← Departmental (other)
Past Questions
In electrical instruments, what is typically the most efficient form of damping?
A)
Air damping
B)
Fluid friction
C)
Eddy currents
D)
Magnetic friction
Option C is correct: Eddy currents.
Which devices are connected directly to the secondary of a Current Transformer?
A)
Voltmeters and potential coils of wattmeters
B)
Ammeters and current coils of wattmeters
C)
Frequency meters
D)
Power factor indicators
Option B is correct: Ammeters and current coils of wattmeters.
What is the ideal/acceptable value of earth resistance for a standard electrical installation?
A)
50 Ohms
B)
25 Ohms
C)
1 Ohm
D)
100 Ohms
Option C is correct: 1 Ohm.
What is the property of magnetic materials?
A)
resistivity
B)
conductivity
C)
permeability
D)
ductility
Option C is correct: permeability.
What is the primary purpose of earthing?
A)
To increase the resistance of the circuit
B)
To prevent electric shock by providing a low-resistance path for faulty current
C)
To increase the power factor of the system
D)
To protect against over-currents only
Option B is correct: To prevent electric shock by providing a low-resistance path for faulty current.
How is a Potential Transformer (PT) connected in a power system?
A)
In series with the load
B)
In parallel with the line being measured
C)
In series-parallel
D)
Across the neutral only
Option B is correct: In parallel with the line being measured.
The maximum free water cement ratio in RCC water tank is:
A)
0.35
B)
0.40
C)
0.45
D)
0.50
In the design of water-retaining structures (RCC water tanks), the primary objective is to ensure 'watertightness' and durability against seepage. According to standard codes of practice (such as IS 3370), the permeability of the concrete must be kept very low to prevent leakage and protect the reinforcement from corrosion. To achieve a dense, impermeable concrete matrix, the water-cement (w/c) ratio must be strictly limited. While very low ratios (0.35-0.40) are excellent for durability, the standard maximum permissible free water-cement ratio generally accepted for RCC water tanks to balance workability and impermeability is 0.45. Ratios higher than 0.45 (like 0.50) increase the porosity of the concrete, leading to higher permeability and a higher risk of leakage, making them unsuitable for liquid-retaining structures.
Grit chambers of sewage plant are usually changed after:
A)
1 day
B)
1 week
C)
2 weeks
D)
4 weeks
In a sewage treatment plant, grit chambers are designed to remove inorganic solids (such as sand, gravel, and eggshells) through sedimentation. These materials are non-biodegradable and highly abrasive. If allowed to accumulate for long periods, they can cause significant wear and tear on downstream pumps, clog pipes, and reduce the effective volume of subsequent treatment units (like primary clarifiers). Therefore, to maintain operational efficiency and prevent equipment damage, grit chambers are typically cleaned or 'changed' (emptied of accumulated grit) on a daily basis. Options b, c, and d (1 week to 4 weeks) are incorrect because allowing grit to accumulate for such durations would lead to operational failure and excessive mechanical wear.
The chemical reaction between cement and water is called:
A)
Watering
B)
Cement hydration
C)
Cement paste
D)
Cementing
The chemical process that occurs when cement is mixed with water is known as hydration. During this process, the compounds in the cement (primarily tricalcium silicate and dicalcium silicate) react chemically with water to form a hard, stone-like mass of hydrated compounds (such as Calcium Silicate Hydrate or C-S-H gel) and calcium hydroxide. This reaction is exothermic and is responsible for the setting and hardening of concrete.
Analysis of other options:
- (a) Watering: This is a general term for adding water and not a technical chemical term for the reaction.
- (c) Cement paste: This refers to the physical mixture of cement and water, not the chemical reaction itself.
- (d) Cementing: This is a general term for the act of joining materials together using cement, not the specific chemical process.
Which of the following statement is wrong?
A)
The water carriage system is more hygienic
B)
There is no smell or sight nuisance in the case of water carriage system
C)
The sewers in the water carriage system being all underground do not impair the beauty of the place
D)
The initial cost of construction of water carriage system is very low
The question asks to identify the WRONG statement regarding the water carriage system of sewerage.
1. Statement (a) is correct: The water carriage system is considered the most hygienic because waste is transported quickly via water to a treatment plant, minimizing human contact with sewage.
2. Statement (b) is correct: Because the waste is enclosed in pipes and transported rapidly, there is minimal smell or sight nuisance compared to dry systems or open drains.
3. Statement (c) is correct: Since the network of sewers is laid underground, it does not interfere with the surface aesthetics or the beauty of the urban landscape.
4. Statement (d) is incorrect: The water carriage system requires extensive excavation, the laying of high-quality pipes, the construction of manholes, and the establishment of a sewage treatment plant (STP). Consequently, the initial capital investment (construction cost) is very high compared to simpler systems like the dry system or pit latrines. Therefore, stating that the cost is 'very low' is factually wrong.
The breaking up of cohesion in a mass of concrete is called:
A)
Workability
B)
Bleeding
C)
Segregation
D)
Creep
Step-by-step reasoning:
1. Definition of Segregation: Segregation in concrete occurs when the coarse aggregates separate from the cement paste (mortar). This represents a loss of homogeneity and a 'breaking up of cohesion' within the concrete mass, often caused by over-vibration, dropping concrete from a height, or improper mix design.
2. Analysis of other options:
- Workability (a): This refers to the ease with which concrete can be mixed, placed, consolidated, and finished. It is a property of fresh concrete, not a failure of cohesion.
- Bleeding (b): This is a specific form of segregation where water (a liquid) rises to the surface of freshly placed concrete. While related to segregation, bleeding refers specifically to the movement of water, whereas the general breaking up of cohesion of the mass is termed segregation.
- Creep (d): This is the time-dependent permanent deformation of concrete under a sustained constant load. It is a long-term structural property, not a phenomenon occurring during the fresh state of concrete.
3. Conclusion: The process of the concrete mass losing its cohesive unity and separating into its constituent parts is defined as segregation.
In india per capita contribution of dry solids to be assumed at:
A)
40 g/day
B)
50 g/day
C)
60 g/day
D)
70 g/day
In Environmental Engineering, specifically regarding the design of sewage treatment plants and the estimation of sludge production, the per capita contribution of dry solids (suspended solids) to domestic sewage is a critical parameter. According to standard Indian standards and textbooks on Environmental Engineering (such as those by S.K. Garg or B.C. Punmia), the average per capita contribution of dry solids in India is generally assumed to be approximately 70 grams per day. This value is used to calculate the total organic load and the volume of sludge that needs to be handled in waste water treatment processes. Options a, b, and c (40g, 50g, and 60g) are lower than the standard design assumption used for Indian urban populations.
A combined system of sewer will be favourable when:
A)
The sewers are to be laid in rocks
B)
The finance are limited
C)
The topography is flat necessitating deep excavation for combined system
D)
The locality to be served has narrow streets
A combined sewer system carries both domestic sewage and storm water in a single pipe, whereas a separate system requires two distinct sets of pipes.
1. Why Option (d) is correct: In areas with narrow streets, there is insufficient physical space to lay two separate parallel pipelines (one for sewage and one for storm water) without causing extreme congestion or interfering with other utilities. A single combined pipe is the most practical solution in such constrained urban environments.
2. Why Option (a) is incorrect: Laying sewers in rock is expensive and difficult. A combined system requires much larger diameter pipes to handle peak storm flows compared to a separate sanitary sewer. Excavating larger trenches in rock is significantly more costly than excavating smaller ones.
3. Why Option (b) is incorrect: While it might seem that one pipe is cheaper than two, combined systems often require much larger pipes and massive treatment plants capable of handling huge volumes of diluted sewage during rains, which can increase long-term capital and operational costs.
4. Why Option (c) is incorrect: In flat topography, deep excavation is already a challenge. Because combined sewers must be larger to accommodate storm water, they often require deeper excavations to maintain the necessary gradient (slope) for gravity flow, making them less favorable in flat terrains compared to separate systems.
For large sewers , the maximum distance between manholes should be:
A)
75 m
B)
100 m
C)
200 m
D)
300 m
In environmental engineering and sewage system design, manholes are provided at regular intervals to allow for inspection, cleaning, and removal of obstructions. The spacing of manholes depends primarily on the diameter of the sewer pipe. For small sewers (typically diameters up to 600mm or 900mm), the spacing is shorter (often 30m to 100m). However, for large sewers (trunk sewers or intercepting sewers), the distance can be increased because they are less prone to frequent localized blockages and are often constructed with materials and gradients that facilitate easier flow. According to standard engineering practice and various municipal codes (such as CPHEEO manuals), the maximum distance between manholes for large sewers is generally taken as 300 meters. Options a, b, and c are typical spacings for smaller diameter lateral or branch sewers.
One cubic metre of water weighs:
A)
100 litres
B)
250 litres
C)
500 litres
D)
1000 litres
Step-by-step reasoning:
1. Understanding the units: The question asks for the 'weight' (though it uses volume units in the options) of one cubic metre (1 m³) of water.
2. Volume Conversion: By definition, 1 cubic metre is equal to 1,000 litres (1 m³ = 1000 L).
3. Mass/Weight Relationship: For pure water at standard temperature and pressure, the density is approximately 1000 kg/m³. Therefore, 1 m³ of water has a mass of 1000 kg.
4. Litre-to-Mass Correlation: Since 1 litre of water weighs approximately 1 kilogram, 1000 litres of water weigh 1000 kilograms.
5. Analysis of Options: The options provided are in 'litres', which is a unit of volume. In the context of basic fluid mechanics questions of this type, the question is testing the fundamental conversion between cubic metres and litres.
- Option a (100 L), b (250 L), and c (500 L) are mathematically incorrect conversions of 1 m³.
- Option d (1000 L) correctly identifies the volume equivalent of 1 m³ of water.
The structure constructed in the form of a chamber and provided along the sewer line to admit clear rain water free from suspended and floating materials into the combined sewer is called:
A)
Manhole
B)
Flushing tanks
C)
Catch basin
D)
Drainage trap
A catch basin is a specialized structure used in combined sewer systems. It consists of a chamber (sump) constructed at the inlet of the sewer line from the street. Its primary function is to act as a grit chamber; as rainwater enters, the heavier suspended solids, floating debris, and grit settle to the bottom of the basin, allowing only the relatively clear water to enter the main sewer line. This prevents the sewer from becoming clogged with street debris.
Why other options are incorrect:
- a. Manhole: These are access points used for inspection, cleaning, and maintenance of the sewer line, not specifically for filtering rainwater.
- b. Flushing tanks: These are used in sewers with flat gradients to provide a sudden surge of water to flush out accumulated solids.
- d. Drainage trap: Traps are used in plumbing to prevent sewer gases from entering buildings by maintaining a water seal; they are not used for admitting rainwater into combined sewers.
The minimum depth of septic tank is considered to be:
A)
0.5 m
B)
1.0 m
C)
1.2 m
D)
1.5 m
In Environmental Engineering, a septic tank is designed to provide sufficient detention time for the settling of solids and anaerobic digestion of organic matter. According to standard engineering guidelines (such as IS 2470 in the Indian context), the liquid depth of a septic tank is typically maintained between 1.0 m and 1.8 m. The minimum liquid depth is specified as 1.0 m to ensure that there is enough space for the accumulation of sludge at the bottom and the formation of a scum layer at the top without compromising the hydraulic retention time or causing premature solids carry-over into the soak pit or drainage field. Options a (0.5 m) is too shallow to prevent turbulence and allow settling; options c (1.2 m) and d (1.5 m) are common design depths but are not the absolute minimum threshold.
Venturimeter is used to:
A)
Measure the velocity of a flowing liquid
B)
Measure the pressure of a flowing liquid
C)
Measure the discharge of liquid flowing in a pipe
D)
Measure the pressure of difference of liquid flowing between two points in a pipe line
A Venturimeter is a device used for measuring the discharge (volumetric flow rate) of a fluid flowing through a pipeline. It works on the principle of Bernoulli's Equation. The device consists of a converging section, a throat, and a diverging section. As the fluid passes through the throat (the narrowest part), its velocity increases and its pressure decreases. By measuring the pressure difference between the inlet and the throat using a manometer, the flow rate (discharge) can be calculated using the formula: Q = Cd * A1 * sqrt((2gh) / (1 - (A1/A2)^2)), where Cd is the coefficient of discharge, A1 is the inlet area, and h is the differential pressure head.
Why other options are incorrect:
- Option (a): While velocity changes within the meter, the primary purpose of the device is to find the total discharge (Q), not just the velocity at a point.
- Option (b): A pressure gauge or manometer is used to measure pressure; the Venturimeter uses pressure differences as a means to find flow rate.
- Option (d): While the Venturimeter creates a pressure difference, it is not used to 'measure the pressure difference' as its end goal, but rather uses that difference to calculate the discharge.
A pipe installed for ventilation purpose is called:
A)
Waste pipe
B)
Soil pipe
C)
Vent pipe
D)
Anti-siphonage pipe
In plumbing and environmental engineering, different pipes serve specific functions within a drainage system:
1. **Vent Pipe (Correct):** A vent pipe is specifically installed to provide ventilation to the drainage system. Its primary purpose is to allow sewer gases to escape to the atmosphere and to admit fresh air into the system, which prevents the buildup of pressure and ensures the smooth flow of waste.
2. **Waste Pipe:** This pipe is used to carry liquid waste (greywater) from fixtures like washbasins, sinks, and baths, but it does not carry human excreta.
3. **Soil Pipe:** This pipe is designed to carry human excreta (blackwater) from water closets (WCs) and urinals to the main sewer line.
4. **Anti-siphonage Pipe:** While this is a type of vent pipe, it is a specialized pipe used specifically to prevent the 'siphoning' (suction) of water seals in traps, ensuring that sewer gases do not enter the building. However, the general term for a pipe installed for ventilation purpose is the 'Vent pipe'.
The quantity of liquid waste which flows in sewers during rainy season is called:
A)
Storm sewage
B)
Dry weather flow
C)
Sanitary sewage
D)
Domestic waste
In environmental engineering and wastewater management, sewage is categorized based on its source and the weather conditions.
1. **Storm Sewage (Correct):** This refers to the wastewater that enters the sewer system specifically due to precipitation (rain or melting snow). In combined sewer systems, the total flow during the rainy season is the sum of dry weather flow and storm sewage.
2. **Dry Weather Flow (DWF):** This is the average flow of sewage in a sewer during periods of no rainfall. It consists primarily of domestic sewage and industrial waste.
3. **Sanitary Sewage:** This is a general term for wastewater from toilets, sinks, and showers (domestic waste), regardless of the season. While it flows during the rainy season, it is not the specific term for the *additional* liquid waste caused by rain.
4. **Domestic Waste:** This refers to the waste generated from residential activities, which is a component of sanitary sewage, not the rain-induced flow.
Therefore, the liquid waste that flows specifically due to the rainy season is termed 'Storm sewage'.
Which of the following statement is correct?
A)
Sewage if not treated, will create healthy conditions
B)
Secondary treatment of sewage works on hydraulic separation principles
C)
Primary clarifiers are the sedimentation tanks located just after the grit chambers
D)
Trickling filter is different from percolating filter
Step-by-step analysis of the options:
1. Option (a) is incorrect: Untreated sewage contains pathogens, organic matter, and toxic chemicals. If not treated, it leads to water pollution, outbreaks of diseases (like cholera and typhoid), and eutrophication, creating unhealthy conditions, not healthy ones.
2. Option (b) is incorrect: Secondary treatment is a biological process (e.g., Activated Sludge Process, Trickling Filters) that uses microorganisms to decompose organic matter. Hydraulic separation (physical removal of solids based on density/gravity) is the principle used in Primary treatment.
3. Option (c) is correct: In a typical wastewater treatment plant flow, the sequence is: Screening $\rightarrow$ Grit Chamber $\rightarrow$ Primary Clarifier (Primary Sedimentation Tank). The grit chamber removes heavy inorganic solids (sand, gravel), and the primary clarifier follows to remove settleable organic solids.
4. Option (d) is incorrect: In the context of environmental engineering, a trickling filter is essentially a type of percolating filter. Both refer to attached-growth biological processes where sewage is sprayed over a bed of media (rocks, plastic) to allow a biofilm to degrade organic matter.
The activated sludge process of sewage treatment:
A)
Requires large area for construction of whole unit
B)
Requires higher water head for operation than trickling filters
C)
Has high efficiency
D)
Has low output
The Activated Sludge Process (ASP) is a biological wastewater treatment method that uses a mass of microorganisms (activated sludge) to decompose organic matter.
1. **Why Option (c) is correct:** ASP is known for its high efficiency in removing Biochemical Oxygen Demand (BOD) and suspended solids, often achieving removal rates of 90-95% or higher, which is generally superior to traditional trickling filters.
2. **Why Option (a) is incorrect:** Compared to waste stabilization ponds or extensive trickling filter beds, ASP is more compact and requires a smaller land area for the same volume of sewage treated.
3. **Why Option (b) is incorrect:** Trickling filters often rely on gravity flow through a medium, whereas ASP requires mechanical aeration (blowers/pumps). While ASP has higher energy requirements, it does not necessarily require a 'higher water head' for operation in the way a gravity-fed filter system does.
4. **Why Option (d) is incorrect:** ASP is designed for high-capacity treatment and can handle large volumes of sewage efficiently, meaning it has a high output capacity rather than a low one.
The natural processed in which the oxygen of water of streams is consumed by sewage and at the same time, it is replenish by the atmosphere this process is known as:
A)
Oxidation
B)
Deoxidation
C)
Self purification
D)
Sedimentation
The process described is known as 'Self Purification' of a stream. When sewage is discharged into a water body, aerobic bacteria decompose the organic matter, which consumes the dissolved oxygen (DO) in the water (a process called deoxygenation). Simultaneously, oxygen from the atmosphere is absorbed into the water through the surface (a process called reaeration). The balance between the rate of deoxygenation and the rate of reaeration allows the stream to naturally recover its quality over time and distance. This overall cycle is termed self-purification.
Why other options are incorrect:
- Oxidation (a): This is a chemical reaction part of the process, but not the name of the overall natural cycle of recovery.
- Deoxidation (b): This refers only to the removal or consumption of oxygen, not the replenishment part.
- Sedimentation (d): This is a physical process where suspended solids settle at the bottom due to gravity; it does not involve the oxygen exchange cycle described.
For house drainage and lateral connections we shall use:
A)
Cast iron sewers
B)
Concrete sewers
C)
Masonry sewers
D)
Stone ware sewers
In environmental engineering and urban drainage design, the selection of sewer material depends on the location, load, and chemical nature of the effluent.
1. **Stoneware (Vitrified Clay) Sewers**: These are the preferred choice for house drainage and lateral connections. They are highly resistant to chemical corrosion (especially from domestic sewage), have a smooth internal surface to prevent clogging, and are cost-effective for smaller diameters typically used in residential connections.
2. **Cast Iron Sewers (Option a)**: While very strong and leak-proof, they are expensive and primarily used for building drains (vertical stacks) or in areas where high structural strength is required, rather than standard lateral connections.
3. **Concrete Sewers (Option b)**: These are generally used for larger main sewers or trunk sewers due to their size and strength. They are more prone to corrosion by sulfuric acid (H2S) produced in sewage compared to stoneware.
4. **Masonry Sewers (Option c)**: These are outdated and used only for very large, old trunk sewers. They are not suitable for small-diameter house drainage due to leakage issues and high construction effort.
Land disposal of sewage will be favourable where:
A)
The rivers run dry or have a small flow during summer
B)
Rainfall is very high
C)
Climate is wet and rates of evaporation is low
D)
The sewage arriving at the out fall point is fresh and non-septic
Land disposal of sewage (such as sewage farming or land application) involves applying sewage to the soil for treatment and disposal. For this method to be favorable and effective, the following conditions must be met:
1. **Fresh Sewage (Option d):** Sewage must be 'fresh' and 'non-septic'. If sewage becomes septic (anaerobic) during transport, it develops foul odors (H2S gas) and becomes difficult to handle, making it unsuitable for land application near populated areas. Fresh sewage contains dissolved oxygen and organic matter that can be more effectively utilized by soil microbes and plants.
2. **Why Option a is incorrect:** If rivers run dry, it might make land disposal a *necessity* due to lack of water bodies for dilution, but it doesn't make the process of land disposal itself 'favorable' or technically efficient.
3. **Why Option b is incorrect:** Very high rainfall is detrimental to land disposal. Excessive rain leads to waterlogging, prevents the soil from absorbing the sewage, and increases the risk of sewage runoff contaminating nearby surface water bodies.
4. **Why Option c is incorrect:** A wet climate with low evaporation rates leads to saturation of the soil. For land disposal to work, the soil must have the capacity to absorb the liquid (percolation) and the environment should ideally support evaporation to prevent the water table from rising too high.