# Practice Test: Question Set - 07

**1. Critical Speed (**

*N*) of a ball mill is given by (where_{c}*R*and_{1}*R*are radii of ball mill and the ball respectively)._{2}- (A)

*N*= (1/4π). √(

_{c}*g*/

*R*

_{1}-

*R*

_{2})

- (B)

*N*= (1/2π). √(

_{c}*g*/

*R*

_{1}-

*R*

_{2})

- (C)

*N*= (1/π). √(

_{c}*g*/

*R*

_{1}-

*R*

_{2})

- (D)

*N*= (1/2π). √(

_{c}*R*

_{1}-

*R*

_{2}/

*g*)

**2. General crushing equation is given by**

*d*(*P*/*m*) = -*K*(*d*D̅_{S}/D̅^{n}_{S}). Bond's crushing law is obtained by solving this equation for n = __________ and feed of infinite size.- (A) 1

- (B) 1.5

- (C) 2

- (D) 2.5

**3. Ribbon blenders are exclusively meant for**

- (A) Blending miscible liquids

- (B) Non-flowing powder and thin pastes

- (C) Bath mixing

- (D) Continuous mixing

**4. Removal of activated carbon from glycerine is done by**

- (A) Plate and frame filter

- (B) Rotary vacuum filter

- (C) Batch basket centrifuge

- (D) None of these

**5. Which of the following size reduction equipments employs mainly attrition for ultrafine grinding?**

- (A) Jet mills

- (B) Fluid energy mill

- (C) Micronizer

- (D) All (a), (b) and (c)

**6. The most suitable equipment for removing the fine dust particle (< 1 micron dia.) from air below its dew point will be a/an**

- (A) Bag filter

- (B) Electrostatic precipitator

- (C) Cyclone separator

- (D) Wet scrubber

**7. During agitation of liquids, the**

- (A) Froude number is independent for the curves between power number and
Reynolds number in baffled system

- (B) Power number becomes independent of impellers Reynolds number at
high Reynolds number, but is dependent on the geometry of the impeller

- (C) Froude number is used to account for the effect of surface (e.g.,
the centre vortex) on the power number

- (D) All (a), (b) and (c)

**8. Filtration operation carried out by continuous increase of the inlet pressure of slurry, is called the __________ filtration.**

- (A) Constant rate

- (B) Varying pressure

- (C) Varying rate

- (D) Constant pressure

**9. Chance process is used for the**

- (A) Cleaning of coal

- (B) Concentration of iron ore

- (C) Concentration of pyrites

- (D) Water treatment

**10. The important dimensional group involved in the power requirement calculation in mixing operation is the __________ number.**

- (A) Reynold's

- (B) Froude

- (C) Both (a) & (b)

- (D) Neither (a) nor (b)

**11. The controlling resistance in a rotary drum vacuum filter is the __________ resistance.**

- (A) Piping

- (B) Cake

- (C) Filter medium

- (D) None of these

**12. Separation of particles of various sizes, shapes and densities by allowing them to settle in a fluid is called**

- (A) Classification

- (B) Froth floatation

- (C) Thickening

- (D) Clarification

**13. Theoretical capacity of crushing rolls in tons/hr is given by (where,**

*V*= peripheral velocity, m/sec.*W*= width of rolls, m*Dr*= distance between rolls ρ = density of material to be crushed, kg/m^{3}here,*V*=π*ND*where,*N*= speed of the rolls in rotation per second (rps)*D*= diameter of rolls, m).- (A) 3.6

*V*.

*W*.

*Dr*.ρ

- (B) 3.6

*V*.

*W*. ρ

- (C) 3.6

*W*.

*Dr*.ρ

- (D) 3.6

*V*.

*W*.

*Dr*/ρ

**14. Ore concentration by jigging is based on the difference in the __________ of the particles.**

- (A) Specific gravities

- (B) Wettability

- (C) Shape

- (D) None of these

**15. In a size reduction crushing operation, the feed size is 10 to 50 mm, while the product size is 2 to 10 mm. This is a case of __________ crushing.**

- (A) Primary

- (B) Secondary

- (C) Fine

- (D) Ultrafine

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