Engineering Questions with Answers - Multiple Choice Questions

# Mechanical Operations MCQ’s – Crushers

1 - Question

As the size of feed increases, size of product ____
a) Remains same
b) Decreases
c) Increases
d) No effect

Explanation: The larger the size of the feed the larger will be the size of the product, a smaller size reduction is obtained with hard material.

2 - Question

For a ball mill, what will happen to product if the weight of ball increases?
a) Coarser
b) Finer
c) Bigger
d) No change

Explanation: If the mill is charged with heavy balls, the product will be finer, the weight can be increased or the number if ball can also be increased.

3 - Question

As the size of ball increase, the size of product ____
a) Remains same
b) Decreases
c) Increases
d) No effect

Explanation: Balls of smaller diameter give only fine product, but they do not deal effectively with larger particles in the feed.

4 - Question

Increasing the slope of the mill, product becomes ____
a) Coarser
b) Finer
c) Bigger
d) No change

Explanation: Increasing the slope of the mill increases the capacity of the mill because retention time reduced but a coarser product is obtained.

5 - Question

What does increased discharge freedom results in?
a) Coarser product
b) Finer product
c) Bigger product
d) No change

Explanation: Increasing the freedom of discharge of the product has the same effect as slope i.e. it results in coarser products.

6 - Question

At low speeds, ____ Crushing is obtained.
a) High
b) Low
c) Optimum
d) Total

Explanation: At low speeds, the balls simply roll over one another and little crushing is obtained, thus reducing the equality of product.

7 - Question

At high speed, Crushing obtained can be _____
a) Minimum
b) Maximum
c) No effect
d) Optimum

Explanation: At high speed, the balls present in the mills are carried over along the circumference of the mill and thus no crushing or minimum crushing is obtained

8 - Question

What is the minimum speed at which ball mill operates called?
a) Cumulative speed
b) Threshold speed
c) Optimum speed
d) Critical speed

Explanation: The minimum speed at which ball mill operates is called Critical speed, under these conditions no resultant force acts on the mill and crushing is maximum.

9 - Question

What is the angular velocity We?
a) √(D/R)
b) g/R
c) √(g/R)
d) √(H/R)

Explanation: The angular velocity is defined as We = √(g/R) , where R is the radius of the mill less the radius of the critical speed.

10 - Question

As the level in the mill reduces, power consumption ____
a) Remains same
b) Decreases
c) Increases
d) No effect