Practice Pakistan's most useful MCQs for competitive exams

Which of the following grinding mills has the horizontally arranged rods as the grinding elements thereby delivering more uniform granular products with minimum fines ?

• (A)  Compartment mill
• (B)  Rod mill
• (C)  Pebble mill
• (D)  Tube mill

Answer

Submitted By :Ali Uppal

Angle of nip of the crushing rolls does not depend upon the_______________?

• (A)  Diameter of the rolls
• (B)  Speed of the rolls
• (C)  Product size
• (D)  Feed size

Answer

Submitted By :Ali Uppal

In screen analysis, the notation +5 mm/-10 mm means particles passing through ____________________?

• (A)  10 mm screen and retained on 5 mm screen
• (B)  5 mm screen and retained on 10 mm screen
• (C)  Both 5 mm and 10 mm screens
• (D)  Neither 5 mm nor 10 mm screen

Answer

Submitted By :Ali Uppal

The critical speed of a trommel (N) is related to its dia D. as _____________________?

• (A)  N ∝ 1/√D
• (B)  N ∝ √D
• (C)  N ∝ D
• (D)  N ∝ 1/D

Answer

Submitted By :Ali Uppal

At low Reynold’s number, the power (P) required for agitating a fluid in a stirred tank becomes independent of inertial forces. In this limit, indicate which of the following relations is satisfied: Po = ρ/ρN3 D5: Power number Re = ρ N D2/μ: Reynold’s number N is the impeller rotational speed, and D is the impeller diameter ?

• (A)  Po ∝ Re-1.0
• (B)  Po ∝ Re0.0
• (C)  Po ∝ Re0.5
• (D)  Po ∝ Re1.0

Answer

Submitted By :Ali Uppal

A _______________ employs a set of screen across a flow channel for the separation of dirt/rust from a flowing liquid stream?

• (A)  Thickener
• (B)  Classifier
• (C)  Strainer
• (D)  Clarifier

Answer

Submitted By :Ali Uppal

Laminar flow region is said to exist during agitation of a liquid in an agitator, when the value of Reynolds number is________________?

• (A)  > 10
• (B)  < 10
• (C)  > 100
• (D)  < 100

Answer

Submitted By :Ali Uppal

_______________ centrifuge is the most suitable for separation of non-friable crystals?

• (A)  Tubular bowl
• (B)  Disc-bowl
• (C)  Perforated horizontal basket continuous
• (D)  Suspended batch basket

Answer

Submitted By :Ali Uppal

In a size reduction crushing operation, feed size is 300 to 1500 mm while the product size is 100 to 300 mm. This is a case of the ________________ crushing?

• (A)  Secondary
• (B)  Fine
• (C)  Primary
• (D)  Ultrafine

Answer

Submitted By :Ali Uppal

Higher is the mesh number, smaller will be the aperture size of the screen. It means that the aperture size of a 200 mesh screen will be smaller than that of 20 mesh screen. This is valid for__________________?

• (A)  British standard screens
• (B)  German standard screens (DIN 1171) etc
• (C)  American standard screens (ASTM and Tyler standard screens)
• (D)  All

Answer

Submitted By :Ali Uppal