← Junior Engineer
Past Questions
If petrol is used in a diesel engine, then -
A)
Higher knocking will occur
B)
Efficiency will be low
C)
Low power will be produced
D)
Black smoke will be produced
Petrol ignition delay is large, causing accumulation and severe knock in diesel engine.
The amount of heat generated per kg of fuel is known as -
A)
Calorific value
B)
Heat energy
C)
Lower calorific value
D)
Higher calorific value
Calorific value is heat released per unit mass of fuel on complete combustion.
To avoid cavitation in centrifugal pumps -
A)
Suction pressure should be low
B)
Delivery pressure should be low
C)
Suction pressure should be high
D)
Delivery pressure should be high
Cavitation is avoided by increasing NPSHa; keeping suction pressure high prevents vapour formation.
Cycle used in thermal power plants is -
A)
Carnot
B)
Reversed carnot
C)
Rankine
D)
Brayton
Thermal power plants use Rankine cycle for steam power.
The main function of nozzle is to
A)
Varying temperatures
B)
Pressure variations
C)
Load variations
D)
Heat variations
In turbines nozzle governing controls flow to meet load variations by opening/closing nozzles.
The domestic refrigerator uses following type of compressor -
A)
Centrifugal
B)
Axial
C)
Miniature sealed unit
D)
Piston type reciprocating
Domestic refrigerator uses hermetically sealed miniature sealed unit reciprocating compressor.
Which of the following is a classification of automobiles based on Load?
A)
Heavy transport vehicle (HTV)
B)
Sedan Hatchback car
C)
Four wheeler vehicle
D)
Front-wheel drive
Heavy transport vehicle (HTV) is a classification based on load-carrying capacity. Vehicles are commonly classified by load into light, medium, and heavy transport vehicles. The other options are not load-based classifications: Front-wheel drive is a drivetrain type, Four wheeler vehicle is a classification by number of wheels, and Sedan Hatchback car is a body/style classification.
Which of the following is necessary for the description of an automobile?
A)
Make
B)
Model
C)
Capacity
D)
Allofabove
Complete automobile description needs make, model and capacity. All needed.
As aresult of detonation in an I.C. engine, following parameter attains very high value -
A)
Rate ofrise of pressure
B)
Rate ofrise of temperature
C)
Peak temperature
D)
Peak pressure
Detonation causes extremely rapid pressure rise, high dP/dt leading to knock.
Hydraulic ram is a pump which works -
A)
On the principle of centrifugal action
B)
On the principle of reciprocating action
C)
Onthe principle of water hammer
D)
On the principle of reaction
Hydraulic ram uses water hammer effect to lift part of water to higher elevation.
If the intake air temperature of I.C. engine increases, its efficiency will -
A)
Increase
B)
Decrease
C)
Remain same
D)
Unpredictable
Higher intake temperature reduces air density and volumetric efficiency, lowering thermal efficiency.
The comfort conditions in air conditioning system are defined by -
A)
22°C dry bulb temperature (DBT) and 60% relative humidity (RH)
B)
25°C DBT and 100% RH
C)
20°C DBT and 75% RH
D)
25°C DBT and 40% RH
Commonly quoted comfort is ~22°C DBT and 60% RH, other standards 25°C/50% RH.
A Francis turbine is used when the available head of water is -
A)
25mto250m
B)
0to 25m
C)
250mto300m
D)
Above 300m
A Francis turbine is a mixed-flow reaction turbine used for medium heads, typically about 25 m to 250 m. Therefore, the correct option is (a) 25 m to 250 m. Option (b) 0 to 25 m corresponds to low-head applications where Kaplan/propeller turbines are preferred. Options (c) 250 m to 300 m and (d) above 300 m are high-head ranges, for which Pelton turbines are generally used.
A spark plug gap is generally kept from -
A)
0to0.3mm
B)
0.3 to 0.7 mm
C)
0.5 to 0.8 mm
D)
0.6to 1.0mm
Typical spark plug electrode gap is 0.6-1.0 mm to ensure reliable spark.
Formation of frost on evaporator in refrigerator -
A)
Resultsinloss of heat due to poor heat transfer
B)
Increases heat transfer rate
C)
Jsimmaterial
D)
Decreases compressor power
Frost is insulating layer, reduces heat transfer and increases power consumption.
As per common design practice, the three types of hydraulic turbines, in descending order of flow rate, are -
A)
Pelton, Francis, Kaplan
B)
Pelton, Kaplan, Francis
C)
Francis, Kaplan, Pelton
D)
Kaplan, Francis, Pelton
The correct descending order of flow rate is **Kaplan > Francis > Pelton**, so the correct option is **d**.
- **Kaplan turbine** is an axial-flow reaction turbine and handles the **highest discharge/flow rate**.
- **Francis turbine** is a mixed-flow reaction turbine and operates at a **moderate flow rate**.
- **Pelton turbine** is an impulse turbine and works with **low discharge** but high head, so it has the **lowest flow rate** among the three.
Why the other options are wrong:
- **a (Pelton, Francis, Kaplan)**: reverse of the correct order.
- **b (Pelton, Kaplan, Francis)**: Pelton is incorrectly placed first; it has the lowest flow rate.
- **c (Francis, Kaplan, Pelton)**: Kaplan should come before Francis, not after it.
Hence, the correct answer is **d**.
Which of the following provides passages for the flow of cooling water?
A)
Crankcase
B)
Piston
C)
Cylinder block
D)
Cylinder head
The correct option is **c) Cylinder block**. In a water-cooled engine, the **cylinder block** contains the water jackets/passages through which cooling water circulates around the cylinders to absorb heat and prevent overheating.
Why the others are incorrect:
- **b) Piston**: The piston moves inside the cylinder and does not provide cooling-water passages.
- **d) Cylinder head**: The cylinder head may also contain water passages, but the standard main component specifically associated with passages for cooling water around the cylinders is the cylinder block.
- **a) Crankcase**: The crankcase houses the crankshaft and lubricating oil, not cooling-water passages.
A perpetual motion machine is -
A)
A thermodynamic machine
B)
anon-thermodynamic machine
C)
ahypothetical machine
D)
ahypothetical machine whose operation would violate the laws of thermodynamics
A perpetual motion machine is a hypothetical machine that would operate indefinitely and produce work without any energy input. Such a device would violate the laws of thermodynamics, especially the first and second laws, so option d is correct. Option c is too vague because not every hypothetical machine is a perpetual motion machine. Option a is incorrect because a perpetual motion machine is not a normal thermodynamic machine. Option b is incorrect because the term is not defined as a non-thermodynamic machine; it is specifically a machine that would contradict thermodynamic laws.
The minimum temperature to which water can be cooled in a cooling tower is -
A)
Dew point temperature of air
B)
Wet bulb temperature of air
C)
Dry bulb temperature of air
D)
Ambient air temperature
Theoretical minimum water temperature achievable is wet-bulb temperature of entering air.
The negative plates of a lead acid battery has -
A)
Lead peroxide (PbO2)
B)
Spongy lead (Pb)
C)
Lead sulphate (PbSO4)
D)
Sulphuric acid (H2SO4)
Lead-acid negative plates are spongy lead Pb, positive is PbO2.
When a gas flows through a very long pipe of uniform cross section, the flow is approximately -
A)
Isentropic
B)
Isobaric
C)
Isothermal
D)
Adiabatic
In very long pipe heat transfer makes gas temperature approach surroundings, approximately isothermal.
Francis, Kaplan and Propeller turbines fall under the category of -
A)
Impulse turbines
B)
Reaction turbines
C)
Axial flow turbines
D)
Mixed flow turbines
Francis, Kaplan and propeller are all reaction turbines converting pressure energy to kinetic.
Which of the following has the highest calorific value?
A)
Anthracite coal
B)
Bituminous coal
C)
Peat
D)
Lignite
Anthracite coal has the highest calorific value among the given fuels because it is the highest rank of coal, with the greatest carbon content and the least moisture and volatile matter. As coal rank increases from peat to lignite to bituminous to anthracite, calorific value generally increases. Peat has the lowest calorific value because it is the least carbonized and contains the most moisture. Lignite has a higher calorific value than peat but lower than bituminous coal. Bituminous coal has a high calorific value, but anthracite is still higher due to its higher fixed carbon content and lower impurities.
Pelton wheel are used for minimum of following heads-
A)
20 meter
B)
100 meter
C)
125 meter
D)
180 meter and above
Pelton wheels are impulse turbines for high heads, economical generally above 150-180 m.
Which of the following items is not a path function?
A)
Heat
B)
Work
C)
Kinetic energy
D)
Thermal conductivity
Heat, work and kinetic energy depend on path; thermal conductivity is a material property (point function).