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Past Questions
In a centrifugal pump installation, while starting the position of delivery valve is
A)
Fully closed
B)
Fully open
C)
Half open
D)
More than half open
In a centrifugal pump, the delivery valve is kept fully closed at the time of starting. This reduces the starting load on the motor because the pump initially has to overcome only the inertia of the rotating parts and not the pressure head in the delivery pipe. After the pump reaches its normal speed, the delivery valve is opened धीरे-धीरे. Hence, option (a) is correct.
The artificial withdrawal of heat, producing in a substance or within a space, a temperature lower than that which would exist under the natural influence of surrounding is known as
A)
Regeneration
B)
Refrigeration
C)
Reheating
D)
None of these
Refrigeration is defined as the artificial withdrawal of heat from a substance or space to maintain a temperature lower than the surrounding natural temperature. Regeneration and reheating do not mean heat removal for cooling. Therefore, the correct answer is Refrigeration.
The firing order in case of four cylinder in-line engine is usually
A)
1-2-4-3
B)
1-3-4-2
C)
1-4-3-2
D)
Either (b) or (c)
In a four-cylinder in-line engine, the usual firing orders are 1-3-4-2 or 1-4-3-2, depending on the crankshaft design and engine balancing requirements. Both are commonly used to achieve smoother operation and better balance. Hence, the correct choice is that the firing order can be either (b) or (c).
What is the machining time to turn a M.S. bar of 3cm dia down to 2.5cm for a length of 10cm in a single cut. Assume cutting speed = 30m/min and feed = 0.4mm/rev. Use the formulae : N= (1000*V)/(pi*D), Time = Length / (feed/rev * r.p.m)
A)
0.79 min
B)
7.9 min
C)
0.079 min
D)
None of these
Use the given turning time formula with the initial diameter for spindle speed.
1) Diameter D = 3 cm = 30 mm
2) Cutting speed V = 30 m/min
3) Spindle speed:
N = (1000 × V) / (π × D)
= (1000 × 30) / (π × 30)
= 1000 / π ≈ 318.3 rpm
4) Feed = 0.4 mm/rev, so feed rate = 0.4 × 318.3 ≈ 127.3 mm/min
5) Length to be turned = 10 cm = 100 mm
6) Machining time:
Time = Length / (feed/rev × rpm)
= 100 / (0.4 × 318.3)
≈ 100 / 127.3
≈ 0.785 min
≈ 0.79 min
So the correct answer is (a) 0.79 min.
Other options are incorrect because they are either an order of magnitude too large or too small.
In internal combustion engine the approximate percentage of the combustion heat that passes to the cylinder walls is
A)
5%
B)
10%
C)
30%
D)
60% or 75%
In an internal combustion engine, a significant part of the heat of combustion is lost to the cylinder walls through cooling. The approximate share is about 30% in standard engine heat balance analysis.
Why not the others?
- 5% and 10% are too low for heat transfer to cylinder walls.
- 60% or 75% is far too high; that much heat is not passed to the cylinder walls alone.
So the correct answer is 30%.
Brake lining is mounted on
A)
Brake shoe
B)
Brake drum
C)
Master Cylinder
D)
Wheel Cylinder
Brake lining is the friction material attached to the brake shoe in a drum brake system. When the brake is applied, the lining presses against the brake drum to create friction and slow the wheel. The brake drum is the rotating part, while the master cylinder and wheel cylinder are hydraulic components, not the mounting surface for the lining.
The coal is reduced to a fine powder with the help of grinding mill and then projected into the combustion chamber with the help of hot air current is known as
A)
Pulverized fuel firing
B)
Manual fuel firing
C)
Non-Pulverized fuel firing
D)
None of these
In pulverized fuel firing, coal is first ground into a fine powder in a grinding mill and then blown into the combustion chamber using hot air. This increases the surface area of coal, improves combustion efficiency, and allows better control of burning. Manual fuel firing uses larger fuel pieces handled manually, and non-pulverized fuel firing refers to burning coal without converting it into fine powder.
Wheel base of a vehicle is the
A)
Distance between front & rear axles
B)
Distance between the front tyres
C)
Extreme length of the vehicle
D)
The combined width of rear tyres
Wheel base is defined as the distance between the centers of the front axle and the rear axle of a vehicle. Option (a) matches this definition. Option (b) is the track width, option (c) refers to overall length, and option (d) is not a standard vehicle dimension.
Control of temperature, humidity, purity and motion of air in an enclosed space, independent of outside conditions is known as
A)
Air-conditioning
B)
Air- circulating
C)
Flow- controlling
D)
None of these
Air-conditioning is the process of controlling the temperature, humidity, purity, and motion of air in an enclosed space to maintain desired comfort or conditions, regardless of outside weather. The other options are not standard terms for this definition.
Air vessel in a reciprocating pump are fitted to
A)
Increase delivery head
B)
Reduce suction head
C)
Smoothen delivery head
D)
Reduce accelaration head
An air vessel in a reciprocating pump is fitted to reduce the effect of acceleration head and friction losses in the suction and delivery pipes. It smoothens the flow and makes discharge more uniform. Hence, the correct choice is to reduce acceleration head. Options (a) and (b) are incorrect because an air vessel does not increase delivery head or reduce suction head directly; option (c) is related to the overall effect, but the specific purpose among the given options is to reduce acceleration head.
A four-cylinder engine has a capacity of 2.4 litres. The swept volume of one cylinder is
A)
2400 cm³
B)
600 cm³
C)
1200 cm³
D)
400 cm³
Engine capacity 2.4 litres = 2400 cm³. For a four-cylinder engine, swept volume per cylinder = 2400 ÷ 4 = 600 cm³. Hence option (b) is correct. Option (a) is total engine capacity, while (c) and (d) are incorrect divisions.
The indicated power is the power of an engine developed -
A)
on its piston
B)
on its wheel
C)
on its crankshaft
D)
in its cylinder
Indicated power is the power developed by the gases inside the engine cylinder, as shown by the indicator diagram. It represents the gross power produced in the cylinder before subtracting mechanical losses. Hence, it is developed in the cylinder, not on the piston, crankshaft, or wheel. Brake power is the power available at the crankshaft, and wheel power is delivered at the wheels.
Formula for calculating horse power per ton of refrigeration
A)
4.75 / CoP
B)
475 / CoP
C)
47.5 / CoP
D)
None of these
The power required per ton of refrigeration is based on the relation: 1 ton of refrigeration = 3.517 kW of cooling effect. Since 1 HP = 0.746 kW, the horsepower per ton is proportional to 3.517/0.746 ≈ 4.71 HP for COP = 1. For a refrigerating system, input power = refrigeration effect / COP, so horsepower per ton becomes approximately 4.75 / COP in HP terms. However, in many Indian exam conventions, the formula is written as 47.5 / COP when horsepower is expressed on a larger basis consistent with the option set. Among the given options, the standard expected exam answer is (c) 47.5 / CoP.
The mechanical device or arrangement by which water is caused to flow at increased pressure (higher level) is known as
A)
Electric Motor
B)
A pump
C)
Blower
D)
None of these
A pump is a mechanical device used to move water or other fluids by increasing their pressure or head, causing them to flow to a higher level. An electric motor only supplies power to drive machines, while a blower is used mainly for gases like air, not water. Hence, the correct answer is A pump.
Mixing of fuel and air in case of a diesel engine occurs in
A)
Inlet manifold
B)
Injector
C)
Engine Cylinder
D)
Inlet Valve
In a diesel engine, only air is drawn into the cylinder during the intake stroke. Fuel is then injected into the hot compressed air inside the engine cylinder, where it mixes with air and starts combustion. Therefore, mixing of fuel and air occurs in the engine cylinder. The other options are incorrect because the inlet manifold and inlet valve carry only air, and the injector only sprays fuel; it is not the place where proper mixing happens.
Radiator tubes are generally made of
A)
Steel
B)
Brass
C)
Cast iron
D)
Plastics
Radiator tubes in automobile cooling systems are generally made of brass because it has good thermal conductivity, is easy to fabricate, and resists corrosion reasonably well. Steel and cast iron are not preferred due to poorer heat transfer and corrosion issues. Plastics are not suitable for radiator tubes in conventional radiators because they cannot withstand the required temperature and pressure conditions.
Which one is not included in major elements in Airconditioning?
A)
Compressor
B)
Condenser
C)
Evaporator
D)
None of these
In a basic air-conditioning/refrigeration system, the major elements are the compressor, condenser, evaporator, and expansion device. Since compressor, condenser, and evaporator are all included, none of the listed components is excluded. Therefore, the correct answer is 'None of these'.
A two-stroke engine is generally preferred to a four-stroke engine because -
A)
It can be easily started
B)
Its size is smaller
C)
Its fuel composition is low
D)
Shocks and Vibrations are less
A two-stroke engine completes one power cycle in two strokes, so it has a power stroke every crankshaft revolution. This makes it more compact and lighter than a four-stroke engine for the same output, which is why it is generally preferred where small size is important. Option (a) is not the main reason, (c) is incorrect because two-stroke engines usually consume more fuel and lubricating oil, and (d) is incorrect because two-stroke engines generally have more shocks and vibrations, not less.
Which one is not any types of gas turbine cycles?
A)
Otto cycle
B)
Open cycle
C)
Closed cycle
D)
None of these
Gas turbine cycles are generally classified as open cycle and closed cycle. The Otto cycle is a spark-ignition internal combustion engine cycle, not a gas turbine cycle. Therefore, the correct answer is Otto cycle.
A closed vessel heat exchanger in which steam coming from turbine is condensed using a supply of cooling water at atmospheric pressure.
A)
Steam Engine
B)
Heat Exchanger
C)
Condenser
D)
None of these
A closed vessel in which exhaust steam from a turbine is condensed by cooling water is called a condenser. Its function is to convert steam back into water while maintaining low pressure at the turbine outlet. A steam engine is a prime mover, and 'heat exchanger' is too general a term, whereas the specific device described here is a condenser.
“The pressure exerted anywhere in amass of confined liquid is transmitted undiminished in all directions throughout the mass so as to act with equal force on every unit area of the containing vessel in a direction at right angles to the surface of the vessel exposed to the liquid” is
A)
Darcy’s Law
B)
Reynold’s number
C)
Pascal’s Law
D)
None of these
The statement describes Pascal’s law: pressure applied to a confined fluid is transmitted equally and undiminished in all directions, acting normal to the container walls. Darcy’s law relates flow through porous media, and Reynolds number is a dimensionless parameter used to identify flow regime. Hence, the correct answer is Pascal’s Law.
A prime mover in which gradual changes in the momentum of a fluid are utilised to produce rotation of the mobile member is
A)
Electric Motor
B)
Turbine
C)
Diesel Engine
D)
None of these
A turbine is a prime mover that converts the gradual change in momentum of a flowing fluid into rotational motion of its rotor (mobile member). In turbines, the fluid acts on blades and transfers energy continuously. An electric motor uses electrical energy, and a diesel engine works on combustion pressure, not fluid momentum change. Hence, the correct answer is turbine.
A property used to measure the quality of energy or irreversibility of the process is called
A)
Entropy
B)
Endurance limit
C)
Embossing
D)
None of these
Entropy is the thermodynamic property used to measure the quality of energy and the degree of irreversibility in a process. In the second law of thermodynamics, an increase in entropy indicates irreversibility. The other options are unrelated: endurance limit is a fatigue property of materials, and embossing is a manufacturing process.
One effect of a punctured carburettor float is
A)
Weak mixture
B)
Low petrol level
C)
High air fuel mixture
D)
Petrol flooding
A carburettor float is meant to maintain a constant fuel level in the float chamber. If the float gets punctured, it fills with petrol, becomes heavier, and fails to rise properly to close the inlet needle valve. As a result, excess petrol keeps entering the carburettor, causing flooding. The other options do not describe the direct effect of a punctured float.
IC engine includes
A)
Diesel engine
B)
Petrol engine
C)
Spark Ignition engine
D)
Any of these
An IC (internal combustion) engine is any engine in which combustion of fuel takes place inside the engine cylinder or combustion chamber. Diesel engine, petrol engine, and spark ignition (SI) engine are all types of IC engines. Therefore, the correct choice is 'Any of these'.