Engineering Questions with Answers - Multiple Choice Questions
Applied Chemistry MCQ – Mechanism of Lubrication
How many mechanisms are there for lubrication?
Explanation: There are three mechanisms are there for lubrication. They are thin film lubrication, thick film lubrication and extreme pressure lubrication. The thick pressure lubrication is also called as fluid film or hydro dynamic lubrication. The thin film lubrication is also called as boundary lubrication.
The thickness of the lubricant film in the hydro dynamic lubrication is about __________
Explanation: In hydro dynamic lubrication, the sliding surfaces are separated completely by applying a thin uniform film of the lubricants between the two surfaces. The thickness of the lubricant film in the hydro dynamic lubrication is about 1000oA.
The liquid lubricants stick due to the _________ property.
a) Surface tension
c) Temperature coefficient
d) Mass of the liquid
Explanation: The liquid lubricants stick due to their physical property called viscosity or stickiness. The liquid lubricant will cover all the irregularities in the slidings and thus it prevents the formation of welded junctions.
The coefficient of friction of unlubricated surface ranges about _________
Explanation: The coefficient of the unlubricated surface is about 0.1 to 1.5. If the lubricant energy is higher, then the energy must be required in large amount to circulate and maintain the viscous lubricant film.
The effectiveness of the hydro dynamic lubrication does not depends upon the ________
a) Design of bearing
c) Rate of rotation of shaft
d) Area of shaft
Explanation: The effectiveness of the hydro dynamic lubrication does not depends upon the area of the shaft. The effectiveness mainly depends upon the design of bearing, load and speed of the shaft rotating.
The continuous fluid film cannot be maintained between the rubbing surfaces under the condition such as high load in boundary lubrication.
Explanation: The continuous fluid film cannot be maintained between the rubbing surfaces under the condition such as high load, slow rate of rotation and very low viscosity oil, etc. These conditions are seen in boundary lubrication.
In boundary lubrication, the coefficient of friction ranges about ______
Explanation: In boundary lubrication, the thickness of the fluid film must be 1000oA. The coefficient of friction is about 0.05 to 0.15. This thin film contains the one or two layers. Thus it is called as thin lubrication or boundary lubrication.
The wear and tear of metal surfaces are involved and _________ are formed in thin lubrication.
a) P-n junctions
b) Welded junctions
d) Thin layers
Explanation: The wear and tear of the metal surfaces is involved and the welded junctions are formed. This also results in friction. These all are formed due to the contact of the surfaces with other leads.
Generation of heat takes place in __________ lubrication.
a) Thin lubrication
b) Thick lubrication
c) Extreme pressure lubrication
d) Boundary lubrication
Explanation: Generation heat and friction are also takes place in extreme pressure lubrication. The thin lubrication is also called as thin lubrication. At high load and pressures, the contact between the surfaces produces the more heat.
The liquid lubricant may be _______
Explanation: The liquid lubricant may be evaporated or decomposed. Due to this, the lubrication becomes ineffective, and the effectiveness can be achieved by adding the extreme pressure additives along with lubricant.