← JE Departmental
Past Questions
What is the major advantage of ERW pipes?
A)
High flexibility
B)
Corrosion resistance
C)
Smooth surface and economical
D)
Fire resistance
ERW stands for Electric Resistance Welding. These pipes are manufactured by rolling a flat strip of steel into a cylindrical shape and welding the longitudinal seam using high-frequency electric current.
1. Why 'Smooth surface and economical' is correct: Because ERW pipes are produced from cold-rolled strips, they possess a very smooth internal and external surface finish, which reduces friction loss for fluids. Furthermore, the mass-production process of ERW is significantly more cost-effective (economical) compared to seamless pipes, which require complex piercing and drawing processes.
2. Why other options are incorrect:
- High flexibility (a): Steel pipes, including ERW, are rigid. Flexibility is a characteristic of plastics (like HDPE) or rubber, not ERW steel.
- Corrosion resistance (b): Standard ERW pipes are made of carbon steel and are highly susceptible to corrosion unless they are galvanized or coated. Corrosion resistance is a property of stainless steel or PVC.
- Fire resistance (d): While steel is non-combustible, 'fire resistance' is a general property of most metals and not a specific 'major advantage' unique to the ERW manufacturing process compared to other steel pipes.
Which one of the following is not a coagulant used in water treatment plant?
A)
Polyaluminum Chloride (PAC)
B)
Ferric Chloride
C)
Aluminum sulphate(Alum)
D)
Bleaching powder
Coagulants are chemicals added to water to neutralize the electrical charge of colloidal particles, allowing them to clump together (flocculate) and settle out of the water.
1. Polyaluminum Chloride (PAC) is a high-efficiency inorganic polymer coagulant widely used in modern water treatment.
2. Ferric Chloride (FeCl3) is a common iron-based coagulant used to remove turbidity and organic matter.
3. Aluminum sulphate (Alum) is the most traditional and widely used aluminum-based coagulant in water treatment plants.
4. Bleaching powder (Calcium hypochlorite) is a strong oxidizing agent used primarily for disinfection (killing bacteria and viruses) and oxidation, not for coagulation. It does not possess the cationic properties required to destabilize colloidal particles. Therefore, it is not a coagulant.
The pipe appurtenance that releases trapped air in pipelines is:
A)
Check valve
B)
Non-return valve
C)
Sluice valve
D)
Air valve
Step-by-step reasoning:
1. Analysis of the requirement: The question asks for a pipe appurtenance specifically designed to release trapped air from a pipeline. Trapped air can cause 'air locks,' reducing the flow capacity and potentially causing water hammer or pipe bursts.
2. Evaluating Option (d) Air valve: An air valve (or air release valve) is specifically designed to automatically exhaust air that accumulates at high points in a pipeline, ensuring smooth hydraulic flow. This matches the requirement perfectly.
3. Evaluating Option (a) Check valve: A check valve is a one-way valve that allows fluid to flow in one direction and prevents backflow. It does not release air.
4. Evaluating Option (b) Non-return valve: This is another term for a check valve. Its primary function is to prevent reverse flow, not to vent air.
5. Evaluating Option (c) Sluice valve: Also known as a gate valve, it is used to completely stop or allow the flow of water (isolation valve). While it can be used to manually drain a pipe, its primary purpose is not the automatic release of trapped air.
Conclusion: The air valve is the only component listed whose primary function is the removal of trapped air.
Multistage centrifugal pumps are used to obtain:
A)
high discharge
B)
high head
C)
pumping of viscous fluids
D)
high head and high discharge
A centrifugal pump is a kinetic machine that converts rotational energy into pressure head. In a single-stage centrifugal pump, the head (pressure) developed is limited by the impeller diameter and the rotational speed. To achieve a higher head without excessively increasing the impeller size or speed, multiple impellers are arranged in series. In a multistage centrifugal pump, the discharge of the first stage becomes the suction for the second stage, and so on. Consequently, the total head produced is the sum of the heads produced by each individual stage (Total Head = n × Head per stage, where n is the number of stages).
Why other options are incorrect:
- (a) High discharge: To increase discharge (flow rate), one would typically increase the impeller size or use pumps in parallel, not in series (multistage).
- (c) Pumping of viscous fluids: Centrifugal pumps are generally inefficient for highly viscous fluids; positive displacement pumps (like gear or screw pumps) are used for this purpose.
- (d) High head and high discharge: While some large pumps can do both, the specific defining purpose of 'multistaging' is to increase the head. Increasing discharge is handled by the pump's capacity/diameter, not by adding stages.
The main purpose of a soak pit in rural sanitation is to:
A)
Allow percolation of wastewater
B)
Store drinking water
C)
Trap solid waste
D)
Collect rainwater
A soak pit (also known as a seepage pit) is a covered, porous-walled chamber that allows wastewater—typically from a septic tank or greywater sources—to slowly soak into the surrounding soil. The primary mechanism is percolation, where the soil acts as a natural filter to treat the effluent before it reaches the groundwater table.
Why other options are incorrect:
- Option b: Drinking water is stored in tanks or reservoirs, not soak pits, as soak pits are designed for waste disposal.
- Option c: Trapping solid waste is the primary function of a septic tank or a grease trap; a soak pit is designed for liquid effluent. If solids enter a soak pit, they can clog the soil pores (biomat formation), leading to failure.
- Option d: While rainwater harvesting pits exist, a 'soak pit' in the context of rural sanitation specifically refers to the disposal of wastewater.
Which welding process is most commonly used for joining steel water supply pipes on-site?
A)
Arc welding (SMAW)
B)
MIG welding
C)
TIG Welding
D)
Laser welding
Step-by-step reasoning: 1. Analysis of the environment: The question specifies 'on-site' joining of steel water supply pipes. On-site conditions typically involve outdoor environments, wind, dust, and limited access to controlled laboratory settings. 2. Evaluating SMAW (Shielded Metal Arc Welding): SMAW is the most common process for field work because the equipment is portable, it does not require external shielding gas (which would be blown away by wind), and it is highly versatile for various steel thicknesses. 3. Evaluating MIG (Metal Inert Gas) welding: MIG requires a heavy gas cylinder and a regulator to provide shielding gas. This makes it cumbersome for on-site pipework and susceptible to wind interference. 4. Evaluating TIG (Tungsten Inert Gas) welding: TIG is a slow, high-precision process requiring extreme cleanliness and a stable environment. It is generally used in shops for high-pressure or specialized alloy piping, not for general on-site steel water supply pipes. 5. Evaluating Laser welding: This is an industrial, high-cost process requiring massive capital investment and a controlled factory environment; it is not used for field installation of water pipes. Therefore, SMAW is the most practical and commonly used method for on-site steel pipe welding.
Which structure is built for retaining soil?
A)
Septic tank
B)
Soak pit
C)
Infiltration gallery
D)
Retaining wall
Step-by-step reasoning:
1. Analysis of the requirement: The question asks for a structure specifically designed to 'retain soil'. In civil engineering, this refers to resisting the lateral pressure of soil when there is a difference in ground elevation.
2. Evaluating Option (a) Septic tank: A septic tank is a watertight underground container used for the primary treatment of sewage. Its purpose is waste decomposition, not soil retention.
3. Evaluating Option (b) Soak pit: A soak pit is a covered sloping pit that allows effluent to soak into the ground. It is a drainage structure, not a soil-retaining structure.
4. Evaluating Option (c) Infiltration gallery: An infiltration gallery is a horizontal structure used to collect groundwater from a permeable aquifer. It is used for water sourcing, not soil retention.
5. Evaluating Option (d) Retaining wall: A retaining wall is a structure specifically engineered to hold back soil (earth) to prevent slope failure or to create level terraces on sloped terrain. It resists the lateral earth pressure of the soil behind it.
Conclusion: Option (d) is the only structure designed for the purpose of retaining soil.
Which process is used to remove dirt and sand from raw water?
A)
Flocculation
B)
Chlorination
C)
Sedimentation
D)
Aeration
Step-by-step reasoning:
1. The goal is to remove 'dirt and sand' (suspended solids) from raw water. These materials are typically denser than water.
2. Sedimentation is a physical water treatment process that uses gravity to allow heavy particles (like sand, grit, and silt) to settle at the bottom of a tank over a period of time, effectively removing them from the water column.
3. Evaluating other options:
- Flocculation: This is a chemical/mechanical process used to clump small particles together into larger 'flocs' so they can be settled more easily; it does not remove the particles itself but prepares them for sedimentation.
- Chlorination: This is a disinfection process used to kill bacteria and viruses; it does not remove physical dirt or sand.
- Aeration: This is the process of mixing air into water to remove dissolved gases (like CO2 or H2S) or to oxidize dissolved metals (like Iron or Manganese); it is not used for removing sand.
Which one of the following is not a component of water treatment plant:
A)
Rapid sand filter
B)
Flocculator
C)
Transformer
D)
Sedimentation tank
A Water Treatment Plant (WTP) consists of several unit processes designed to remove contaminants from raw water to make it potable.
1. **Rapid Sand Filter (Option a):** This is a core component used for filtration to remove suspended particles and turbidity from water.
2. **Flocculator (Option b):** This is a critical component in the coagulation-flocculation process where chemicals are added and water is gently stirred to form larger 'flocs' of impurities.
3. **Sedimentation Tank (Option d):** This is a unit where water is held still to allow heavy flocs and suspended solids to settle to the bottom by gravity.
**Transformer (Option c):** A transformer is an electrical device used to increase or decrease the voltage of alternating current (AC). While a WTP may use transformers in its electrical substation to power pumps and machinery, a transformer is an electrical engineering component, not a water treatment process component. Therefore, it is not a component of the water treatment process itself.
In a field hydrostatic test, the test pressure is typically:
A)
2.5 times working pressure
B)
1.5 times working pressure
C)
equal to the working pressure
D)
2.0 times working pressure
In pipeline engineering and hydrostatic testing, the primary objective is to ensure the structural integrity of the pipe and the tightness of the joints without causing permanent deformation or failure of the material. According to standard engineering practices (such as ASME B31.3 or various IS codes used in Public Health Engineering), the standard test pressure for a hydrostatic test is typically 1.5 times the Maximum Allowable Working Pressure (MAWP) or the design working pressure.
Step-by-step reasoning:
1. Working Pressure: The pressure at which the system is designed to operate normally.
2. Safety Factor: To ensure the pipe can handle surges or unexpected pressure spikes, it is tested at a higher pressure than the working pressure.
3. Standard Ratio: A factor of 1.5 is the industry standard for hydrostatic testing to verify strength and leak-tightness.
Why other options are incorrect:
- Option (a) 2.5 times: This is excessively high and could lead to plastic deformation or rupture of the pipe walls.
- Option (c) Equal to working pressure: This does not provide a safety margin to ensure the pipe can withstand operational fluctuations.
- Option (d) 2.0 times: While used in some specific high-pressure industrial applications, it is not the 'typical' standard for general PHED pipeline field tests.
The Mizoram Water Supply (Control) Act mainly regulates:
A)
Use and supply of drinking water
B)
Construction of dams
C)
Water quality testing
D)
River water disputes
The Mizoram Water Supply (Control) Act is specifically designed to regulate the distribution, use, and supply of water intended for drinking and domestic purposes within the state. Its primary objective is to ensure that water resources are managed efficiently to provide a steady supply of potable water to the public and to prevent the wastage or unauthorized diversion of such supplies.
Why other options are incorrect:
- Option (b) Construction of dams: This typically falls under larger infrastructure laws, environmental clearances, or the Dam Safety Act.
- Option (c) Water quality testing: While quality is a component of supply, testing is usually governed by the Bureau of Indian Standards (BIS) or the Water (Prevention and Control of Pollution) Act.
- Option (d) River water disputes: These are generally handled at the Central Government level under the Inter-State River Water Disputes Act, 1956, rather than a state-level supply control act.
The process of filling the suction pipe, casing and impeller of a pump with liquid before starting of pump is called-
A)
Water Hammer
B)
Priming
C)
Suction
D)
Cranking
Step-by-step reasoning:
1. **Understanding the Requirement**: Centrifugal pumps are generally not self-priming. If air is present in the suction pipe and casing, the pump cannot create sufficient vacuum to lift the liquid because air is much less dense than water and the impeller cannot generate enough pressure to push the air out and pull the liquid in.
2. **Defining Priming**: Priming is the process of removing air from the suction pipe, pump casing, and impeller by filling them with the liquid to be pumped. This ensures that the impeller is in contact with the liquid, allowing it to create the necessary pressure differential to start the flow.
3. **Evaluating Other Options**:
- **a. Water Hammer**: This is a pressure surge or wave caused when a fluid in motion is forced to stop or change direction suddenly (e.g., closing a valve quickly). It is a destructive phenomenon, not a startup process.
- **c. Suction**: This refers to the act of creating a vacuum to draw fluid into the pump, but it is the result of the pump's operation, not the preparatory process of filling the pump.
- **d. Cranking**: This typically refers to the act of rotating an engine (like an internal combustion engine) to start it, or manually rotating a pump shaft to check for obstructions before startup.
Which one is not a common welding defect?
A)
Slag inclusion
B)
Porosity
C)
Crack
D)
Galvanizing
To identify the correct answer, we must distinguish between welding defects and metallurgical processes.
1. **Slag Inclusion (Option a):** This is a common welding defect where non-metallic solids (slag) are trapped in the weld metal, typically occurring in SMAW (Shielded Metal Arc Welding) if the welder fails to clean between passes.
2. **Porosity (Option b):** This is a common welding defect characterized by small voids or bubbles (gas pockets) trapped in the weld metal, usually caused by contamination or loss of shielding gas.
3. **Crack (Option c):** Cracking is one of the most serious welding defects. It can occur as 'hot cracks' during solidification or 'cold cracks' (hydrogen-induced) after the weld has cooled.
4. **Galvanizing (Option d):** Galvanizing is NOT a defect; it is a protective coating process where steel or iron is coated with a layer of zinc to prevent corrosion. While welding galvanized steel can cause defects (like zinc fumes or porosity), the process of galvanizing itself is a surface treatment, not a welding defect.
Therefore, galvanizing is the only option that is not a welding defect.
Which of the following materials is commonly used in hand pump tube wells?
A)
PVC
B)
GI
C)
RCC
D)
Copper
In the construction of hand pump tube wells, the casing and the rising main (the pipe that carries water from the aquifer to the pump head) must withstand significant mechanical stress, including the weight of the pump assembly, the tension from the pump rod, and the external pressure from the surrounding soil.
1. GI (Galvanized Iron): This is the most common material used for hand pump tube wells because it provides high structural strength, rigidity, and resistance to corrosion due to the zinc coating. It can support the mechanical load of the hand pump mechanism without collapsing or stretching.
2. PVC (Polyvinyl Chloride): While used in some modern shallow wells or as liners, standard PVC lacks the structural rigidity and tensile strength required for the rising main of traditional hand pumps, where the pump cylinder is suspended.
3. RCC (Reinforced Cement Concrete): This is used for large-diameter well linings (open wells) but is physically impossible to use as a tube for a narrow tube well.
4. Copper: While corrosion-resistant, copper is far too expensive and lacks the structural strength required for the depth and pressure of a tube well installation.
Which one of the following is an advantage of GI pipes?
A)
High tensile strength
B)
Prone to rust
C)
Heavy maintenance
D)
Cannot withstand pressure
GI (Galvanized Iron) pipes are made of steel coated with a layer of zinc. Steel inherently possesses high tensile strength, making these pipes durable and capable of supporting significant structural loads and internal pressures.
Analysis of other options:
- Option (b) 'Prone to rust' is incorrect because the primary purpose of galvanization (zinc coating) is to protect the iron from rusting and corrosion.
- Option (c) 'Heavy maintenance' is incorrect because GI pipes are generally low-maintenance compared to non-galvanized steel pipes due to their corrosion resistance.
- Option (d) 'Cannot withstand pressure' is incorrect because GI pipes are specifically used in high-pressure water distribution systems due to their robust material properties.
Aeration in water treatment plant is the process of:
A)
Removing Turbidity
B)
Remove dissolved gases (like CO2, H2S)
C)
Filtration
D)
Disinfection
Aeration is a water treatment process that involves bringing water and air into close contact to facilitate the exchange of gases.
1. Why Option (b) is correct: The primary purpose of aeration is to remove dissolved gases such as carbon dioxide (CO2) and hydrogen sulfide (H2S), which can cause taste, odor, and corrosivity issues. Additionally, aeration introduces oxygen into the water, which helps in the oxidation of dissolved metals like iron (Fe) and manganese (Mn), converting them into insoluble precipitates that can then be filtered out.
2. Why other options are incorrect:
- Option (a) Removing Turbidity: This is typically achieved through coagulation, flocculation, and sedimentation, not aeration.
- Option (c) Filtration: This is a separate physical process used to remove suspended particles and precipitates from water using a porous medium (like sand).
- Option (d) Disinfection: This is the process of killing pathogenic microorganisms, usually achieved through chlorination, UV radiation, or ozonation.
Excessive black smoke from a DG set indicates:
A)
High efficiency
B)
Incomplete fuel combustion
C)
Low oil level
D)
radiator overheating
In a Diesel Generator (DG) set, black smoke is primarily composed of unburnt carbon particles (soot). This occurs when there is an imbalance in the air-fuel ratio—specifically, when there is too much fuel or too little air to ensure complete combustion. Common causes include clogged air filters, faulty fuel injectors, or overloading the engine.
Why other options are incorrect:
- a. High efficiency: High efficiency would result in clear or nearly colorless exhaust, as fuel is being converted to energy optimally.
- c. Low oil level: Low oil levels typically lead to mechanical friction, overheating, or engine seizure, but do not directly cause black smoke (though blue smoke may occur if oil is leaking into the combustion chamber).
- d. Radiator overheating: Overheating usually manifests as white steam or coolant vapor from the radiator or exhaust, not black smoke from the combustion process.
The most economical channel section for open flow is:
A)
Semi-circular
B)
Circular
C)
Rectangular
D)
Trapezoidal
In fluid mechanics, the 'most economical channel section' is defined as the cross-section that provides the maximum discharge for a given cross-sectional area, slope, and roughness. According to Manning's equation, discharge (Q) is maximized when the hydraulic radius (R = Area/Wetted Perimeter) is maximized. This occurs when the wetted perimeter (P) is minimized for a constant area (A). Among all possible geometric shapes, a circle has the smallest perimeter for a given area. For an open channel (where the top is open to the atmosphere), the shape that minimizes the wetted perimeter is a semi-circle.
Comparing the options:
1. Semi-circular: The absolute most economical section because it has the minimum wetted perimeter for a given area.
2. Rectangular: Economical only if the width is twice the depth (b = 2y), but still less efficient than a semi-circle.
3. Trapezoidal: The most economical trapezoidal section is half of a regular hexagon, which is more efficient than a rectangle but less efficient than a semi-circle.
4. Circular: A full circle is used for closed conduits (pipes), not open flow channels.
The specific speed of a Centrifugal pump is given by:
A)
Ns = N Q / H2/3
B)
Ns = N Q / H
C)
Ns = N Q / H3/4
D)
Ns = N Q / H1/3
Option A is correct: Ns = N Q / H2/3.
RCC stands for:
A)
Rolled Cement Concrete
B)
Reinforced Cement Concrete
C)
Ready Cement Concrete
D)
Rapid Cast Cement
RCC stands for Reinforced Cement Concrete. Concrete is a composite material composed of aggregate, cement, and water. While concrete is very strong in compression, it is weak in tension. To overcome this deficiency, steel bars (reinforcement) are embedded into the concrete to carry the tensile loads. This combination of concrete and steel reinforcement is termed 'Reinforced Cement Concrete'.
Analysis of other options:
- 'Rolled Cement Concrete' (a) is not a standard engineering term; 'Roller Compacted Concrete' (RCC) exists but is distinct from the general structural RCC referred to in basic construction materials.
- 'Ready Cement Concrete' (c) is incorrect; the term for pre-mixed concrete is 'Ready-Mix Concrete' (RMC).
- 'Rapid Cast Cement' (d) is not a standard term for RCC.
Electrical Motor converts electrical energy into:
A)
Thermal energy
B)
Potential energy
C)
Mechanical energy
D)
Kinetic energy
An electrical motor is an electromechanical device that converts electrical energy into mechanical energy. It operates on the principle of electromagnetism: when an electric current passes through a coil placed in a magnetic field, it experiences a force (Lorentz force) that creates torque, causing the shaft to rotate.
Analysis of options:
- (a) Thermal energy: While motors generate heat due to resistance (I²R losses), this is an inefficient byproduct, not the intended purpose of the conversion.
- (b) Potential energy: Potential energy is stored energy (like water in a tank); motors produce active motion, not stored potential.
- (c) Mechanical energy: Correct. The rotation of the motor shaft provides the mechanical work used to drive pumps, fans, or machinery.
- (d) Kinetic energy: While the rotating shaft possesses kinetic energy, 'Mechanical energy' is the broader and more accurate technical term for the output of a motor, as it encompasses both the kinetic energy of rotation and the work done on a load.
The process of separating biodegradable and non-biodegradable waste is called:
A)
Disposal
B)
Segregation
C)
Collection
D)
Treatment
Step-by-step reasoning: 1. The question asks for the specific term used for separating waste into different categories (biodegradable vs. non-biodegradable). 2. 'Segregation' is the technical term in Solid Waste Management for the process of dividing waste into different groups (e.g., wet waste, dry waste, hazardous waste) at the source or at a processing plant to facilitate easier recycling and disposal. 3. Analyzing other options: (a) Disposal refers to the final placement of waste (e.g., landfilling); (c) Collection is the act of gathering waste from various points for transport; (d) Treatment involves changing the physical, chemical, or biological character of waste to reduce its volume or toxicity (e.g., composting or incineration). Therefore, segregation is the only term that describes the act of separating.
The term “characterization” in solid waste management refers to:
A)
Identifying components and types of waste
B)
Incinerating solid waste
C)
Burying waste
D)
Burning waste
In Solid Waste Management (SWM), 'characterization' is the process of determining the physical and chemical composition of the waste stream. This involves analyzing the waste to identify the proportions of different components such as organic matter, plastics, paper, glass, metals, and hazardous materials. This step is critical for designing efficient waste collection, sorting, and disposal systems (e.g., deciding whether to use composting, recycling, or incineration).
Why other options are incorrect:
- Option b (Incinerating solid waste) refers to 'Incineration', a thermal treatment process.
- Option c (Burying waste) refers to 'Landfilling'.
- Option d (Burning waste) is a general term for combustion or open burning, which is a method of disposal, not characterization.
Before starting a DG set, which of the following should be checked first?
A)
Coolant level
B)
Oil level
C)
Fuel level
D)
All of the above
Before starting a Diesel Generator (DG) set, a comprehensive pre-start check is mandatory to ensure the safety of the equipment and to prevent catastrophic engine failure.
1. **Oil Level (Lube Oil):** Lubrication is critical for reducing friction between moving parts. Starting an engine with low oil can lead to immediate seizure or severe wear of the cylinder walls and bearings.
2. **Coolant Level:** The cooling system prevents the engine from overheating. Insufficient coolant can lead to thermal expansion, warped cylinder heads, or engine overheating shortly after startup.
3. **Fuel Level:** Ensuring there is sufficient fuel prevents the engine from stalling mid-operation or sucking air/sediments from the bottom of the tank into the fuel system, which would require priming the system.
Since all three parameters are critical 'pre-flight' checks for any internal combustion engine, the correct answer is 'All of the above'.
Assam-type buildings are primarily made of:
A)
Stone and RCC
B)
Timber and corrugated roofing
C)
GI sheets
D)
Glass and steel
Assam-type buildings are a traditional style of architecture developed in the Northeast region of India (specifically Assam and surrounding areas) to withstand high seismic activity (earthquakes) and heavy rainfall. The key characteristics include: 1. Lightweight structure: They primarily use timber for the framework and walls (often using 'Ikra' or reed walls plastered with mud) to ensure the building is light and flexible during tremors. 2. Sloping Roofs: Due to heavy monsoon rains, they feature steeply pitched roofs made of corrugated galvanized iron (CGI) sheets to ensure quick drainage of water.
Analysis of other options:
- Option (a) Stone and RCC: These are heavy materials that are more susceptible to collapse during high-magnitude earthquakes if not engineered specifically, and they do not define the 'Assam-type' vernacular style.
- Option (c) GI sheets: While GI sheets are used for the roof, they are not the primary material for the entire building structure (which requires timber for the frame).
- Option (d) Glass and steel: These are modern industrial materials and are not characteristic of traditional Assam-type residential construction.