Engineering Questions with Answers - Multiple Choice Questions

# Mechanical Operations MCQ’s – Intermediate and Fine Crushers

1 - Question

The ball mill can be best used for which kind of feed?
a) Wet and Dry
b) Coarse and Fine
c) Rocks and Bricks
d) Any kind of feed

Explanation: The ball mill can be used wet or dry grinding facilities the removal of the product, this is the best feed that can be utilized with ball mill.

2 - Question

What is the ratio of length to diameter of tube mill?
a) 4:1
b) 3
c) Both 3 and 4:1
d) 1:2

Explanation: The tube mill is similar to ball mill in the construction and operation and the ratio of length to diameter is 3 or 4:1

3 - Question

Which of the following forces act on the tumbling mill?
a) Tangential force
b) Centrifugal force
c) Circular force
d) Gravitational force

Explanation: Centrifugal forces keeps the ball in contact with the ball mill and with each other during the upward movement.

4 - Question

Which of the following is true, when operating speed is less than critical speed?
a) No grinding
b) Effective grinding
c) Best grinding
d) Bold grinding

Explanation: The speed at which the centrifuging occurs is called as the critical speed and little or no grinding tales place during this phase.

5 - Question

What is the angle of nip for ball mill?
a) 4π2n2 (R-d)/g
b) 4π2n2 (R+d)/g
c) 4π2n2 (R-r)/g
d) 4π2n2 (R-n)/g

Explanation: The angle of nip for a ball mill cos α is defined as 4π2n2 (R-r)/g, Where n is the speed of the rotation of the ball mill.

6 - Question

At critical speed, α = 0 and cos α = 1, what is critical speed?
a) n = nc
b) 2π = nc
c) g = nc
d) gn= nc

Explanation: The critical speed is given when the n i.e. the natural number of revolutions becomes the critical point and critical speed nc.

7 - Question

What does the below equation represent?

a) Natural speed
b) Full speed
c) Optimum speed
d) Critical speed

Explanation: The equation represents critical speed where, g is the gravitational constant and R and r are the radius of ball and the ball mill.

8 - Question

What is percentage of tumbling mill speed?
a) 80 to 100%
b) 65 to 80%
c) 50 to 90%
d) 10 to 50%

Explanation: Tumbling mill runs at 65 and 80 percent of the critical speed, with lower values for wet grinding as well as dry tumbling.

9 - Question

Which of the following uses shearing action?
a) Buhrstone mill
b) Tumbling mill
c) Rod mill
d) Ball mill

Explanation: Size reduction take place by the shearing action, it consists two heavy horizontal wheels placed over one and another.

10 - Question

What is the feed size for a buhrstone mill?
a) Size of peat
b) Size of rock
c) Size of grain
d) Any size