← MES Jr. Grade
Past Questions — 2020
Specific capacity in connection with Ground water is :-
A)
a constant for a given well
B)
depends on aquifer characteristics only
C)
increases with discharge rate
D)
decreases with time from the start of pumping
Specific capacity of a well is the discharge per unit drawdown (Q/s). As pumping continues, drawdown usually increases due to cone of depression and aquifer losses, so the ratio Q/s generally decreases with time. Hence it is not a constant for a well, not dependent on aquifer characteristics only, and not something that increases with discharge rate.
The Capacity factor of hydro-power plant will be identical with the load factor when :-
A)
Peak load is less than plant capacity
B)
Peak load equals to plant capacity
C)
Peak load is less than utilization factor
D)
Peak load equals to utilization factor
Capacity factor = (average load / plant capacity) and load factor = (average load / peak load). These two become identical when the denominator is the same in both expressions, i.e., when peak load equals plant capacity. Then both ratios reduce to average load / plant capacity. Option (a) is not necessary for equality, and (c) and (d) are incorrect because utilization factor is not the condition for equality here.
Air vessel in reciprocation pump is provided to :-
A)
have continuous uniform rate supply of liquid from a single acting pump
B)
have a uniform rate of liquid in delivery stroke for a single acting pump
C)
have both (a) & (b)
D)
prevent possible air lock during operation of the pump
An air vessel in a reciprocating pump serves two main purposes: (1) it makes the discharge more uniform by providing a continuous, nearly steady supply of liquid from a single-acting pump, and (2) it helps maintain a more uniform rate of liquid flow during the delivery stroke. Therefore, both statements (a) and (b) are correct. Option (d) is incorrect because preventing air lock is not the primary function of an air vessel in a reciprocating pump.
Choose the correct answer from the following :-
A)
Turbine with highest permissible specific speed is not preferable
B)
Higher specific speed turbine is generally more liable to cavitations
C)
Turbine with higher specific speed will be relatively bigger in size
D)
Higher the specific speed of turbine, higher will be the relative costs
Specific speed is the speed of a geometrically similar turbine that would produce unit power under unit head. As specific speed increases, the turbine generally operates at lower head and higher discharge, which increases the risk of cavitation. Therefore, statement (b) is correct.
Why others are incorrect:
(a) A higher permissible specific speed can actually be desirable depending on the application; the statement is not generally true.
(c) Higher specific speed turbines are usually more compact, not bigger in size.
(d) Higher specific speed does not necessarily mean higher relative cost; in fact, compact high-specific-speed turbines may be economical in suitable conditions.
In order to accelerate the flow of compressible fluid at super-sonic velocity, the flow passage must :-
A)
remain a uniform cross-section
B)
converge
C)
diverge
D)
flow passage does not have any effect
For compressible flow at supersonic speed, increasing velocity requires a diverging passage. In a converging nozzle, subsonic flow accelerates, but supersonic flow decelerates. Therefore, to accelerate a supersonic compressible fluid, the flow passage must diverge. Option (a) is incorrect because a uniform area does not provide the necessary acceleration mechanism. Option (b) is incorrect because convergence accelerates subsonic flow, not supersonic flow. Option (d) is incorrect because the passage shape clearly affects compressible-flow velocity.
In calculating NPSH values of hydraulic pump, pressure to be considered is :-
A)
Minimum anticipated barometric pressure
B)
Maximum anticipated vapour pressure
C)
Maximum anticipated pressure of both barometric and vapour pressure
D)
Minimum anticipated barometric pressure and maximum anticipated vapour pressure
NPSH (Net Positive Suction Head) depends on the pressure available at the pump suction. For safe pump operation, we consider the worst-case condition: the barometric pressure should be taken at its minimum anticipated value, and the vapour pressure of the liquid at its maximum anticipated value. This gives the least available NPSH and helps avoid cavitation. Therefore, option (d) is correct. Options (a), (b), and (c) are incomplete or incorrect because NPSH calculation must account for both the minimum atmospheric pressure and maximum vapour pressure together.
The method of evaporation estimation involving writing the hydrological continuity equation for the lake and determining the evaporation from a knowledge or estimation of other variables is :-
A)
Energy-Budget method
B)
Mass-Transfer method
C)
Water-Budget method
D)
Colorado Sunken pan method
The method described uses the hydrological continuity equation for a lake and estimates evaporation as the unknown term after accounting for inflow, outflow, rainfall, seepage, and change in storage. This is the Water-Budget method. The Energy-Budget method is based on heat balance, the Mass-Transfer method on vapor transport by wind, and the Colorado Sunken pan method is a pan evaporation measurement technique.
The canal outlet in which the discharge is affected by fluctuation in water level of distributing channel but not affected by water level fluctuation of the field channel is :-
A)
Non-modular outlet
B)
Flexible outlet
C)
Rigid module
D)
Both (b) & (c)
A rigid module outlet is designed so that its discharge depends on the water level in the distributing channel, but it is not affected by fluctuations in the water level of the field channel. Hence it matches the given description.
Why the others are incorrect:
- Non-modular outlet: discharge is affected by water levels on both sides.
- Flexible outlet: discharge is generally affected by the water level in the field channel as well.
- Both (b) & (c): only rigid module fits the statement, not flexible outlet.
In a hydraulic structure where a supercritical stream meets a subcritical stream of sufficient depth, there will be :-
A)
No change in the energy
B)
No flow of stream possible
C)
Magnification of energy
D)
Dissipation of energy
When a supercritical stream meets a subcritical stream of sufficient depth, a hydraulic jump forms. In a hydraulic jump, part of the kinetic energy is converted into turbulence and heat, so there is a significant loss of energy. Therefore, the correct answer is dissipation of energy. The other options are incorrect because energy is not conserved across the jump, flow is certainly possible, and energy does not increase.
A linear reservoir is one in which :-
A)
the volume varies linearly with elevation
B)
the storage varies linearly with the outflow rate
C)
the storage varies linearly with time
D)
the storage varies linearly with the inflow rate
A linear reservoir is defined by a linear storage-discharge relationship, i.e., storage S is directly proportional to outflow Q. Hence, as outflow changes, storage changes linearly with it. Option (a) refers to a storage-elevation relationship, and (c) and (d) are not the defining properties of a linear reservoir.
A reservoir primarily used to store the excess water during the period of large supplies and release it gradually as and when it is needed is :-
A)
Storage reservoir
B)
Flood control reservoir
C)
Distribution reservoir
D)
Multipurpose reservoir
A storage reservoir is designed to retain excess water during periods of high inflow or large supply and then release it gradually when required. A flood control reservoir is mainly meant to reduce flood peaks, a distribution reservoir stores water for immediate distribution in a supply system, and a multipurpose reservoir serves several functions at once. Hence, the correct answer is Storage reservoir.
The actual thermodynamic process which is approximated by the relation pvn = Constant, where n is a positive constant is called :-
A)
Isothermal process
B)
Adiabatic process
C)
Polytropic process
D)
Isentropic process
The relation pV^n = constant, where n is a positive constant, defines a polytropic process. Many real thermodynamic processes can be approximated by this equation depending on the value of n. For example, n = 1 gives an isothermal process, and n = γ gives an adiabatic process. Therefore, the correct answer is polytropic process.
In the principle of plain sedimentation, discrete particles having settling velocity lower than SOR are
A)
entirely removed
B)
partially get removed
C)
remain in suspension
D)
removed in direct proportion to the ratio of their settling velocity and vertical velocity
In plain sedimentation, a particle is fully removed only if its settling velocity is greater than or equal to the surface overflow rate (SOR). If its settling velocity is lower than SOR, only a fraction of the particles will settle out before leaving the tank, so they are partially removed. Hence, option (b) is correct. Option (a) is wrong because complete removal does not occur. Option (c) is wrong because such particles do not all remain in suspension. Option (d) is not the general principle for discrete settling in plain sedimentation.
Pelton wheel turbine is an example of :-
A)
Mix flow turbine
B)
Axial flow turbine
C)
Radial flow turbine
D)
Tangential flow turbine
A Pelton wheel is an impulse turbine in which the water jet strikes the buckets tangentially to the runner. Hence it is classified as a tangential flow turbine. Mix flow, axial flow, and radial flow turbines describe other turbine flow directions, not the Pelton wheel.
The frictional resistance in the laminar flow through pipes is independent of :-
A)
Nature of the surface in contact
B)
Velocity of flow
C)
Area of surface in contact
D)
Temperature of the flowing fluid
In laminar flow through pipes, frictional resistance is governed mainly by the viscosity of the fluid and the velocity distribution. It is directly related to the velocity of flow and the area of surface in contact, and it also varies with temperature because temperature changes viscosity. In ideal laminar pipe flow, the frictional resistance is independent of the nature of the surface in contact, provided the pipe is hydraulically smooth and the flow remains laminar. Hence, option (a) is correct.
If the allowable degree of error in the estimate of the mean rainfall is 10% and the co-efficient of variation of the rainfall values at the existing stations in percentage is 30, the optimum number of Raingauge stations in the catchment area would be :-
A)
3
B)
6
C)
8
D)
9
For estimating the optimum number of raingauge stations, the formula is N = (Cv / Pe)^2, where Cv is the coefficient of variation (%) and Pe is the allowable percentage error. Here, Cv = 30 and Pe = 10, so N = (30/10)^2 = 3^2 = 9. Hence, the optimum number of raingauge stations is 9. The other options do not satisfy the standard hydrology formula.
If river flow permits, the hydro-power plant that can operate both as peak-load and base-load plant is :-
A)
Run-of-river plant with pondage
B)
Pumped storage plant
C)
Reservoir plant
D)
Tidal plants
A reservoir hydro-power plant can store a large quantity of water and regulate discharge as needed. Because of this storage, it can generate continuously as a base-load plant and also supply extra power during peak demand. A run-of-river plant with pondage has only limited storage, so its peaking ability is restricted. A pumped storage plant is mainly used for peak-load support, not as a true base-load plant. Tidal plants depend on tidal cycles and are not suitable for both base-load and peak-load operation.
Which of the following factor(s) will influence the selection of type of turbine in Hydel project:-
A)
Water Quantity required
B)
The variability of load
C)
The rotational speed of turbine
D)
All of these
The selection of a turbine for a hydel project depends on multiple factors. Water quantity required affects whether an impulse or reaction turbine is suitable; variability of load influences the type of turbine chosen to handle changing demand efficiently; and the required rotational speed of the turbine also affects the selection because different turbines operate best at different speed ranges. Therefore, all the given factors influence turbine selection.
The conversion of compressible fluid from super-sonic flow to a sub-sonic flow is always accompanied by a sudden :-
A)
increase in velocity
B)
decrease in density
C)
increase in pressure
D)
increase in both pressure and density
In compressible flow, when a supersonic flow is brought to subsonic flow suddenly, it occurs through a shock wave. Across a normal shock, velocity decreases abruptly, while pressure, density, and temperature all increase. Therefore, the conversion from supersonic to subsonic flow is always accompanied by a sudden increase in both pressure and density. Options (a) and (b) are opposite to the actual behavior, and (c) is incomplete because density also increases.
If the working head available in hydro-power plant is less than 30 m, which of the following turbine would be suitable for the project :-
A)
Pelton wheel
B)
Turgo-impule wheel
C)
Kaplan turbine
D)
Modern Francis turbine
Hydraulic turbines are selected according to available head. Kaplan turbines are low-head, high-discharge turbines, typically suitable for heads below about 30 m. Pelton wheel and Turgo impulse wheel are impulse turbines used for high-head sites, while Francis turbines are generally used for medium heads, not the lowest-head range. Therefore, for working head less than 30 m, the correct choice is Kaplan turbine.
In a compressible fluid flow where the velocity of flow is reduced to zero and the kinetic energy is converted into pressure energy is the :-
A)
Mach line
B)
Stagnation point
C)
Zone of silence
D)
Zone of action
In compressible flow, when the fluid velocity becomes zero, the moving fluid is brought to rest and its kinetic energy is converted into pressure energy. This location is called a stagnation point.
Why others are incorrect:
- (a) Mach line: a line associated with Mach waves in supersonic flow.
- (c) Zone of silence: region outside the Mach cone where disturbance has not reached.
- (d) Zone of action: not the term used for this condition in fluid mechanics.
So, the correct answer is stagnation point.
Which of the followings is not an accessories of an intake structure of Hydro-power plant :-
A)
Rakes
B)
Penstock closing gates with hoist
C)
Forebay
D)
Trash rack
An intake structure of a hydropower plant commonly includes accessories such as trash racks, rakes, and sometimes a forebay as part of the water-conveyance and screening arrangement. A penstock closing gate with hoist, however, is associated with the penstock/control arrangement, not the intake structure itself. Therefore, it is the item that is not an accessory of the intake structure.
The simplest multi-cellular micro-organism that require a relatively high dissolved oxygen and that their presence is a good indication of relative stability of a treated waste is:-
A)
Rotifers
B)
Algae
C)
fungi
D)
Protozoa
Rotifers are among the simplest multicellular microorganisms found in well-treated wastewater. They require relatively high dissolved oxygen and their presence indicates that the treated waste is relatively stable. Algae are photosynthetic organisms, fungi are not typically used as an indicator of treated waste stability, and protozoa are unicellular rather than multicellular.
At what temperature that sewage will change from fresh to stale in 2 to 6 hours :-
A)
about 15oC
B)
about 18oC
C)
about 20oC
D)
about 22oC
In sewage engineering, the rate of septic decomposition increases with temperature. Standard environmental engineering texts note that sewage may change from fresh to stale in about 2 to 6 hours at around 20°C. At lower temperatures this change takes longer, while at higher temperatures it occurs faster. Hence, the correct option is (c) about 20°C.
The water contamination that may be concentrated by Algae or other water organism and upon eaten by fishes can get further concentration is :-
A)
Lead
B)
Radioactive isotopes
C)
Fluoride
D)
Mercury
This refers to bioaccumulation/biomagnification in aquatic food chains. Certain contaminants are taken up by algae and small organisms, then become more concentrated in fish that eat them. Mercury is a classic example, especially as methylmercury. Lead and fluoride do not characteristically biomagnify this way, and radioactive isotopes are not the standard answer to this specific water-contamination question.