Food Engineering Questions and Answers – Unit Operations – Sedimentation and Centrifuge-2

This set of Food Engineering Question Bank focuses on “Sedimentation and Centrifuge-2”

1. In the centrifuge, heavier particles will have a larger radius.
a) True
b) False

Explanation: Since the centrifugal force acting on the heavy particle is more than that on a lighter particle, it will have a larger radius than that of a lighter particle.

2. Statement 1: In both, centrifuge and sedimentation, the terminal velocity of the particle is reached after a certain time.
Statement 2: The formula used for finding out the velocity is the same for both the processes.
a) True, False
b) True, True
c) False, False
d) False, True

Explanation: In only sedimentation, terminal velocity of the particle is reached after a certain time. In centrifuge, the particles are thrown radially outwards and they don’t settle down. Hence there is no terminal velocity. Still, the same formula for finding out the velocity in both the processes is used.

3. Statement 1: The g-number is the ratio of the velocity in a centrifuge to that of the velocity in sedimentation.
Statement 2: The g-number is represented as Z.
a) True, False
b) True, True
c) False, False
d) False, True

Explanation: The g-number is the ratio of the velocity in a centrifuge to that of the velocity in sedimentation. The g-number is represented as Z.

4. Statement 1: In a dairy industry, it is desired to obtain the cream from milk using a centrifuge. Which will stay in the center?
Statement 2: It is desired to have __________ for the above process.
a) Cream, a small neutral zone
b) Milk, a small neutral zone
c) Milk, a large neutral zone
d) Cream, a large neutral zone

Explanation: In a dairy industry, it is desired to obtain the cream from milk using a centrifuge. The cream which is the lighter liquid will stay in the center and milk will splash out radially.
It is desired to have a small neutral zone so as to have a larger central zone where the cream gets accumulated.

5. The area of neutral zone, in a centrifuge is __________
a) Between the heavy and light liquid
b) Next to the light liquid and away from the heavy liquid
c) Next to the heavy liquid and away from the light liquid
d) Above the heavy liquid and below the light liquid

Explanation: The area of neutral zone, in a centrifuge is between the heavy and light liquid.
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6. Statement 1: The radius of neutral zone depends on the radius of the centrifuge.
Statement 2: More is the radius, lesser is the zone of centrifuge.
a) True, False
b) True, True
c) False, False
d) False, True

Explanation: The radius of neutral zone depends on the radius of the centrifuge. More is the radius, more is the zone of centrifuge as it depends on the difference of the radii of the heavy and light zones.

7. Statement 1: Tubular bowl centrifuges can handle slurries.
Statement 2: Tubular bowl centrifuges can be used for 3 phase separation.
a) True, False
b) True, True
c) False, False
d) False, True

Explanation: Tubular bowl centrifuges are used for liquid-liquid separation. Tubular bowl centrifuges can be used for 2 phase liquid-liquid separation only.

8. Basket centrifuge can be used for liquid-liquid separations.
a) True
b) False

Explanation: Basket centrifuge cannot be used for liquid-liquid separations.

9. Which of the following is true?
a) Last traces of alkali or charcoal are removed from oil using the centrifuge
b) Coconut cream obtained by centrifuge is not used in the cosmetic industry
c) All of the mentioned
d) None of the mentioned

Explanation: Both of the mentioned sentences with respect to centrifuge are true.

10. Which food industry is centrifuge NOT used in?
a) Savory and snack foods
b) Sugar Industry
c) Dairy processing
d) None of the mentioned

Explanation: All of the mentioned industries use a centrifuge for their products.

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