Internal Combustion Engines (I.C. Engines) MCQ Questions & Answers

1

The air requirement of a petrol engine during starting compared to theoretical air required for complete combustion is

A) More B) Less C) Same D) May be more or less depending on engine capacity

Discuss

Answer & Solution

Answer: Option B

Solution:

The air requirement of a petrol engine during starting compared to theoretical air required for complete combustion is less

2

Which of the following fuel detonates readily?

A) Benzene B) Iso-octane C) Normal heptane D) Alcohol

Discuss

Answer & Solution

Answer: Option C

Solution:

Normal heptane fuel detonates readily. Octane number equates to the anti-knock qualities of a comparison mixture of heptane and isooctane which is expressed as the percentage of isooctane in heptane and is listed on pumps for gasoline (petrol) dispensed globally.

3

Pour point of fuel oil is the

A) Minimum temperature to which oil is heated in order to give off inflammable vapours in sufficient quantity to ignite momentarily when brought in contact with a flame B) Temperature at which it solidifies or congeals C) It catches fire without external aid D) Indicated by 90% distillation temperature i.e., when 90% of sample oil has distilled off

Discuss

Answer & Solution

Answer: Option B

Solution:

Pour point of fuel oil is the Temperature at which it solidifies or congeals. Pour Point is the temperature at which a liquid becomes semisolid and loses its flowing characteristics. As the paraffin content is high in crude oil, thus it has a high Pour Point.

4

The function of a distributor in a coil ignition system of I.C. engines is

A) To distribute spark B) To distribute power C) To distribute current D) To time the spark

Discuss

Answer & Solution

Answer: Option D

Solution:

The function of a distributor in a coil ignition system of I.C. engines is To time the spark

5

Compression ratio of I.C. Engines is

A) The ratio of volumes of air in cylinder before compression stroke and after compression stroke B) Volume displaced by piston per stroke and clearance volume in cylinder C) Ratio of pressure after compression and before compression D) Swept volume/cylinder volume

Discuss

Answer & Solution

Answer: Option A

Solution:

Compression ratio of I.C. Engines is The ratio of volumes of air in cylinder before compression stroke and after compression stroke

6

The effective inhibitor of pre-ignition is

A) Alcohol B) Water C) Lead D) None of these

Discuss

Answer & Solution

Answer: Option B

Solution:

The effective inhibitor of pre-ignition is water. Pre-ignition is a situation in which the fuel-air mixture in a spark ignition engine ignites before the timed spark, because of contact with a hot surface.

7

The brake power (B.P.) of the engine is given by (where W = Brake load or dead load in newtons, $$l$$ = Length of arm in meters, N = Speed of engine in r.p.m., S = Spring balance reading in newtons, D = Diameter of brake drum in meters and d = Diameter of rope in meters)

A) $${\text{B}}{\text{.P}}{\text{.}} = \frac{{{\text{W}}l \times 2\pi {\text{N}}}}{{60}}{\text{ watts}}$$ B) $${\text{B}}{\text{.P}}{\text{.}} = \frac{{\left( {{\text{W}} - {\text{S}}} \right)\pi {\text{DN}}}}{{60}}{\text{ watts}}$$ C) $${\text{B}}{\text{.P}}{\text{.}} = \frac{{\left( {{\text{W}} - {\text{S}}} \right)\pi \left( {{\text{D}} + {\text{d}}} \right){\text{N}}}}{{60}}{\text{ watts}}$$ D) All of these

Discuss

Answer & Solution

Answer: Option D

Solution:

The brake power (B.P.) of the engine is given by
- $${\text{B}}{\text{.P}}{\text{.}} = \frac{{{\text{W}}l \times 2\pi {\text{N}}}}{{60}}{\text{ watts}}$$
- $${\text{B}}{\text{.P}}{\text{.}} = \frac{{\left( {{\text{W}} - {\text{S}}} \right)\pi {\text{DN}}}}{{60}}{\text{ watts}}$$
- $${\text{B}}{\text{.P}}{\text{.}} = \frac{{\left( {{\text{W}} - {\text{S}}} \right)\pi \left( {{\text{D}} + {\text{d}}} \right){\text{N}}}}{{60}}{\text{ watts}}$$
Where W = Brake load or dead load in newtons, $$l$$ = Length of arm in meters, N = Speed of engine in r.p.m., S = Spring balance reading in newtons, D = Diameter of brake drum in meters and d = Diameter of rope in meters.

8

The ignition of the charge by some hot surface within the engine before the passage of spark is called

A) Pre-ignition B) Detonation C) Ignition delay D) Auto-ignition

Discuss

Answer & Solution

Answer: Option A

Solution:

The ignition of the charge by some hot surface within the engine before the passage of spark is called Pre-ignition. Pre-ignition is a situation in which the fuel-air mixture in a spark ignition engine ignites before the timed spark, because of contact with a hot surface.

9

The air standard efficiency of an I.C. engine is given by (where r = Compression ratio and $$\gamma $$ = Ratio of specific heats)

A) $$1 - {{\text{r}}^{\gamma - 1}}$$ B) $$1 + {{\text{r}}^{\gamma - 1}}$$ C) $$1 - \frac{1}{{{r^{\gamma - 1}}}}$$ D) None of these

Discuss

Answer & Solution

Answer: Option C

Solution:

The air standard efficiency of an I.C. engine is given by $$1 - \frac{1}{{{r^{\gamma - 1}}}}$$
Where,
r = Compression ratio,
$$\gamma $$ = Ratio of specific heats

10

The frictional power (F.P.) is given by

A) F.P. = B.P. - I.P. B) F.P. = I.P. - B.P. C) $${\text{F}}{\text{.P}}{\text{.}} = \frac{{{\text{B}}{\text{.P}}{\text{.}}}}{{{\text{I}}{\text{.P}}{\text{.}}}}$$ D) $${\text{F}}{\text{.P}}{\text{.}} = \frac{{{\text{I}}{\text{.P}}{\text{.}}}}{{{\text{B}}{\text{.P}}{\text{.}}}}$$

Discuss

Answer & Solution

Answer: Option B

Solution:

The frictional power (F.P.) is given by
F.P. = I.P. - B.P.
Friction power - It is defined as the how much power will be used for running the engine. Engine having some friction in gears, chain drives and shafts, matting parts. It consumes some energy from the power.

Internal Combustion Engines (I.C. Engines) MCQ Questions &amp; Answers | Mechanical Engineering

Internal Combustion Engines (I.C. Engines) MCQ Questions & Answers | Mechanical Engineering