250+ TOP MCQs on I.C. Engine Components and Answers

This set of Farm Machinery Multiple Choice Questions on “I.C. Engine Components”.

1. Rapid explosion of air-fuel mixture within the cylinder, when ignited by a spark is known as _______
a) constant heat combustion
b) constant pressure combustion
c) constant volume combustion
d) cut off ratio

Answer: c
Explanation: There are two ways in which combustion takes place in the cylinder. When there is a rapid explosion of air- fuel mixture within the cylinder when it is ignited by spark, is called constant volume combustion and when there is a slow burning when the fuel is injected into highly compressed heated air, then it is known as constant pressure combustion.

2. Which is largest piston driven aircraft having 36 cylinders?
a) DKW
b) Lycoming R-7755
c) Saab 92
d) Pratt and Whitney R-4360

Answer: b
Explanation: DKW and Saab 92 are examples of large cars having two cylinders or two-stroke engines. Pratt and Whitney R-4360 is an example of an aircraft having 28 cylinders. Lycoming R-7755 is an aircraft which had 36 cylinders, making it the largest piston driven aircraft.

3. Which of the following is an indicator of the combustion speed of diesel fuel and compression needed for ignition?
a) Cetane Number
b) Octane Number
c) Calorific Value
d) Pre-Ignition

Answer: a
Explanation: Octane number is the ignition quality of petrol. Calorific value is the energy contained by fuel determined by complete combustion. Pre-ignition is the premature combustion of the fuel air mixture.

4. A four-stroke diesel engine operating at 1200 rpm uses 0.1 kg of fuel in 5 minutes and has the brake specific fuel consumption equals to 0.1910 kgBHPh. Calculate the torque developed.
a) 6.5 kg-m
b) 8 kg-m
c) 7.5 kg-m
d) 5 kg-m

Answer: c
Explanation: N = 1200/2 = 600
BHP = 2πpT/4500
= 0.837T
Break Sp. Fuel Consumption = 0.1*60/0.837T*5
0.1910 = 0.1/0.837T*5
T=7.5 kg-m.

5. In which of the following condition the engine is known as over-square engine?
a) d < L
b) d > L
c) d=0
d) L=0

Answer: b
Explanation: L/d, known as stroke to bore ratio, is an important parameter in classifying the size of the engine. If d < L, it is called under-square engine. If d = L, it is called square engine. If d>L, it is called over-square engine.

6. Find the weight of air for complete combustion of 10 litres of petrol assuming air contains 22.7% oxygen.
a) 106.10 kg
b) 120kg
c) 113.67 kg
d) 115.79 kg

Answer: c
Explanation: 2C₆H₁₄+19O₂ – – 12CO₂+12H₂O
Density of petrol = 0.77 g/cc
Mass = 10*1000*0.73
7300 g petrol = 19*32*7300/2*86
= 25.80 kg
Amount of air required = 25.80*100/22.7
= 113.67 kg.

7. The pipe which connects the intake system to the inlet valve of the engine and through which air or air-fuel mixture is drawn into the cylinder is known as _______
a) Spark Plug
b) Connecting Rod
c) Camshaft
d) Inlet Manifold

Answer: d
Explanation: Spark plug is a component to initiate the combustion process. Connecting rod connects the piston and the crankshaft and transmits the gas forces from piston to the crankshaft. Camshaft and its associated parts control the opening and closing valves.

8. Who invented two-stroke engine in 1878?
a) Dugald Clark
b) Nikola Tesla
c) Carl Sagan
d) William Henry Bragg

Answer: a
Explanation: Nikola Tesla is best known for his contributions in the design of modern alternating current. Carl Sagan made crucial contributions in popularizing astronomy. Bragg invented the X-ray spectrometer.

9. The mechanical efficiency of a single cylinder four-stroke engine is 80%. The frictional power is estimated to be 25. Calculate the indicated and brake power developed by the engine.
a) 106 kW;120 kW
b) 125 kW;100 kW
c) 120 kW;106 kW
d) 100 kW;125 kW

Answer: b
Explanation: brake power/indicated power = 0.8
Indicated power-brake power = 25
Indicated power-0.8*indicated power
Indicated power = 125 kW
Brake power=100 Kw.

10. If L is the stroke and N is the rpm, mean piston speed of two stroke engine is _______
a) LN
b) LN/2
c) 2LN
d) 2LN/3

Answer: c
Explanation: The mean piston speed is the average speed of the piston in a reciprocating engine. It is a function of stroke and RPM. There is a factor of 2 in the equation to consider one stroke to occur in ½ of a crank revolution.