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Multiple choice question for engineering

Set 1

1. The actual efficiency of a good engine is about _____________ of the estimated air fuel cycle efficiency.
a) 100%
b) 85%
c) 50%
d) 25

View Answer

Answer: b

2. The ratio of the actual efficiency and the and the fuel air cycle efficiency for C.I. engines is about
a) 0.2-0.3
b) 0.5-0.6
c) 1.0
d) 0.6-0.8

View Answer

Answer: d

3. Fuel air efficiency is less than air standard efficiency by an amount equal to
a) pumping loss
b) friction loss
c) loss due to specific heat and chemical equilibrium
d) exhaust blow down loss

View Answer

Answer: c

4. Fuel air ratio affects maximum power output of the engine due to
a) higher specific heats
b) chemical equilibrium losses
c) all of the mentioned
d) none of the mentioned

View Answer

Answer: c

5. As compared to air cycle, in actual working, the effect of variation in specific heats is to
a) increase maximum pressure and maximum temperature
b) reduce maximum pressure and maximum temperature
c) increase maximum pressure and decrease maximum temperature
d) none of the mentioned

View Answer

Answer: b

6. The ratio of actual cycle efficiency to that of the ideal cycle efficiency is called
a) effectiveness
b) work ratio
c) efficiency ratio
d) net efficiency

View Answer

Answer: c [Reason:] Efficiency ratio is the ratio of actual cycle efficiency to that of the ideal cycle efficiency.

7. The ignition of charge by some hot surface in the engine cylinder before operation of spark plug is known as
a) auto ignition
b) pre-ignition
c) detonation
d) none of the mentioned

View Answer

Answer: b [Reason:] Pre-ignition is defined as the ignition of charge by some hot surface in the engine cylinder before operation of spark plug.

8. The break mean effective pressure of an I.C. engine with increase in speed will
a) increase
b) decrease
c) remain same
d) none of the mentioned

View Answer

Answer: c

Set 2

1. For same compression ratio and for same heat added
a) Otto cycle is more efficient than Diesel Cycle
b) Diesel cycle is more efficient than Otto Cycle
c) Efficiency depends on other factors
d) None of the mentioned

View Answer

Answer: a

2. The efficiency of Carnot cycle is maximum for
a) gas engine
b) petrol engine
c) steam engine
d) reversible engine

View Answer

Answer: d

3. For the same compression ratio, the efficiency of dual combustion cycle is
a) greater than otto cycle
b) less than diesel cycle
c) less than otto cycle and greater than diesel cycle
d) greater than both otto and diesel cycle

View Answer

Answer: c

4. If both Stirling and Carnot cycles operate within the same temperature limits, then efficiency of Stirling cycle as compared to Carnot cycle is
a) more
b) less
c) equal
d) none of the mentioned

View Answer

Answer: c

5. Choose the correct statement from the following
a) Diesel cycle is more efficient than Otto cycle for a given compression ratio.
b) Otto cycle is more efficient than Diesel cycle for a given compression ratio.
c) For a given compression ratio, both Otto and Diesel cycles have same efficiency.
d) None of the mentioned

View Answer

Answer: b [Reason:] Otto cycle is more efficient than Diesel cycle for a given compression ratio.

6. For constant maximum pressure and heat input, the air standard efficiency of gas power cycle is in the order.
a) Diesel cycle, Dual cycle, Otto cycle
b) Otto cycle,Diesel cycle, Dual cycle
c) Dual cycle,Otto cycle, Diesel cycle
d) Diesel cycle,Otto cycle, Dual cycle

View Answer

Answer: a

7. Otto cycle efficiency is higher than Diesel cycle efficiency for the same compression ratio and heat input because, in Otto cycle
a) combustion is at constant volume
b) expansion and compression are isentropic
c) maximum temperature is higher
d) heat rejection is lower

View Answer

Answer: d

8. The thermal efficiency of a diesel engine is about
a) 15%
b) 30%
c) 50%
d) 70%

View Answer

Answer: d

Set 3

1. On city roads one may be able to operate the vehicle between ________________ of the throttle only.
a) 30 to 70%
b) 40 to 80%
c) 25 to 60%
d) 25 to 50%

View Answer

Answer: c [Reason:] Generally, on city roads one may be able to operate the vehicle between 25 to 60% of the throttle only.

2. The principle of compensating jet device is to make the mixture
a) leaner
b) equal
c) richer
d) none of the mentioned

View Answer

Answer: a [Reason:] The principle of compensating jet device is to make the mixture leaner as the throttle opens progressively.

3. The compensating well is supplied with fuel from the main float chamber through a
a) nozzle
b) restricting orifice
c) injector
d) none of the mentioned

View Answer

Answer: b

4. The main metering jet is kept at a level of about _______________ below the fuel level in the float chamber.
a) 25 mm
b) 30 mm
c) 35 mm
d) 40 mm

View Answer

Answer: a

5. Back suction control mechanism, is employed in
a) small carburetors
b) medium carburetors
c) large carburetors
d) none of the mentioned

View Answer

Answer: c [Reason:] Back suction control mechanism, is employed only in large carburetors.

6. Auxiliary ports are used for aircraft carburetors to compensate for the _____________ in density of air at high altitudes.
a) increase
b) stable
c) loss
d) none of the mentioned

View Answer

Answer: c [Reason:] For practical purposes, the auxiliary ports are used for aircraft carburetors to compensate for the loss in density of air at high altitudes.

7. In back suction control mechanism, if the valve is closed, the float chamber pressure will ____________ the pressure at the venturi throat.
a) equalize with
b) increase
c) decrease
d) none of the mentioned

View Answer

Answer: a [Reason:] Generally, in back suction control mechanism, if the valve is closed, the float chamber pressure will equalize with the pressure at the venturi throat and no fuel can flow.

8. Which of the following are compensating devices?
a) air-bleed jet
b) compensating jet
c) emulsion tube
d) all of the mentioned

View Answer

Answer: d [Reason:] The compensating devices are air-bleed jet, compensating jet, emulsion tube, back suction control mechanism, auxiliary air valve and auxiliary air port.

9. Which of the following are compensating devices?
a) back suction control mechanism
b) auxiliary air valve
c) auxiliary air port
d) all of the mentioned

View Answer

Answer: d [Reason:] Same as above.

Set 4

1. Diesel cycle is also known as
a) constant volume cycle
b) constant pressure cycle
c) constant temperature cycle
d) none of the mentioned

View Answer

Answer:b [Reason:] Diesel cycle is also known as constant pressure cycle as pressure is constant in this cycle.

2. A diesel engine has compression ratio from
a) 6 to 10
b) 10 to 15
c) 16 to 20
d) 25 to 40

View Answer

Answer: c

3. In Diesel cycle, heat addition takes place at
a) constant temperature
b) constant pressure
c) constant volume
d) none of the mentioned

View Answer

Answer: b

4. The combustion in compression ignition engine is
a) homogeneous
b) heterogeneous
c) laminar
d) none of the mentioned

View Answer

Answer: b

5. In a diesel engine, the fuel is ignited by
a) spark
b) injected fuel
c) heat resulting from compressing air that is supplied for combustion
d) combustion chamber

View Answer

Answer: c

6. The thermal efficiency of a diesel cycle having fixed compression ratio, with increase in cut-off ratio will
a) increase
b) decrease
c) be independent
d) none of the mentioned

View Answer

Answer: b

7. The pressure at the end of compression, in diesel engines, is approximately
a) 10 bar
b) 20 bar
c) 25 bar
d) 35 bar

View Answer

Answer: d

8. The combustion in spark ignition engine is
a) homogeneous
b) heterogeneous
c) laminar
d) none of the mentioned

View Answer

Answer: a [Reason:] The combustion in spark ignition engine is homogeneous while the combustion in compression ignition engine is heterogeneous.

9. If the temperature of intake air in I.C. engine is lowered, then its efficiency will
a) increase
b) decrease
c) remain same
d) increase up to certain limit and then decrease

View Answer

Answer: a

10. The fuel in diesel engine is normally injected at pressure of
a) 5-10 kg/cm2
b) 20-25 kg/cm2
c) 60-80 kg/cm2
d) 90-130 kg/cm2

View Answer

Answer: d

Set 5

1. Dissociation is the disintegration of burnt gases at __________ temperatures.
a) low
b) high
c) constant
d) none of the mentioned

View Answer

Answer: b

2. In lean mixtures no dissociation takes place at_____________ temperatures.
a) low
b) high
c) constant
d) none of the mentioned

View Answer

Answer: a

3. In rich mixtures dissociation is prevented by the available
a) CO
b) CO2
c) O2
d) CO and O2

View Answer

Answer: d

4. Power output is maximum at stoichiometric ratio where there is
a) dissociation
b) no dissociation
c) rich mixture
d) none of the mentioned

View Answer

Answer: b

5. Maximum dissociation is for
a) lean mixture
b) rich mixture
c) stoichiometric
d) none of the mentioned

View Answer

Answer: c [Reason:] Maximum dissociation is for stoichiometric mixtures while in lean mixtures, generally no dissociation takes place.

6. With dissociation, peak temperature is obtained
a) at the stoichiometric ratio
b) when the mixture is slightly lean
c) when the mixture is slightly rich
d) none of the mentioned

View Answer

Answer: c

7. With dissociation the exhaust gas pressure
a) decreases
b) increases
c) no effect
d) increases upto certain air fuel ratio and then decreases

View Answer

Answer: a

8. For a given compression ratio, as the mixture is made progressively rich from lean the mean effective pressure
a) increases
b) decreases
c) initially increases then decreases
d) remains more or less same

View Answer

Answer: c

9. When the mixture is lean
a) efficiency is less
b) power output is less
c) maximum temperature and pressure are higher
d) all of the mentioned

View Answer

Answer: b [Reason:] Power output is less when the mixture is lean.

10. For a compressor process with variable specific heat the peak temperature and pressure are
a) lower
b) higher
c) no effect
d) none of the mentioned

View Answer

Answer: a

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