Pulverised coal passing through 200 mesh screen has a diameter of 0.074 mm (74 micron). The same passing through 50 mesh screen will have a dia of __________ mm.

Higher is the mesh number, smaller will be the aperture size of the screen. It means that the aperture size of a 200 mesh screen will be smaller than that of 20 mesh screen. This is valid for

A

British standard screens

B

German standard screens (DIN 1171) etc

C

American standard screens (ASTM and Tyler standard screens)

D

All of the above

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 . . . . . . . .
Mineral Dressing in Metallurgy mcq question image

Mineral Dressing in Metallurgy mcq question image

A

1

B

1.8

C

3

D

5.6

Two places P and Q are 440 km apart. Anuj starts from point P towards Q and Dia starts from point Q towards P and they meet after 8 hours. After meeting, Anuj decreased his speed by 9 km/hr and Dia increased her speed by 9 km/hr, then they reached their respective destination at the same time. What is the initial speed of Dia?

A

27 km/hr

B

21 km/hr

C

25 km/hr

D

23 km/hr

Despite having large reserves of coal, why does India import millions of tonnes of coal? 1. It is the policy of India to save its own coal reserves for the future, and import them from other countries for the present use. 2. Most of the power plants in India are coal-based and they are not able to get sufficient supplies of coal from within the country. 3. Steel companies need a large quantity of coking coal which has to be imported. Which of the statements given above is/are correct?

A

1 only

B

2 and 3 only

C

1 and 3 only

D

1, 2 and 3

Which of the following types of particulate matter pollutants are used in the calculation of the Air Quality Index (AQI)? (A) TSP (Total Suspended Particles) (B) PM 10 (Particulate matters of size 10 micron or less) (C) PM 2.5 (Particulate matter of size 2.5 micron or less) (D) PM 1 (Particulate matter of size 1 micron or less) Choose the correct answer from the options given below:

A

(B), (C) and (D) only

B

(A) and (B) only

C

(B) and (C) only

D

(A), (B) and (C) only

For Indian standard (IS) screens, the mesh number is equal to its aperture size expressed to the nearest deca-micron (0.01 mm). Aperture width of IS screen of mesh number 50 will be approximately __________ microns.

A

5

B

50

C

500

D

5000

In India, what is the role of the Coal Controller's Organization (CCO)? 1. CCO is the major source of Coal Statistics in Government of India. 2. It monitors progress of development of Captive Coal/Lignite blocks. 3. It hears any objection to the Government's notification relating to acquisition of coal-bearing areas. 4. It ensures that coal mining companies deliver the coal to end users in the prescribed time. Select the correct answer using the code given below:

A

1, 2 and 3

B

3 and 4 only

C

1 and 2 only

D

1, 2 and 4

Coal is finally pulverised to 200 mesh size for burning in boilers by a

A

Hammer crusher

B

Ball mill

C

Roll crusher

D

Gyratory crusher

Assertion (A): All the mesh currents are necessarily the loop currents but all the loop currents may not be the mesh current. Reason (R): The mesh current is the current which flows only around the perimeter of a mesh.

A

Both (A) and (R) are true and (R) is the correct explanation of (A).

B

Both (A) and (R) are true, but (R) is not the correct explanation of (A).

C

(A) is true, but (R) is false.

D

(A) is false, but (R) is true.

Which of the following statements regarding coal is incorrect? 1. Coal occurs in Gondwana and Tertiary formations in India. 2. Tertiary coal contributes the majority stakes in coal production in India. 3. Jharkhand ranks highest in production as well as reserves of coal in India.

A

1 and 2 only

B

2 only

C

3 only

D

2 and 3 only

Pulverised coal passing through 200 mesh screen has a diameter of 0.074 mm (74 micron). The same passing through 50 mesh screen will have a dia of __________ mm.

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