← Junior Engineer
Past Questions
The most important purpose of providing frog in a brick is to
A)
reduce weight of the brick
B)
improve insulation by providing hollows
C)
emboss manufacturer’s name
D)
to form a key for holding the mortar
A frog is the depression provided on one face of a brick. Its main purpose is to create a key so that mortar can grip the brick properly and the bond becomes stronger. It also helps in better laying of bricks with the frog facing upward. The other options are not the primary purpose: reducing weight and improving insulation are not the main functions, and embossing the manufacturer’s name is only an identification mark, not the most important purpose.
Which of the following processes is treated as a ‘loss’ in engineering hydrology?
A)
Infiltration
B)
Precipitation
C)
Percolation
D)
Transpiration
In engineering hydrology, a 'loss' refers to water removed from the surface water system before it becomes runoff. Transpiration is one such loss because water is taken up by plants and returned to the atmosphere. Infiltration and percolation are also losses in the broader hydrologic sense, but in standard MCQ context the process classically treated as a direct loss term is transpiration. Precipitation is not a loss; it is the input to the hydrologic system.
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 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.
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.
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.
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.
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).
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.
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.
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.
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 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.
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 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.
The steam in a boiler drum is always
A)
Wet
B)
Dry
C)
Superheated
D)
Dry and saturated
In a boiler drum, the steam collected is saturated steam at boiler pressure, and by design it is expected to be dry or nearly dry after separation of moisture. Steam in the drum is therefore not superheated. It is also not wet, because the purpose of the drum and steam separators is to remove entrained water droplets. Hence, the best answer is "dry and saturated."
The velocity of a fluid particle at the centre of the pipe section is
A)
Maximum
B)
Minimum
C)
Average
D)
Logarithmic average
In laminar or turbulent flow through a pipe, fluid velocity is zero at the wall due to no-slip condition and increases toward the centre. Therefore, the velocity at the centre of the pipe section is the maximum velocity. The average velocity is lower than the centre-line velocity, so options like minimum, average, or logarithmic average are incorrect.
Multistage centrifugal pump are used to
A)
give high discharge
B)
pump viscous liquids
C)
produce high heads
D)
and (b) together
A multistage centrifugal pump has two or more impellers mounted in series on the same shaft. The discharge from one stage becomes the inlet to the next, so the heads developed by individual stages add up. Therefore, multistage centrifugal pumps are used to produce a high head. They are not mainly meant for viscous liquids, and high discharge is generally not the distinguishing purpose of multistage pumps.
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 load on the motor and allows the pump to start without excessive power demand. After the pump reaches normal speed and develops sufficient pressure/head, the delivery valve is opened gradually. If it were open at starting, the motor could draw high current and the pump may not start properly. Hence, the correct answer is fully closed.
In a refrigeration cycle the heat is rejected by refrigerant at
A)
Evaporator
B)
Condenser
C)
Expansion valve
D)
Compressor
In a vapour-compression refrigeration cycle, the refrigerant absorbs heat in the evaporator and rejects heat to the surroundings in the condenser. The expansion valve only reduces pressure, and the compressor raises the pressure and temperature of the refrigerant. Therefore, heat is rejected by the refrigerant at the condenser.
Which type of turbine is different from the others?
A)
Pelton turbine
B)
Propeller turbine
C)
Kaplan turbine
D)
Francis turbine
Pelton turbine is different from the others because it is an impulse turbine, while Propeller, Kaplan, and Francis turbines are reaction turbines. Pelton works by converting the jet's kinetic energy directly into runner motion, whereas the others operate with pressure change through the runner.
In a Diesel engine the duration between the time of injection and time of ignition is called
A)
Explosion period
B)
Burning period
C)
Delay period
D)
Pre-ignition period
In a diesel engine, the time interval between the start of fuel injection and the start of ignition is called the ignition delay or delay period. This is the correct technical term used in IC engines. 'Explosion period' and 'burning period' refer to later stages of combustion, while 'pre-ignition period' is not the standard term for this interval in diesel engines.