Category: Objective Questions

Molecular Biology Multiple Choice Questions on “Overview of Protein Synthesis – 1”.

1. Which of the following is the most energetically costly process among the following?
A. Replication
B. Transcription
C. Post transcriptional processing
D. Translation

Answer: D
Explanation: The process of translation is the most conserved of all other cellular processes mentioned above. It is also the most energetically costly process costing over 80% of the cell’s energy in rapidly growing cells.

2. The accurate ordering of amino acids in a polypeptide is determined by the direct interactions between the mRNA template and the amino acid.
A. True
B. False

Answer: B
Explanation: It is unlikely that the accurate ordering of amino acids in a polypeptide is determined by the direct interactions between the mRNA template and the amino acid. This is because the side chains of amino acids have little or no affinity for nucleotides found in the RNAs.

3. Who was the first to propose indirect interaction between mRNA template and amino acids to produce accurate ordering of amino acid in a polypeptide chain?
A. Paul C. Zamecnic
B. James Watson
C. Francis H. Crick
D. Mahlon B. Hoagland

Answer: C
Explanation: Francis H. Crick was the first to propose indirect interaction between mRNA template and amino acids to produce accurate ordering of amino acid in a polypeptide chain in 1955. He suggested that certain adaptor molecules were used to interact with the codons of mRNA and respective amino acids itself acting as a bridging element. This was later demonstrated by Paul C. Zamecnic and Mahlon B. Hoagland that a special class of RNA, the tRNA, was the adaptor molecules as suggested by Crick and thus named transfer RNA.

4. How many major components are used for the process of translation?
A. 1
B. 2
C. 3
D. 4

Answer: D
Explanation: Four major components are used for the process of translation. They are mRNAs, tRNAs, aminoacyl tRNA synthetases and ribosome.

5. Which of the following is not a property of open reading frame?
A. Contiguous
B. Non overlapping
C. Encodes a single protein
D. Starts and ends at either end of the mRNA.

Answer: D
Explanation: The protein coding region of each mRNA is composed of a contiguous, non-overlapping string of codons called open reading frame. Each ORF specifies a single protein and starts and ends at internal sites within the mRNA and thus have distinct start and stop codons used for translation.

6. Both Prokaryote and Eukaryote has one start codon 5’-AUG-3’.
A. True
B. False

Answer: B
Explanation: Eukaryotes have one start codon that is 5’-AUG-3’. Prokaryotes, instead of one, have three start codons: 5’-AUG-3’, 5’-GUG-3’ and 5’-UUG-3’.

7. The start codon has a vital role to play in incorporating the specific amino acids in the peptide chains.
A. True
B. False

Answer: A
Explanation: The start codon plays two important roles in the synthesis of a protein. First, it specifies the first amino acid to be incorporated in the growing polypeptide chain. Second, it defines the reading frame for all the subsequent codons.

8. How many reading frames are applicable in case of translation?
A. 1
B. 2
C. 3
D. 4

Answer: C
Explanation: As the codons are immediately adjacent to each other and because the codons are three nucleotides long, any stretch of mRNA can be translated into three different reading frames. However, once the translation starts the reading frame is fixed as the codons are subsequent to each other.

9. Both prokaryotes and Eukaryotes have one ORF.
A. True
B. False

Answer: B
Explanation: Eukaryotes have only one ORF and are thus known as monocistronic mRNAs. Prokaryotes may have more than one ORF and are thus known as polycistronic mRNAs.

10. Shine – Dalgarno sequence is also known as the __________
A. ORF
B. RBS
C. Stop codon
D. Start codon

Answer: B
Explanation: In prokaryotic mRNA a short sequence is found on the 5’ side where the ribosome binds to the mRNA. This sequence is known as the ribosome binding site (RBS) or the Shine – Dalgarno sequence after the scientist who discovered it.

11. Which component of the rRNA binds to the mRNA?
A. 16S
B. 5S
C. 28S
D. 23S

Answer: A
Explanation: The ribosome binding site is typically located 3 – 9 bp on the 5’ side of the start codon. This sequence is complementary to the sequence located near the 3’ end of the 16S rRNA. The core of the mRNA binding site of the 16S rRNA has a sequence of 5’ – CCUCCU – 3’ and not surprisingly prokaryotic RBS is often the subset of 5’ – AGGAGG – 3’.

12. The phenomenon of translating two a protein by two ribosomes is known as translational coupling.
A. True
B. False

Answer: B

Molecular Biology Multiple Choice Questions on “Methylation of Eukaryotic DNA Controls Gene Expression – 1”.

1. Methylation at which of the following bases is possible within the following oligonucleotides?
A. GAATTC
B. GCGC
C. AGGTTC
D. AAGCTT

Answer: B
Explanation: In eukaryotes, DNA methylation occurs predominantly at CpG dinucleotide sequence. In CpG, the intervening ‘P’ represents the phosphodiester bond linking cytosine- and guanine-containing nucleotides.

2. Which is known to be methylated in eukaryotic cells?
A. Adenine
B. Guanine
C. Cytosine
D. Thymine

Answer: C
Explanation: In eukaryotes only the cytosine residue is methylated. In prokaryotes both adenine and cytosine residue is methylated.

3. Among the following which shows the maximum rate of cytosine methylation?
A. Insects
B. Worms
C. Animals
D. Plants

Answer: D
Explanation: Cytosine methylation is relatively rare in lower eukaryotes. But the cytosine residue in vertebrates is upto 10% of the total number of cytosine bases are methylated and in plants upto 30%.

4. Which of the following is the prototype of a correctly methylated base?
a)

b)

c)

d)

Answer: A
Explanation: The enzyme DNA methyltransferase mediates the transfer of methyl group to cytosine generating 5-methyl-cytosine. Thus the reaction occurs as-

5. The region of maximum methylation in the genome is predominantly activated.
A. True
B. False

Answer: B
Explanation: The regions in the genomic DNA which has a high number of methylated cytosine are usually transcriptionally inactive. Silencing is thought to be either due to direct inhibition of transcription factors binding as a result of methylated cytosine or the binding of other proteins with methyl-binding domain of the DNA.

6. Prokaryotic methylation occurs at ____________
A. AG
B. TC
C. GT
D. CA

Answer: D
Explanation: Prokaryotic methylation occurs at both adenine and cytosine residue. The main function of DNA methylation in prokaryotes is to provide protection from its own endonucleases. It also plays an important role in mismatch repair.

7. How many types of methylation processes are known in eukaryotic cells?
A. 1
B. 2
C. 3
D. 4

Answer: B
Explanation: There are two types of methylation processes known in eukaryotic cells. They are maintenance methylation and de-novo methylation.

8. De-novo methylation is done in the newly synthesized DNA strand at opposite positions of the methylated sites on the parent strand.
A. True
B. False

Answer: B
Explanation: Maintenance methylation is done in the newly synthesized DNA strand at opposite positions of the methylated sites on the parent strand. In de-novo methylation, addition of methyl groups occurs at totally new positions.

9. Both de-novo methylation and maintenance methylation ensures the methylation pattern is inherited from parent to daughters.
A. True
B. False

Answer: B
Explanation: Maintenance methylation is done in the newly synthesized DNA strand at opposite positions of the methylated sites on the parent strand. The maintenance activity ensures that the two daughter DNA molecules retain the methylation pattern of the parent molecule.

10. Methylation of cytosine increases the transition mutation of cytosine to __________
A. Guanine
B. Adenine
C. Thymine
D. Adenine and thymine

Answer: C

Molecular Biology Multiple Choice Questions “Overview of DNA Repair”.

1. What is the correct definition of excision repair?
A. Repair of a single damaged nucleotide
B. Repair of a damaged oligonucleotide
C. Removal of a single damaged nucleotide
D. Removal of a damaged oligonucleotide

Answer: C
Explanation: In the excision repair damaged nucleotide is not repaired but removed from the DNA. The other undamaged strand serves as the template for reincorporation of the correct nucleotide by DNA polymerase.

2. How many types of excision repair systems are known?
A. 1
B. 2
C. 3
D. 4

Answer: B
Explanation: There are two types of excision repair systems. One involves the removal of only the damaged nucleotide. The other involves the removal of a short stretch of single stranded DNA containing the lesion.

3. Why recombinational repair system is called double strand break repair?
A. Both strands are broken
B. One strand is broken
C. No strand is broken
D. Both strand act as template

Answer: A
Explanation: Recombinational repair system is used when both strands are damaged such as when the DNA is broken. In such situation one strand cannot serve as a template for the repair of the other.

4. Which enzyme is activated during double stranded break?
A. DNA polymerase
B. Translesional polymerase
C. RNA polymerase
D. Klenow fragment

Answer: B
Explanation: In double strand break repair when damaged bases block progression of a replicating DNA polymerase a special translesional polymerase copies the bases across the damaged site. This process does not depend on base pairing between the template and the newly synthesized DNA strand.

5. What is the main enzyme that plays a major role in formation of thymine dimer?
A. DNA glycosylase
B. DNA photolyase
C. DNA gyrase
D. DNA ligase

Answer: B
Explanation: In photoreactivation DNA photolyase captures energy from light and uses it to break the covalent bond linking the adjacent pyrimidines. In this process the damaged bases are mended directly.

6. Which two Uvr component molecules scan the DNA during nucleotide excision repair?
A. UvrC, UvrA
B. UvrA, UvrB
C. UvrB, UvrC
D. UvrD, UvrA

Answer: B
Explanation: In nucleotide excision repair complex of two UvrA and UvrB molecules scan the DNA with two UvrA subunits being responsible for detecting the distortions to the helix. Upon encountering a distortion, UvrA exits the complex and create a single stranded bubble with UvrB.

7. After creation of the bubble which Uvr component are recruited?
A. Uvr B
B. Uvr A
C. Uvr C
D. Uvr D

Answer: C
Explanation: After creation of the single stranded bubble Uvr B recruits Uvr C. Uvr C creates two incisions in the double stranded DNA.

8. Which complex in E. coli performs in translesion synthesis?
A. DNA polymerase IV, DNA polymerase V
B. DNA polymerase II, DNA polymerase III
C. DNA polymerase III, DNA polymerase IV
D. DNA polymerase V, RNA polymerase I

Answer: A
Explanation: DNA polymerase IV (Din B. and DNA polymerase V (Umv C. performs translesional synthesis. Din B and Umv C are members of a distinct family of DNA polymerases found in many organisms known as the family of DNA polymerases.

9. In humans which DNA polymerase is involved?
A. DNA polymerase ƞ
B. DNA polymerase α
C. DNA polymerase β
D. DNA polymerase ν

Answer: A
Explanation: DNA polymerase ƞ correctly inserts two A residues opposite a thymine dimer. The active site of DNA polymerase ƞ is better at accommodating a thymine dimer than is the active site of another translesional DNA polymerase.

10. The genes encoding the translesional polymerases are expressed as part of a pathway known as the SOS response.
A. True
B. False

Answer: A
Explanation: The gene encoding the translesional polymerases are expressed as a part of a repair mechanism known as the SOS pathway. The damage leads to the proteolytic destruction of a transcriptional repressor.

11. In eukaryotes the other name of PCNA is __________
A. Sliding clamp
B. Sliding clamp loader
C. Replicative DNA polymerase
D. Translesional DNA polymerase

Answer: A
Explanation: Sliding clamp which is known as PCNA in eukaryotes, anchors the replicative polymerase to the DNA template. The chemical modification is the covalent attachment to the sliding clamp of a peptide known as ubiquitin in a process known as ubiquitinisation.

12. In SOS repair system cleavage of LexA and UmuD is mediated by ___________
A. RecB
B. RecA
C. RecC
D. UvrA

Answer: B
Explanation: LexA and UmuD complex is cleaved by a protein called RecA. This process is activated by single stranded DNA resulting from DNA damage.

13. What are the two fundamental components of NHEJ?
A. KU70, KU80
B. KU50, KU70
C. KU40, KU50
D. KU30, KU40

Answer: A
Explanation: KU70 and KU80 are the most fundamental components of NHEJ. They constitute heterodimers that binds to the DNA ends.

14. NHEJ is ubiquitin independent in eukaryotic organisms.
A. True
B. False

Answer: B
Explanation: NHEJ mechanism is ubiquitin dependent in eukaryotic organisms. The occurrence of NHEJ in prokaryotic cells is less frequent and is predominantly found in eukaryotic cells.

15. In the following compounds which are involved in nucleotide excision repair?
A. UvrA, UvrB, UvrC
B. UvrC, UvrD
C. Uvr C, XPA, XPD
D. XPA, XPC, XPD, XPG

Answer: D

Energy Engineering Multiple Choice Questions on “Calorific Value of Fuels – 1”.

1. The amount of heat liberated by complete combustion of unit quantity of fuel is known as ________
A. Agitation
B. Combustion
C. Calorific value
D. Thermogenesis

Answer: C
clarification: when fuels are burnt, heat is produced. It can also be defined as the amount of heat produced on complete burning of 1gm of fuel. SI unit of calorific value is kJ/g. The chemical reaction is typically hydrocarbon or other organic molecule reacting with oxygen to form carbon dioxide and water and release heat.

2. What is the significance of calorific value?
A. Helps in deciding which fuel is good
B. Helps in locating fuel
C. Helps in deciding ignition temperature
D. Helps in deciding fire point

Answer: A
clarification: The different fuels have different calorific values, i.e. different fuels produce different amount of heat in heat on burning. The calorific value of fuel helps us to decide that which fuel is good for us. This is done by comparing the calorific values of fuels with each other. Usually, a fuel having higher calorific value is considered to be a good fuel.

3. Which gas has the highest calorific value among given option?
A. Oxygen
B. Helium
C. Hydrogen
D. Nitrogen

Answer: C
clarification: Hydrogen gas has the highest calorific value of 150KJ/g among all. So, hydrogen gas is considered is considered to be an extremely good fuel. However, hydrogen gas is not used as a fuel in homes and industries. Reason is hydrogen is highly combustible and it burns with explosion when lighted, its transportation from place to place is very difficult, and the cost of production of hydrogen is very high.

4. How much percent of hydrogen gas does methane contain?
A. 25%
B. 50%
C. 68%
D. 85%

Answer: A
clarification: Methane contains 25% of hydrogen. Since the calorific value of fuels depends on the percentage of hydrogen present in them. So the fuels which have higher percentage of hydrogen will have higher calorific value as compared to those fuels which have lower percentage of hydrogen.

5. Which calorimeter is used to find calorific values of solid and liquid fuels?
A. Boy’s calorimeter
B. Bomb calorimeter
C. Junker’s calorimeter
D. Calvet-type calorimeter

Answer: B
clarification: The calorific value of solid of solid and liquid fuel is defined as the amount of heat liberated by complete combustion of unit mass of fuel. In SI unit s it is expressed in kJ/kg. A bomb calorimeter is a type of constant volume calorimeter used in measuring heat of combustion of particular reaction. Bomb calorimeters have to withstand the large pressure within the calorimeter as the reaction is being measured.

6. Which calorimeter is used to find calorific values of gaseous fuels?
A. Bomb calorimeter
B. Junker calorimeter
C. Adiabatic calorimeter
D. Isothermal titration calorimeter
View Answer

Answer: B
clarification: The calorific values of gaseous fuel are defined as the amount of heat liberated by complete combustion of unit volume of fuel. SI unit is KJ/m³. This calorimeter works on principle of burning of a known volume of gas an imparting the heat with maximum efficiency to steadily flowing water and finding out the rise in temperature of a measured volume of water.

7. The calorific value of all organic compounds has the sign corresponding to a ________
A. Exothermic reaction
B. Endothermic reaction
C. Single displacement reaction
D. Synthesis reaction

Answer: A
clarification: The calorific value of all organic compounds has the sign corresponding to an exothermic reaction. Because the double bond in molecular oxygen is much weaker than other double bonds or pairs of single bonds, particularly those in combustion products carbon dioxide and water, conversion of the weak bonds in o₂ to the stronger bonds in CO₂ and H₂O releases energy as heat.

8. What value of a substance, usually a fuel or food is the amount of heat released during the combustion?
A. Energy value
B. Flash point value
C. Fire point value
D. Auto ignition
View Answer

Answer: A
clarification: Energy value (heating value or calorific value) of a substance, usually a fuel or food is the amount of heat released during the combustion of a specified amount of it. The energy value is characteristic for each substance. It is measured in units of energy per unit of the substance, usually mass, such as Kj/Kg, KJ/mol, and kcal/kg.

9. What accounts for the presence of water in the exhaust leaving as vapor?
A. Gross calorific value
B. Flash point value
C. Ignition temperature value
D. Net calorific value
View Answer

Answer: A
clarification: Gross heating value accounts for water in the exhaust leaving as vapor, and includes liquid water in the fuel prior to combustion. This value is important for fuels like wood and coal, which will usually contain some amount of water prior to burning.

10. What is the factor on which, difference between the two heating values of fuel depends on?
A. Physical properties
B. Reactants
C. Chemical composition
D. Products

Answer: C
clarification: The difference between the two heating values depends on the chemical composition of the fuel. In the case of pure carbon or carbon monoxide, the two heating values are almost identical, the difference being the sensible heat content of carbon dioxide between 150^oC to 25^oC.

Energy Engineering Multiple Choice Questions on “Soot Blowers”.

1. The method of removing soot from the power plant machineries is known as _________
A. Soot cleansing
B. Centrifugation
C. Soot blowing
D. Bioleaching

Answer: D
clarification: The products of combustion cling to the water tubes, economizer tubes, air preheater tubes and super heater tubes. This lowers the efficiency of the plant by reducing heat transfer. So, regular removal of soot or dust is necessary this method is known as soot blowing.

2. Why nozzle tubes are provided in the soot blowers?
A. To moistures the dust
B. To admit high pressure steam
C. To blow away the soot
D. To suck in the dust and exhaust it at high pressure

Answer: B
clarification: The usual form for the smaller boilers is a dead-end tube projecting through the setting and extending into the tube banks. A number of small lateral nozzles are provided and the external head is arranged so that high pressure steam can be admitted to the tube and at the same time the tube is rotated around its axis.

3. Which type of blower advances into the furnace, cleans and comes back?
A. Wall blower
B. Retractable blower
C. Air heat blower
D. Insert able kinetic blower

Answer: B
clarification: Soot blower consists of a set of tubes fitted with nozzles carrying high velocity jet of steam or air. In the hotter parts of the boiler, the blower advances into the furnace, cleans the heat transfer surfaces and comes back. This type of soot blower is known as retractable soot blower.

4. Why are there number soot blower units in large blower?
A. To obtain high efficiency
B. To clean the boiler in short amount of time
C. To clean adequately
D. For easy replacement
View Answer

Answer: C
clarification: Steam jets clean soot from heating surface in their proximity, but the action is limited in extent in a close array such as tube banks; hence several units may be needed to clean the boiler adequately. It is quite common to see 8 to 16 units in a large boiler.

5. Why operating heads of soot blowers are automated?
A. Because they are tedious to operate manually
B. Because they cannot be handled at once
C. Because they are positioned at different parts of machine
D. Because it is quicker by automation
View Answer

Answer: A
clarification: Soot blowers are tedious to operate manually, and since must not all be operated simultaneously, the operating heads are electric motor powered and operated by remote control on an automatic sequential basis.

6. Why on some boilers the draft system controls have to be positioned abnormally in soot blowers?
A. To avoid the soot being blown back into boiler
B. To get a good grip for blowing out the soot from the boiler
C. due to lack of space in the boiler
D. To avoid the heat of boiler affecting the soot blowers

Answer: A
clarification: On some boilers the automatic draft system controls have to be positioned for abnormally high draft before beginning the soot blowing operation; otherwise the release of stem into the setting may blow soot and smoke into the boiler room.

7. In which state would be the soot blower when it’s not in use?
A. Dry and cooled
B. Dry and uncooled
C. Wet and cooled
D. Dry and hot

Answer: B
clarification: When not in use the soot blower tube of the system would be dry and uncooled, and subject to gas temperatures. Even with alloy tubes the deterioration is relatively rapid on units normally experiencing high gas temperatures.

8. What is the advantage of using retractable soot blower?
A. Has high blowing capacity compared to steam and wall blowers
B. Protects from high temperatures when not in use
C. Consumes less amount of electricity
D. Produces less amount of noise

Answer: B
clarification: Retractable blower, though more expensive initially, have the advantage of protection from high temperature when not in use. Also, using only two travelling nozzles, the jet can be larger without excessive steam drain, and the projected blast distance is greater.

9. Why is it necessary to observe temperature drops in the soot blower?
A. To avoid net loss
B. To avoid the soot getting struck in soot blower
C. To avoid over usage
D. To avoid overconsumption of electricity

Answer: A
clarification: It is necessary to observe temperature drops routinely. Obviously if the temperature drops 24°C after blowing, the interval might well be decreased, where as if 12°C were observed; it could represent a net loss because the value of the steam used was more than that of the increment of flue gas heat.

10. Is there a chance of fire due to the accumulation soot inside the boiler.
A. True
B. False
View Answer

Answer: A
clarification: A soot fire can be damaging to a boiler because it can cause localized hotspots to occur in the tubes. These hotspots may reach temperatures that weaken the materials of the tubes. Soot blowers reduce the risk of soot fires and their resulting damage.

Energy Engineering Multiple Choice Questions on “Lubrication System, Intake and Exhaust Systems”.

1. Why does a large diesel engine plant require air?
A. To support combustion
B. To remove dust particles
C. To blow out fumes
D. To run the engine

Answer: A
clarification: A large diesel engine plant requires about 0.076 m³/min to 0.11m³/min of air per KW of power developed inside the engine. Air contains lot of dust; hence it is necessary to remove the dust content in the atmospheric air.

2. What happens if atmospheric temperature is too low?
A. Engine misfires at low loads
B. Engine consumes more amount of fuel
C. Engine gets struck up
D. Exhaust produced comparatively more

Answer: A
clarification: The air system contains an intake manifold located outside the building with filter to catch dirt which would otherwise cause excessive wear in the engine. If the atmospheric temperature is too low, engine misfires at low loads and hence it is necessary to install a heating element using exhaust gas.

3. What is used in engines to reduce the noise at the exhaust?
A. Noise dampers
B. Baffles
C. Silencers
D. Composite foam
View Answer

Answer: C
clarification: Engine sound during operation may be transmitted back through the air intake systems to the outside air. In such cases a silencer is provided between the engine and the intake. It is a light weight steel pipe.

4. In which type of dust filter used in engine is the air swept over or through the pool of oil??
A. Oil bath type
B. Dry-type
C. Soot blower
D. Bessel filter

Answer: A
clarification: in oil bath type of filter the air is swept over or through a pool of oil. The dust particles become coated to the oil. The air is then passed through the filter, which retains the oil coated dust particles.

5. Which type of filter used in engine is made up of cloth, felt and glass wool?
A. Dry-type
B. Oil-bath type
C. Soot blower
D. Bessel filter

Answer: A
clarification: Dry type of filter is made up of cloth, felt and glass wool etc. the filters catch dirt by causing it to cling to the surface of filter material. The capacity of such filters drops progressively when they are in use. The cleaning is done by amount of air used by the engines and dust concentrate in it.

6. What is muffling?
A. Reducing vibration
B. Increasing the flow of gas
C. Reducing noise
D. Filtering the exhaust air
View Answer

Answer: C
clarification: Muffling is the process of reducing the noise. The exhaust system must carry approximately 0.23m³/min-0.30m³/min of gases per kilowatt developed, at the average exhaust temperature. Muffling of the exhaust noise is done by using silencers located outside building.

7. Exhaust pipe is designed carefully in order to carry toxic gases away from the user machine.
A. True
B. False

Answer: A
clarification: An exhaust pipe must be carefully designed to carry toxic and noxious gases away from the users of the machine. It is done so because the gases produced may affect the human being in health wise as well as the environment.

8. Why is lubrication system important in the engine?
A. To improve fuel efficiency
B. To provide cooling
C. To reduce the disturbance
D. To help move the fuel easily

Answer: C
clarification: Due to the presence of friction, wear and tear of the engine parts takes place reducing the engine life. The lubricant introduced forms a thin film between the rubbing surfaces and prevents metal to metal contact.

9. In which type of lubrication method are splash rods used?
A. Full pressure lubrication
B. Mechanical lubrication
C. Force feed lubrication
D. Spray lubrication
View Answer

Answer: A
clarification: In full pressure lubrication splash rods equipped. An oil pump supplies lubricating oil to many parts of the engine through duct system and to the crank shaft through drilled holes. The cylinder walls are lubricated by oil mist that is slung outward by the splash rod connected to flywheel from pool of oil.

10. Why is oil cleaning is necessary in the engine?
A. For continuous reliable operation
B. To cool down the oil
C. To reduce the viscosity of oil
D. To increase thickness of oil
View Answer

Answer: A
clarification: For continuous reliable operation attention should be given to oil cleaning. For this purpose filters with centrifuges or chemical action have been employed. Mechanical filters include cloth bags, wool, felt pads, paper discs and cartridge of porous material.

11. Rough cleaning of oil in engine is done through passing the oil through?
A. Paper discs
B. Nozzle
C. Felt pads
D. High speed centrifuges

Answer: D
clarification: Rough cleaning of oil is done by passing oil through high speed centrifuges. Centrifuges can be done by periodic centrifuging of the entire lubricating oil or by continuous cleaning of a small fraction of it by splitting the oil from main flow and returning back to main stream.

12. Oil is cooled before passing it to the engine.
A. True
B. False

Answer: A
clarification: Oil should be heated before passing it through the centrifuge and then it is cooled before supplying it to the engine. As heat is developed due to friction between the moving parts, the cooling is done by using water from the cooling tower.