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Past Questions — 2015
A Pelton wheel is
A)
Inward flow impulse turbine
B)
Mixed flow reaction turbine
C)
Outward flow reaction turbine
D)
Axial flow impulse turbine
A Pelton wheel is an impulse turbine in which the water jet strikes the buckets tangentially. Among the given options, the only impulse turbine choice is (d). The other options are reaction turbines: inward flow, mixed flow, and outward flow reaction turbines are not Pelton wheels. Note: the standard classification of Pelton wheel is actually a tangential flow impulse turbine; since that exact option is not given, (d) is the closest and intended choice in this question set.
Which part of the engine is directly driven by the starting motor?
A)
Pulley
B)
Flywheel
C)
Crankshaft
D)
Camshaft
The starting motor (starter motor) engages with the ring gear mounted on the flywheel, so it directly drives the flywheel to crank the engine. The flywheel then turns the crankshaft and starts the engine. The crankshaft is driven indirectly through the flywheel, and the camshaft is driven by the crankshaft through gears/chain/belt. A pulley is not the direct part driven by the starter motor.
Embarrassed is to humiliated as frightened is to
A)
reckless
B)
agitated
C)
courageous
D)
terrified
The relationship is one of synonym/near-synonym. "Embarrassed" and "humiliated" both express a similar feeling of shame. Likewise, "frightened" and "terrified" both mean very afraid. The other options do not match this relationship: reckless = careless, agitated = disturbed, courageous = brave.
By supercharging
A)
Power stroke becomes stronger
B)
Loss in exhaust is reduced
C)
Engine can be made to run smoother
D)
Thermal efficiency of the engine can be improved
Supercharging means supplying the engine cylinder with air at a pressure higher than atmospheric pressure. This increases the density of the charge, so more fuel can be burned in each cycle. As a result, the pressure developed during combustion is higher and the power stroke becomes stronger. Option (d) is not generally correct because supercharging mainly increases power output; thermal efficiency does not necessarily improve and may even decrease due to higher losses. Options (b) and (c) are not the direct effect of supercharging.
Otto cycle is generally known as
A)
Diesel engine
B)
Petrol engine
C)
Duel cycle engine
D)
Brayton cycle
The Otto cycle is the ideal thermodynamic cycle for spark-ignition engines, which are commonly petrol engines. It involves heat addition at constant volume and is used to model petrol engine operation. Diesel engines follow the Diesel cycle, dual combustion engines follow the dual cycle, and Brayton cycle is used for gas turbines.
The sequence of processes that eventually returns the working substance to its original state is known as
A)
Event
B)
Zeroth law of thermodynamics
C)
Thermodynamic cycle
D)
Thermodynamic property
A sequence of thermodynamic processes that brings the working substance back to its initial state is called a thermodynamic cycle. In a cycle, the system ends where it started, so the net change in state properties over the complete sequence is zero. The other options are incorrect: an event is not a thermodynamic term, the zeroth law concerns thermal equilibrium and temperature, and a thermodynamic property is a state variable like pressure, temperature, or volume.
Which type of pump is different from other?
A)
Axial flow pump
B)
Plunger pump
C)
Mixed flow pump
D)
Multistage centrifugal pump
Axial flow pump, mixed flow pump, and multistage centrifugal pump are all types of rotodynamic pumps. A plunger pump is a positive displacement pump, so it is different from the others. Hence, the odd one out is Plunger pump.
Power assisted brakes are often provided on
A)
motor cycles
B)
air cooled engine vehicles
C)
road roller
D)
heavy duty vehicles
Power-assisted brakes are used where a large braking force is required with minimum driver effort. This is common in heavy duty vehicles such as trucks and buses. Motor cycles generally use simple mechanical/hydraulic brakes, and road rollers or air-cooled engine vehicles are not the standard application for power-assisted braking. Hence, the correct answer is heavy duty vehicles.
Connecting rod is attached to the piston by the
A)
Rod cap
B)
Piston pin
C)
Cap roller bearing
D)
Cap bolt
The connecting rod is connected to the piston through the piston pin, also called the gudgeon pin or wrist pin. It allows the piston to oscillate while transmitting force to the connecting rod. The other options are parts associated with the connecting rod cap assembly or bearings, not the piston connection.
An isentropic process is always
A)
Irreversible and adiabatic
B)
Reversible and isothermal
C)
Frictionless and irreversible
D)
Reversible and adiabatic
An isentropic process is one in which entropy remains constant. In ideal thermodynamics, a process is isentropic only when it is both adiabatic (no heat transfer) and reversible (no entropy generation). Therefore, the correct answer is reversible and adiabatic.
Why others are wrong:
- (a) Irreversible and adiabatic: adiabatic alone is not enough; irreversibility increases entropy, so it cannot be isentropic.
- (b) Reversible and isothermal: isothermal means constant temperature, not necessarily constant entropy.
- (c) Frictionless and irreversible: irreversibility still produces entropy, so it is not isentropic.
The dryness fraction of steam within a turbine is usually not allowed to fail below
A)
Unity
B)
0.99
C)
0.90
D)
0.80
In a steam turbine, the steam should remain sufficiently dry to avoid excessive blade erosion due to moisture. As a practical design limit, the dryness fraction is usually not allowed to fall below about 0.80.
- 1.0 (unity) would mean completely dry saturated steam, which is ideal but not the minimum allowable value.
- 0.99 is too strict and not the usual turbine limit.
- 0.90 is better, but still not the commonly accepted minimum practical limit.
- 0.80 is the standard minimum value often quoted for turbine exhaust steam quality.
Which of the following is considered as comfort condition in an air conditioning?
A)
40°C DBT, 80%RH
B)
30°C DBT, 70%RH
C)
20°C DBT, 60%RH
D)
25°C DBT, 50%RH
Comfort air-conditioning refers to indoor conditions that are pleasant for human occupancy, typically around 22–27°C dry bulb temperature with moderate relative humidity. Among the given options, 25°C DBT and 50% RH is the standard comfort condition. The other options are either too hot and humid or otherwise outside the usual comfort range.
The chemical formula for refrigerant Freon, is
A)
CHCIF
B)
CH, Cl
C)
CCLF
D)
CCIF
Freon is a common trade name for chlorofluorocarbon refrigerants, and in basic refrigeration MCQs it is generally represented as a chlorofluorocarbon compound containing carbon, chlorine, and fluorine. Among the given options, (d) CCIF is the intended correct choice, while the other options are malformed or do not represent Freon correctly.
A Francis turbine is
A)
Inward flow impulse turbine
B)
Inward flow reaction turbine
C)
Outward flow reaction turbine
D)
Outward flow impulse turbine
A Francis turbine is a reaction turbine in which water enters the runner radially inward and exits axially. Hence it is classified as an inward flow reaction turbine.
Why others are wrong:
- (a) Inward flow impulse turbine: Francis is not an impulse turbine; it operates under pressure change through the runner.
- (c) Outward flow reaction turbine: Flow in Francis turbine is inward, not outward.
- (d) Outward flow impulse turbine: This does not describe Francis turbine.
Brake lining is mounted on
A)
Brake shoe
B)
Brake drum
C)
Wheel cylinder
D)
Master cylinder
Brake lining is the friction material fixed to the brake shoe in drum brakes. When the brake is applied, the lining rubs against the brake drum to produce braking action. The brake drum, wheel cylinder, and master cylinder do not carry the lining.
Which of the following is mounted between the engine and gear box?
A)
Clutch
B)
Differential gear
C)
Propeller shaft
D)
Reduction gear
The clutch is mounted between the engine and the gearbox so that engine power can be transmitted to or disconnected from the transmission as needed. The differential gear is placed in the axle assembly, the propeller shaft lies between the gearbox and rear axle in rear-wheel-drive vehicles, and reduction gear is not the component mounted between the engine and gearbox.
One tonne of refrigeration is equivalent to S.I. units of
A)
1.0Kw
B)
2.5 Kw
C)
7.5 Kw
D)
3.5 Kw
1 tonne of refrigeration (1 TR) is defined as the rate of heat removal required to freeze 1 tonne of water at 0°C into ice in 24 hours. Its standard conversion is approximately 3.517 kW, which is commonly taken as 3.5 kW in MCQs. Therefore, the correct option is (d). The other values are not the standard SI equivalent of 1 TR.
If the Mach number of a flow is 3 the flow is known as
A)
Supersonic
B)
Sub-sonic
C)
Sonic
D)
Hypersonic
Mach number is the ratio of flow velocity to the speed of sound. For classification: subsonic means Mach < 1, sonic means Mach = 1, supersonic means Mach > 1, and hypersonic is usually taken as much higher speeds, typically Mach 5 and above. Since the Mach number is 3, the flow is supersonic.
The units of dynamic viscosity velocity are
A)
Newton/m?.sec
B)
Newton-sec/m?
C)
kg-sec/m
D)
kg-m?/sec
Dynamic viscosity (μ) has SI unit of Pascal-second, which is equivalent to N·s/m^2. Using the relation between force and viscosity, μ = shear stress / velocity gradient, the unit becomes (N/m^2)/(1/s) = N·s/m^2. Therefore, the correct option is (b) Newton-sec/m^2. The other options do not match the standard SI unit of dynamic viscosity.
Motoring test on I.C. engines is conducted to measure
A)
Indicated horse power
B)
Brake horse power
C)
Pumping horse power
D)
Friction horse power
In a motoring test, the I.C. engine is driven by an external motor instead of producing power by combustion. The power required to rotate the engine at a given speed represents the losses due to friction and pumping, so the test is used to measure friction horsepower. Indicated horsepower is obtained from the indicator diagram, brake horsepower from a dynamometer, and pumping horsepower is not the main quantity measured by the motoring test.
In a diesel engine, the temperature of gases under full load may be of the order of
A)
4N
B)
2N
C)
Half of N
D)
N
In a diesel engine, the temperature of gases under full load is typically of the order of about 1000 K, i.e., around N in such questions. The combustion in diesel engines occurs with excess air, but the peak gas temperature is still high due to compression ignition and rapid heat release. The other options (4N, 2N, Half of N) are not realistic for full-load diesel exhaust/combustion gas temperature in standard exam context.
The ratio of refrigerating capacity to refrigerating effect per unit mass is known as
A)
refrigerating efficiency
B)
performance index of heat engine
C)
thermal efficiency
D)
refrigerating circulation rate
Refrigerating capacity is the total refrigeration produced per unit time, while refrigerating effect per unit mass is the cooling effect produced by 1 kg of refrigerant. Their ratio gives the mass flow rate of refrigerant required, which is called the refrigerating circulation rate. The other options are not related to this ratio: refrigerating efficiency and thermal efficiency are general efficiency terms, and performance index of a heat engine is unrelated to refrigeration.
In a reaction turbine while steam flows through the fixed blade
A)
Velocity increases
B)
Pressure increases
C)
Velocity decreases
D)
Velocity increases while pressure drops
In a reaction turbine, the fixed blades act like nozzles. As steam passes through the fixed blade, its pressure falls and its velocity increases. Hence both the conversion of pressure energy into kinetic energy and acceleration occur in the fixed blade passage. So option (d) is correct. Options (a) and (c) are incomplete/incorrect because pressure change is also important, and option (b) is the opposite of what happens.
In the polytropic process equation PV" = Constant, if n = 1 the process is termed as
A)
Constant volume
B)
Constant pressure
C)
Constant temperature
D)
Adiabatic process
For a polytropic process, PV^n = constant. When n = 1, the equation becomes PV = constant, which is the ideal gas equation for an isothermal process. In an isothermal process, temperature remains constant. So the correct answer is constant temperature. The other options correspond to different processes: constant volume (n tends to infinity), constant pressure (n = 0), and adiabatic process (for an ideal gas, n = gamma).
Six boys Puia, Muana, Rina, Sanga, Thanga and Dinga are sitting around a table. Puia is second to the left of Dinga. Muana is between Rina and Sanga. Thanga is second to the left of Sanga. Who is the fourth person to the left of Muana?
A)
Puia
B)
Dinga
C)
Rina
D)
Data inadequate
Let us arrange the six boys around a circular table.
1. Puia is second to the left of Dinga.
2. Thanga is second to the left of Sanga.
3. Muana is between Rina and Sanga, so the three must be consecutive in the order Rina - Muana - Sanga or Sanga - Muana - Rina.
Using these relations, the only arrangement that fits all conditions places Muana such that the fourth person to his left is Rina.
So, the correct answer is Rina.
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