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Past Questions
Petrol engine works on
A)
Diesel cycle
B)
Dual cycle
C)
Otto cycle
D)
None of these
A petrol engine is a spark-ignition engine, and its ideal thermodynamic cycle is the Otto cycle. The Otto cycle consists of two constant-volume processes and is the standard cycle for petrol engines. Diesel engines work on the Diesel cycle, and some engines may approximate the dual cycle, so those options are incorrect here.
“It is impossible to construct an engine to work in a cyclic process whose sole effect is to convert all the heat supplied to it into an equivalent amount of work” is
A)
2nd Law of Thermodynamics : Kelvin - Planck Statement
B)
1st Law of Thermodynamics
C)
2nd Law of Thermodynamics : Clausius Statement
D)
None of these
The statement given is the Kelvin-Planck statement of the Second Law of Thermodynamics. It says that no heat engine operating in a cycle can convert all the heat absorbed from a single reservoir entirely into work; some heat must be rejected. The First Law only deals with conservation of energy and does not forbid 100% conversion of heat to work. The Clausius statement is different: it says heat cannot flow from a colder body to a hotter body without external work.
A prime mover in which gradual changes in the momentum of a fluid are utilised to produce rotation of a mobile member is
A)
Electric Motor
B)
Turbine
C)
Diesel Engine
D)
None of these
A turbine is a fluid machine in which the gradual change in momentum of a moving fluid is used to produce rotation of a rotor or mobile member. The fluid exerts force on the blades, causing shaft rotation. An electric motor and a diesel engine are not fluid machines of this type, so they are incorrect.
Air vessel in a reciprocating pump are fitted to
A)
Increase delivery head
B)
Reduce suction head
C)
Smoothen delivery head
D)
Reduce acceleration head
An air vessel in a reciprocating pump is used to reduce the fluctuations in flow and pressure caused by the reciprocating motion of the piston. By storing and releasing water during the cycle, it helps reduce the acceleration head and also minimizes friction losses. Hence, the correct option is (d). Options (a) and (b) are not the purpose of an air vessel, and (c) is a broader effect, but the standard specific answer is reduction of acceleration head.
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 portion of the fuel’s heat is lost to the cooling water and cylinder walls. The approximate heat transfer to the cylinder walls is about 30%. Hence option (c) is correct. The other options are not consistent with standard IC engine heat-balance data: 5% and 10% are too low, while 60% or 75% is too high for heat passing directly to the cylinder walls.
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 front axle and the rear axle of a vehicle. Therefore, option (a) is correct. Option (b) refers to front track width, option (c) is overall length, and option (d) is not the definition of wheel base.
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 used in power plants/thermal systems to condense exhaust steam from a turbine using cooling water is called a condenser. It rejects heat from the steam to the cooling water and converts the steam back into liquid water. A steam engine is a prime mover, and 'heat exchanger' is a broader term, but the specific device described here is a condenser.
Which one is not the type of gas turbine?
A)
Constant volume type
B)
Constant pressure type
C)
Compression ignition Engine type
D)
None of these
Gas turbines are generally classified by the combustion process into constant pressure type and constant volume type. A compression ignition engine is a type of internal combustion reciprocating engine (diesel engine), not a gas turbine. Therefore, option (c) is not a type of gas turbine. Option (a) and (b) are both valid gas turbine types, so (d) cannot be 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
The statement defines the process of removing heat artificially to maintain a temperature below the surroundings. This is called refrigeration. Regeneration means recovering energy or material for reuse, and reheating means increasing temperature after cooling. Therefore, the correct answer is Refrigeration.
Formula for calculating horse power per ton of refrigeration
A)
475 / COP
B)
475 * COP
C)
COP
D)
None of these
For a refrigeration system, 1 ton of refrigeration = 3.517 kW of cooling. The compressor power required depends on the COP:
Power (kW) = Refrigeration effect / COP.
Converting this to horsepower and using the standard approximation used in HVAC problems gives horse power per ton of refrigeration as 475 / COP. Therefore, option (a) is correct.
Option (b) is incorrect because horsepower increases with lower COP, not with higher COP. Option (c) is just COP itself, which is not a power formula. Option (d) is incorrect because the correct formula is listed in option (a).
A process, which can be reversed, cannot lead to the initial state of the system and the surroundings without external inputs, is
A)
Irreversible process
B)
Reversible process
C)
Constant process
D)
None of these
A reversible process can return both the system and surroundings exactly to their initial states by an infinitesimal change, without leaving any net change. If a process cannot restore the initial state of the system and surroundings without external input, it is an irreversible process. Hence, option (a) is correct. Options (b) is opposite in meaning, and (c) is not a standard thermodynamics term for this definition.
Which one is not included in one of advantages of gas turbine?
A)
Braking is not effective due to very high speed
B)
Gas turbine is smooth in operation and continuous in performance
C)
It does not have reciprocating parts, hence it is easy to balance. It is free from vibration.
D)
None of these
Gas turbines are known for smooth, continuous operation, absence of reciprocating parts, easy balancing, and very low vibration. These are genuine advantages, so options (b) and (c) are correct advantages. Option (a) is not an advantage of a gas turbine; it is a limitation/undesirable feature related to high speed operation. Therefore, the correct answer is (a).
What is the machining time to turn a MS. 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.
A)
0.79 min
B)
7.9 min
C)
0.079 min
D)
None of these
For turning, machining time = Length of cut / (feed × spindle speed).
Given:
- Initial diameter D = 3 cm = 30 mm
- Cutting speed V = 30 m/min
- Feed f = 0.4 mm/rev
- Length of cut L = 10 cm = 100 mm
Spindle speed:
N = (1000 × V) / (π × D)
= (1000 × 30) / (π × 30)
= 1000 / π
≈ 318.3 rev/min
Machining time:
T = L / (f × N)
= 100 / (0.4 × 318.3)
≈ 100 / 127.32
≈ 0.785 min
≈ 0.79 min
So the correct answer is (a) 0.79 min.
Options (b) and (c) are incorrect because they are too large or too small by about a factor of 10.
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 very fine powder in a grinding mill and then blown into the combustion chamber using hot air. This increases the surface area of coal, so it burns rapidly and efficiently. Manual fuel firing involves feeding solid fuel by hand, while non-pulverized fuel firing uses coal without pulverizing it.
Brake lining is mounted on
A)
Brake shoe
B)
Brake drum
C)
Master Cylinder
D)
Wheel Cylinder
Brake lining is the friction material fixed to the brake shoe in drum brakes. When the brake is applied, the brake shoe with its lining presses against the brake drum to create friction and slow the vehicle. 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 law of conservation of energy, according to which the total energy of an isolated system in all its forms remains constant. For a closed system executing a cycle only through heat and work, the change in internal energy is zero”, known as
A)
Second Law of Thermodynamics
B)
Newton’s First Law of Motion
C)
First Law of Thermodynamics
D)
None of these
The statement describes the law of conservation of energy in thermodynamics. It says that energy cannot be created or destroyed, only converted from one form to another. For a closed system undergoing a cycle, the net change in internal energy is zero, which is exactly the First Law of Thermodynamics. The Second Law deals with entropy and direction of heat transfer, and Newton’s First Law is about motion, so both are incorrect.
A clutch is
A)
A friction device which permits the connection and disconnection of shafts
B)
A device to reduce the speed
C)
A part of machine which supports the body
D)
None of these
A clutch is used to connect and disconnect the driving and driven shafts, usually by frictional contact. This allows smooth transmission of power in vehicles and machines. Option (b) describes a speed reducer/gearbox, and option (c) refers to a support structure, not a clutch.
The stresses on the principal planes will be pure normal (tension or compression) and their values are called
A)
Principal stresses
B)
Safe stresses
C)
Shear stresses
D)
None of these
On the principal planes, shear stress is zero and only normal stress acts (tension or compression). These normal stresses are called principal stresses. Safe stresses are allowable design stresses, and shear stresses act on planes where tangential force exists, so they are not correct.
A process of joining similar metals by application of heat with or without application of pressure and addition of filler material is called
A)
Smithing
B)
Forging
C)
Pattern making
D)
Welding
Joining similar metals by applying heat, with or without pressure and with or without filler material, is the definition of welding. Smithing and forging are metal-shaping processes, while pattern making is used in casting to create patterns for molds.
Power may be transmitted between parallel shafts by means of
A)
Worm gears
B)
Clutches
C)
Roller chains
D)
None of these
Power transmission between parallel shafts is commonly done by belts, chains, or gears arranged for parallel shafts. Among the given options, roller chains are used to transmit power between parallel shafts. Worm gears are used for non-parallel, non-intersecting shafts, and clutches are for engaging/disengaging power transmission, not for shaft-to-shaft transmission between parallel shafts.
The ratio between lateral strain to longitudinal strain produced by a single stress is called
A)
Principal ratio
B)
Poisson’s ratio
C)
Bending ratio
D)
None of these
When a material is subjected to a single axial stress, it undergoes a longitudinal strain in the direction of load and a lateral strain perpendicular to it. The ratio of lateral strain to longitudinal strain is called Poisson’s ratio. The other options are not standard terms for this definition.
The tools which are used for checking the size, shape and relative positions of various parts but not provided with graduated adjustable members are
A)
Gauges
B)
Measuring tape
C)
Laser
D)
None of these
Gauges are inspection tools used to check size, shape, and relative position of parts without giving a direct numerical reading. They generally do not have graduated adjustable members. Measuring tape is a direct measuring instrument with graduations, and laser instruments are used for precise measurement/alignment, not this basic gauging definition. Hence, the correct answer is Gauges.
Stresses which are normal to the plane on which they act are called
A)
Direct stresses
B)
Indirect stresses
C)
Proof stresses
D)
None of these
Stresses that act perpendicular (normal) to the plane on which they act are called direct stresses. They include tensile and compressive stresses. Shear stresses, on the other hand, act tangentially to the plane. Therefore, option (a) is correct.
The process which keeps the actual standard as nearby as possible to the predetermined standards by strict supervision is known as
A)
Budgetary control
B)
Physical control
C)
Production control
D)
None of these
The statement describes a control system that keeps actual performance close to predetermined standards through strict supervision. This is the definition of **physical control**, which deals with controlling actual operations, quantities, quality, and physical outputs.
- **Budgetary control** relates to financial planning and control of costs and expenses.
- **Production control** is broader and deals with regulating production activities, but the phrase about strict supervision and keeping actual standards close to predetermined standards specifically matches **physical control**.
- Therefore, the correct answer is **(b) Physical control**.
A machine in which a metal cutting operation is performed by means of a rotating abrasive wheel that acts as a cutting tool and is used to finish workpiece which must show a high surface quality, accuracy of shape and dimension is
A)
Drilling machine
B)
Grinding machine
C)
Boring machine
D)
None of these
A grinding machine performs metal cutting using a rotating abrasive wheel. It is mainly used for finishing operations where high surface quality, accuracy of shape, and dimensional precision are required. Drilling machines are used to make holes, and boring machines enlarge existing holes, so they do not match the description.