Mechanical Operations Questions and Answers – Particle Size

This set of Mechanical Operations Multiple Choice Questions & Answers (MCQs) focuses on “Particle Size”.

1. What is Φs?
a) Sphere
b) Cubicity
c) Sphericity
d) Void age
View Answer

Answer: c
Explanation: Φs is defined as the measure of the roundness of a sphere, it is also the ratio of the surface area of same volume particle and the surface area of particle.

2. For a spherical particle of diameter Dp, Φs is ____
a) 0
b) 0.5
c) 1
d) 2
View Answer

Answer: c
Explanation: As the particle is totally spherical the Sphericity is always 1, for a sphere of diameter Dp, Φs = 1.

3. For any non-spherical particle, Sphericity is defined as _____
a) 6Vp/DpPs
b) 6Vp/PsSp
c) Vp/DpSp
d) 6Vp/DpSp
View Answer

Answer: d
Explanation: Sphericity for any non-spherical particle is defined as 6Vp/DpSp, where Dp is the diameter and Vp and Sp are volume and surface area respectively.
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4. For a crushed material, Φs lies between _____
a) 0.6 to 0.8
b) 1 to 2
c) 1.2 to 1.8
d) 1.6 to 1.8
View Answer

Answer: a
Explanation: As per the empirical calculations and the final results obtained from various experimental values the Φs is calculated to be between 0.6 and 0.8.

5. For cubes and cylinders, what is Φs?
a) 0.65 and 0.50
b) 0.81 and 0.87
c) 0.660 and 0.556
d) 13.2 and 12.3
View Answer

Answer: b
Explanation: For cubes and cylinders for which the length L equals to the diameter, equivalent diameter is greater than L, Φs would be 0.81 and 0.87.
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6. Which of the following gives the total volume of the particles?
a) m/Pp
b) Dp/ Pp
c) Mv/Pp
d) Mv/Dp
View Answer

Answer: a
Explanation: The total volume of the particles is given by m/Pp, where m is the total mass of the sample and Dp is the diameter of the particle.

7. Which of the following gives the number of particles?
a) mVp/Pp
b) Dp/ Pp
c) m/PpVp
d) Mv/Dp
View Answer

Answer: c
Explanation: The total number of the particles is given by m/PpVp, where m is the total mass of the sample, Dp is the diameter and Vp is the volume of particle.
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8. Which of the following gives the total surface area of the particle?
a) N*Sp
b) Vp*Sp
c) Sp/Dp
d) Sp/Vp
View Answer

Answer: a
Explanation: The total surface area of the particle is given by A = N*Sp, where N is the number of the particles and Sp is the surface area of individual particle.

9. The two basic methods of analysis are ______
a) Cumulative and Affirmative
b) Cumulative and Frequency
c) Frequency and Affirmative
d) Affirmative and Conservative
View Answer

Answer: b
Explanation: The two basic method of analysis of screening are Cumulative and Frequency plot techniques, one uses particle size while other one uses screen size.
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10. What is NPr?
a) Pradtl Number
b) Peclet Number
c) Priyang Number
d) Prag Number
View Answer

Answer: a
Explanation: The Prandtl number (Pr) is defined as the ratio of momentum diffusivity to thermal diffusivity i.e. [CPµ/K].

Sanfoundry Global Education & Learning Series – Mechanical Operations .

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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