock
III : Rate of penetration versus weight on bit
IV : Specific energy versus weight on bit
Match the curves with their titles

A

P-III, Q-IV, R-II, S-I

B

P-II, Q-IV, R-I, S-III

C

P-IV, Q-III. R-II, S-I

D

P-I, Q-III, R-II, S-IV

Consider the following statements regarding the importance of diffusion and choose the correct answer:
1. The exchange of gases takes place by the principle of dependent diffusion
2. The process of diffusion is involved in transpiration of water vapours
3. The ions are absorbed by the simple diffusion during passive salt uptake
4. Diffusion is an effective means of transport of substances over a very short distance and helps in the translocation of food materials

A

1, 3 and 4 are true

B

1 and 4 are true

C

1, 2 and 3 are true

D

2, 3 and 4 are true

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

c1 = 0.45, c2 = 0.05

B

c1 = 0.5, c2 = 0.4

C

c1 = -0.05, c2 = 0.45

D

c1 = 0.1, c2 = 0.9

Thin layer of material B (of total amount m) is plated on the end faces of two long rods of material A. These are then joined together on the plated side (see the figure below) and heated to a high temperature. Assuming the diffusion coefficient of B in A is D, the composition profile CB along the rod axis x after a time t is described by

A

$${C_B} = \frac{m}{{2\sqrt {\pi Dt} }}\exp \left$$

B

$${C_B} = \frac{m}{{2\sqrt {\pi Dt} }}erf\left$$

C

$${C_B} = \frac{m}{{2\sqrt {\pi Dt} }}\left$$

D

$${C_B} = \frac{m}{{2\sqrt {\pi Dt} }}t$$

The boundary layer thickness at a distance of l m from the leading edge of a flat plate, kept at zero angle of incidence to the flow direction, is O.l cm. The velocity outside the boundary layer is 25 ml sec. The boundary layer thickness at a distance of 4 m is (Assume that boundary layer is entirely laminar)

A

0.40 cm

B

0.20 cm

C

0.10 cm

D

0.05 cm