Mechanical Operations MCQ’s – Properties of Impellers

As particle size is reduced _____
a) Screening becomes progressively more difficult
b) Screening becomes progressively easier
c) Capacity of screen is increased
d) Effectiveness of screen is increased

Answer: a
Explanation: As the undersized is passed through the screen more particles are clotted in the screen which cause screening more difficult.

 The speed of a rotary drum vacuum filter may be about ______ rpm.
a) 1
b) 50
c) 100
d) 500

Answer: a
Explanation: These filters are generally operated at a low speed of 1 revolution per minute as they are involved vacuum.

The most common filter aid is _________
a) Diatomaceous earth
b) Calcium silicate
c) Sodium carbonate
d) Silica gel

Answer: a
Explanation: Diatomaceous also known as kieselguhr, is a naturally occurring siliceous sedimentary rock that is easily crumbled into a fine white to off-white powder.

Mixture can be removed from lubricating oil using _______
a) Tubular centrifuge
b) Clarifier
c) Sparkler filter
d) Vacuum leaf filter

Answer: a
Explanation: As tubular centrifuge involves the centrifugal force solid particles are separated towards the side of the walls and offer good separation.

For separation of sugar solution form settled out mud, we use a ____ filter.
a) Sparkler
b) Plate and frame
c) Centrifugal
d) Rotary drum vacuum

Answer: c
Explanation: Again as particles of mud are small and involves liquid, the centrifuge is the best option to settle particle of mud and separate them

Compressibility coefficient for an absolutely compressibility cake is ___
a) 0
b) 1
c) 0 to 1
d) Infinity

Answer: b
Explanation: Compressibility is a measure of the relative volume change of a fluid or solid as a response to a pressure, for absolute compression it is unity.

The porosity of a compressible cake is _________
a) Minimum at the filter medium
b) Minimum at the upstream face
c) Maximum at the filter medium
d) Same throughout the cake

Answer: a
Explanation: As the filtration forwards the cake is formed, pressure in increased and cause resistance due to which compressibility is minimum.

 A straight line is obtained on plotting reciprocal of filtration rate vs. the volume of the filtrate for ____ flow of filtrate.
a) Compressible cake and laminar
b) Incompressible cake and laminar
c) Compressible cake and turbulent
d) Incompressible cake and turbulentAnswer: b
Explanation: The reciprocal of filtration rate when plotted with volume follows a linear relation having slope m for laminar flow of filtrate.

Answer: b
Explanation: The reciprocal of filtration rate when plotted with volume follows a linear relation having slope m for laminar flow of filtrate.

 The capacity of a belt conveyor depends upon two factors, if one is the cross section of the load the other is the _______ of the belt.
a) Speed
b) Thickness
c) Length
d) Density

Answer: a
Explanation: Capacity follows a direct relation with thickness of belt, as capacity increases the thickness also increases.

For coal, wash ability curve based on the float and sink test based on the ________
a) Density separation
b) Differential wettability
c) Size
d) Volatile matter content

Answer: a
Explanation: wash ability curve based on the float and sink test based on the density separation that enables an assessment to be made of the possibility of cleaning of coal fraction.