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Past Questions
Cavitation in a pump mainly occurs due to:
A)
high discharge
B)
low suction pressure
C)
high motor speed
D)
excess lubrication
Cavitation is a phenomenon that occurs in centrifugal pumps when the local pressure of the liquid drops below its vapor pressure at the operating temperature. This causes the liquid to boil and form vapor bubbles (cavities). When these bubbles move to regions of higher pressure (like the impeller eye or vanes), they collapse violently, creating shockwaves that erode the metal surface.
Step-by-step reasoning:
1. The pressure at the suction side of the pump must be maintained above the vapor pressure of the liquid to prevent boiling.
2. If the suction pressure becomes too low (due to high suction lift, clogged intake, or high fluid temperature), the pressure drops below the vapor pressure.
3. This leads to the formation of vapor bubbles, which is the definition of cavitation.
Analysis of other options:
- (a) High discharge: While high flow rates can increase friction losses in the suction line (which indirectly lowers pressure), high discharge itself is not the primary cause; the pressure drop is the cause.
- (c) High motor speed: Increasing speed increases the Net Positive Suction Head Required (NPSHr), which can make a pump more prone to cavitation, but the physical cause is still the resulting low pressure relative to vapor pressure.
- (d) Excess lubrication: Lubrication pertains to the bearings and seals, not the hydraulic fluid path, and has no effect on cavitation.
Storm water drains are designed to carry:
A)
Rainwater runoff
B)
Sewage
C)
Industrial effluent
D)
Sludge
Storm water drains are specifically designed to collect and convey rainwater runoff from roofs, roads, and open surfaces during rainfall. They are not meant for wastewater transport. Sewage is carried by sanitary sewers, industrial effluent by separate industrial/wastewater systems, and sludge is a concentrated solid-liquid waste handled in treatment plants, not storm drains.
The most suitable pump for deep bore wells is:
A)
Centrifugal pump
B)
Reciprocating pump
C)
Submersible pump
D)
Air lift pump
Step-by-step reasoning:
1. **Understanding Deep Bore Wells**: Deep bore wells involve lifting water from significant depths (often exceeding 20-30 meters).
2. **The Suction Limit**: Standard surface-mounted pumps (like centrifugal pumps) rely on suction. Due to atmospheric pressure, the theoretical maximum suction lift is about 10.3 meters, and in practice, it is limited to 6-8 meters. Therefore, they cannot lift water from deep bore wells.
3. **Submersible Pump Mechanism**: A submersible pump is designed to be fully immersed in the water. Instead of 'pulling' water up via suction, it 'pushes' the water upward using a multi-stage centrifugal impeller. This eliminates the suction lift limitation, making it the most efficient and suitable choice for deep wells.
4. **Evaluating Other Options**:
- **Centrifugal pump (a)**: Generally surface-mounted; limited by suction lift.
- **Reciprocating pump (b)**: While they can handle higher heads, they are bulky, have high maintenance due to valves, and are not practical for installation inside narrow bore wells.
- **Air lift pump (d)**: These use compressed air to lift water. While they can work in deep wells, they have very low efficiency and require a constant supply of high-pressure air, making them less suitable than submersible pumps for general engineering applications.
PVC stands for:
A)
Poly Vinyl Cement
B)
Plastic Vinyl Cement
C)
Poly Variable Chloride
D)
Poly Vinyl Chloride
PVC stands for Poly Vinyl Chloride, a common thermoplastic polymer used in pipes, insulation, and fittings. Option d is correct because it matches the standard expansion of PVC. The other options are incorrect: (a) Poly Vinyl Cement is not a valid term, (b) Plastic Vinyl Cement is incorrect and not the standard abbreviation, and (c) Poly Variable Chloride is meaningless in this context.
Segregation of solid waste means:
A)
Burning waste
B)
Separating waste at source
C)
Dumping waste
D)
Compacting waste
Segregation of solid waste is the process of dividing waste into different categories (such as biodegradable, non-biodegradable, recyclable, and hazardous) at the point where it is generated (the source). This is a critical step in Integrated Solid Waste Management (ISWM) because it prevents contamination of recyclables and organic waste, making subsequent treatment and disposal processes more efficient.
Why other options are incorrect:
- Option (a) Burning waste: This is known as incineration, which is a method of waste disposal/volume reduction, not segregation.
- Option (c) Dumping waste: This refers to landfilling or open dumping, which is the final disposal stage.
- Option (d) Compacting waste: This is a mechanical process used to reduce the volume of waste for easier transport or storage, not a method of separation.
Rainwater harvesting primarily aims to:
A)
Increase wastewater generation
B)
Conserve water resources
C)
Increase runoff
D)
Reduce evaporation
Rainwater harvesting (RWH) is the process of collecting, filtering, and storing rainwater from surfaces (like rooftops or open grounds) for future use or for recharging groundwater aquifers.
1. Why Option (b) is correct: The primary objective of RWH is to reduce reliance on groundwater and municipal supplies, prevent the waste of rainwater, and ensure a sustainable water supply, thereby conserving water resources.
2. Why Option (a) is incorrect: RWH aims to provide a clean water source; it does not intend to increase the generation of wastewater.
3. Why Option (c) is incorrect: RWH actually aims to *decrease* surface runoff. By capturing rain where it falls, it prevents water from flowing away rapidly into drains, which also helps in reducing urban flooding and soil erosion.
4. Why Option (d) is incorrect: While storing water in closed tanks may reduce evaporation compared to open reservoirs, the primary 'aim' of the entire harvesting system is conservation and resource management, not specifically the reduction of the evaporation process itself.
Which of the following is a lower pair?
A)
Cam and Follower
B)
Shaft rotating in a bearing
C)
Gear teeth connection
D)
Belt and pulley
In the Theory of Machines, kinematic pairs are classified based on the type of contact between the two mating elements:
1. **Lower Pair**: A pair is called a lower pair when the two mating elements have surface contact. Examples include sliding pairs, turning pairs, and screw pairs.
2. **Higher Pair**: A pair is called a higher pair when the two mating elements have point or line contact.
Analysis of the options:
- **a. Cam and Follower**: The contact between the cam profile and the follower is typically a point or a line. Therefore, it is a **Higher Pair**.
- **b. Shaft rotating in a bearing**: The shaft and the bearing surface maintain surface contact throughout the rotation (Turning Pair). Therefore, it is a **Lower Pair**.
- **c. Gear teeth connection**: The contact between two mating gear teeth occurs along a line. Therefore, it is a **Higher Pair**.
- **d. Belt and pulley**: The contact between the belt and the pulley is a line contact. Therefore, it is a **Higher Pair**.
Thus, the only lower pair among the given options is the shaft rotating in a bearing.
Which item is measured in cubic metres?
A)
Earthwork excavation
B)
Brick masonry
C)
Plastering
D)
Painting
In civil engineering estimation and costing, items are measured based on their dimensions.
1. Earthwork excavation (Option a): This involves removing a volume of soil (Length × Width × Depth), therefore it is measured in cubic metres (m³).
2. Brick masonry (Option b): While brick masonry is typically measured in cubic metres (m³), in many standardized competitive exams for Junior Engineers, if 'Earthwork' is listed, it is the primary example of volume-based measurement. However, technically, both (a) and (b) are measured in m³. In the context of standard multiple-choice questions for this specific syllabus, Earthwork is the most fundamental volume item. (Note: If the masonry is a thin partition wall, it is measured in square metres, but general masonry is m³).
3. Plastering (Option c): This is a surface treatment with a constant thickness, measured in square metres (m²).
4. Painting (Option d): This is a surface finish, measured in square metres (m²).
Comparing the options, Earthwork excavation is universally measured in cubic metres regardless of the scale, making it the most definitive answer.
CI pipe stands for:
A)
Cement Iron
B)
Circular Iron
C)
Cast Iron
D)
Common Iron
In the context of piping materials and civil/mechanical engineering, 'CI' is the standard abbreviation for Cast Iron. Cast iron pipes are widely used in water distribution and sewage systems due to their high compressive strength and durability.
- Option (a) 'Cement Iron' is incorrect; while cement-lined cast iron pipes exist, the material itself is not called 'Cement Iron'.
- Option (b) 'Circular Iron' is incorrect; while pipes are circular, this is not a material classification.
- Option (d) 'Common Iron' is incorrect; this is not a technical term used in engineering material specifications.
Which method of population forecasting assumes uniform growth rate?
A)
Logistic curve method
B)
Arithmetic increase method
C)
Geometric increase method
D)
Incremental increase method
In water supply planning, population forecasting methods are used to estimate future water demand.
1. **Arithmetic Increase Method (Correct):** This method assumes that the population increases by a constant amount (a uniform growth rate in absolute terms) each decade. The formula is Pn = P0 + n*d, where 'd' is the average increase per decade. It is typically used for old, established cities where growth has stabilized.
2. **Geometric Increase Method:** This method assumes that the percentage growth rate remains constant, meaning the population grows exponentially. It is suitable for rapidly growing young cities.
3. **Incremental Increase Method:** This is a combination of the arithmetic and geometric methods. It accounts for the average increase as well as the incremental increase in that growth rate.
4. **Logistic Curve Method:** This method assumes that the population growth follows an S-shaped curve, starting slowly, accelerating, and then leveling off as it reaches a saturation limit (carrying capacity).
GI pipe stands for:
A)
Galvanized Iron
B)
Ground Iron
C)
General Iron
D)
Grey Iron
GI pipe stands for Galvanized Iron pipe. Galvanization is the process of applying a protective zinc coating to iron or steel to prevent rusting and corrosion. This is achieved by immersing the iron pipe in a bath of molten zinc.
Analysis of options:
- Option (a) Galvanized Iron: Correct. This is the standard industry term for iron pipes coated with zinc.
- Option (b) Ground Iron: Incorrect. This is not a standard term for piping materials.
- Option (c) General Iron: Incorrect. While iron is a general material, 'General Iron' is not a specific technical classification for pipes.
- Option (d) Grey Iron: Incorrect. Grey iron (or Cast Iron) is a type of iron based on carbon content, but 'GI' specifically refers to the galvanization process, not the internal metallurgy of the iron.
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
A hydrostatic test is a pressure test used to verify the structural integrity and leak-tightness of a piping system. According to standard engineering practices and most international codes (such as ASME B31.3 for process piping), the standard test pressure for a hydrostatic test is typically 1.5 times the design pressure or the maximum allowable working pressure (MAWP).
Step-by-step reasoning:
1. Working Pressure: This is the pressure at which the system is designed to operate normally.
2. Safety Margin: To ensure the system can handle surges and to identify potential weak points or leaks, it must be tested at a pressure higher than the working pressure.
3. Standard Factor: A factor of 1.5 is widely accepted as the industry standard to provide a sufficient safety margin without risking the permanent deformation or rupture of the pipe walls.
Analysis of other options:
- Option (a) 2.5 times: This is generally too high and could lead to plastic deformation or failure of the piping system.
- Option (c) Equal to working pressure: This would only prove the system works under normal conditions; it would not provide a safety margin to ensure integrity against pressure spikes.
- Option (d) 2.0 times: While some specific high-pressure codes might use higher factors, 1.5 is the general 'typical' standard for field hydrostatic tests.
Which parameter is not considered in the design of pumping mains?
A)
Turbidity
B)
Flow rate
C)
Efficiency
D)
Head
The design of pumping mains (the pipelines used to transport fluid from a pump to its destination) focuses on hydraulic parameters to ensure the system operates efficiently and safely.
1. **Flow rate (b):** This is a primary design parameter. The diameter of the pipe is selected based on the required flow rate to maintain an optimal velocity, preventing both sedimentation (if too slow) and excessive friction losses or water hammer (if too fast).
2. **Head (d):** The total dynamic head (TDH), which includes static lift and friction losses, is critical for selecting the pump capacity and determining the pressure rating (class) of the pipes used in the main.
3. **Efficiency (c):** System efficiency (including pump efficiency and minimizing frictional head loss) is essential for calculating power requirements and operational costs.
**Turbidity (a)** refers to the cloudiness or haziness of a fluid caused by individual particles. While turbidity is a critical parameter for water *treatment* and *quality* analysis, it does not influence the hydraulic design, pipe sizing, or pressure calculations of the pumping mains themselves.
In a CI engine, ignition of fuel takes place due to:
A)
spark plug
B)
Carburettor
C)
high temperature of compressed air
D)
glow plug
In a CI (Compression Ignition) engine, air is compressed to a very high pressure, which raises its temperature sufficiently to ignite the injected fuel spontaneously. Therefore, ignition occurs due to the high temperature of compressed air. The other options are incorrect: a spark plug is used in SI (spark ignition) engines, a glow plug is only an auxiliary starting aid in some diesel engines and is not the primary cause of ignition, and a carburettor is used to mix air and fuel in SI engines, not for ignition in CI engines.
What is the main purpose of maintaining a logbook in a Water Supply System?
A)
To record personal attendance
B)
To track daily weather report
C)
To record operational data and performance of system
D)
Sedimentation tank
In Water Supply Management, a logbook serves as the primary official record for the operation and maintenance (O&M) of the system. Its main purpose is to document critical operational data such as pump running hours, flow rates, pressure readings, chemical dosage (e.g., chlorine), water levels in reservoirs, and any breakdowns or repairs. This data is essential for analyzing system performance, predicting maintenance needs, and ensuring accountability.
Analysis of other options:
- Option (a) 'To record personal attendance' is the purpose of an attendance register, not a system logbook.
- Option (b) 'To track daily weather report' may be a secondary observation in some contexts, but it is not the 'main purpose' of a water supply operational logbook.
- Option (d) 'Sedimentation tank' is a physical component of a water treatment plant, not a purpose for maintaining a record book.
For a given real power and voltage, if power factor decreases, the line current:
A)
Decreases
B)
Increases
C)
Remains same
D)
Becomes zero
For a single-phase AC load, real power P = VI cosφ, where cosφ is the power factor. For a given real power P and voltage V, line current I = P / (V × power factor). So if power factor decreases, the denominator becomes smaller and the current must increase. Hence, the correct answer is (b) Increases.
The resistivity of a semiconductor compared to a conductor at room temperature is:
A)
Slightly lower
B)
Zero
C)
Higher
D)
Much lower
A semiconductor has far fewer free charge carriers than a conductor at room temperature, so it offers more resistance to current flow. Therefore, its resistivity is much higher than that of a conductor. Option (b) is wrong because resistivity is not zero, and (a) and (d) are incorrect because conductors have much lower resistivity than semiconductors.
Given that MVA denotes Mega Volt-Ampere, MW denotes Mega Watt, and cos φ is the power factor, which of the following relations is correct?
A)
MVA = MW × cos φ
B)
MW = MVA × cos φ
C)
cos φ = MVA / MW
D)
cos φ = MW × MVA
In AC circuits, real power (MW) = apparent power (MVA) × power factor (cos φ). Since MVA is the apparent power and MW is the active/real power, multiplying MVA by cos φ gives MW. Therefore, option (b) is correct. Option (a) is incorrect because MVA is not obtained by multiplying MW by cos φ; rather, MVA = MW / cos φ. Option (c) is incorrect because cos φ = MW / MVA, not MVA / MW. Option (d) has no correct physical meaning.
A pump motor trips immediately after starting. Which instrument helps verify if starting current is abnormally high?
A)
Voltmeter
B)
Clamp Meter
C)
Megger
D)
Frequency Meter
A clamp meter is used to measure current directly in a live circuit without disconnecting the conductor. If a pump motor trips immediately after starting, checking the starting current with a clamp meter helps determine whether the current is abnormally high. A voltmeter measures voltage, a megger checks insulation resistance, and a frequency meter measures frequency, so they are not suitable for verifying starting current.
The purpose of chlorination is:
A)
Disinfection
B)
Softening
C)
Sedimentation
D)
Aeration
Chlorination is the process of adding chlorine to water mainly to destroy disease-causing microorganisms, so its primary purpose is disinfection. It does not soften water, remove suspended particles by sedimentation, or add oxygen by aeration.
Power factor of an AC circuit is defined as the ratio of:
A)
Active power to apparent power
B)
Reactive power to apparent power
C)
Apparent power to active power
D)
Reactive power to active power
Option A is correct: Active power to apparent power.
The primary objective of preventive maintenance in electrical Operation and Maintenance is to:
A)
Minimize failures
B)
Reduce capital cost
C)
Increase energy use
D)
Raise operating temperature
Preventive maintenance is done before a breakdown occurs, with the main aim of detecting and correcting faults early so that equipment remains reliable and unexpected failures are reduced. It is not primarily meant to reduce capital cost, increase energy use, or raise operating temperature. Therefore, the correct answer is 'Minimize failures'.
Which of the following materials is most commonly used for overhead transmission line conductors due to its good conductivity and low cost?
A)
Copper
B)
Aluminium
C)
Silver
D)
Tungsten
Aluminium is most commonly used for overhead transmission line conductors because it offers a good balance of electrical conductivity, low weight, and low cost. Copper has higher conductivity but is heavier and more expensive, so it is less preferred for overhead lines. Silver is too costly, and tungsten is not used for this purpose due to poor suitability and high cost.
CI pipe stands for:
A)
Cement Iron
B)
Circular Iron
C)
Cast Iron
D)
Common Iron
CI in piping materials stands for Cast Iron. It is a common pipe material used in water supply and drainage works. The other options are not standard engineering terms for CI pipe.
Twin pit latrine is commonly adopted in:
A)
Airports
B)
Industries
C)
Rural sanitation
D)
Hotels
Twin pit latrines are a low-cost, on-site sanitation system mainly promoted for rural areas. They are suitable where sewerage is not available and can safely decompose excreta in alternating pits. Airports, industries, and hotels generally require more advanced or high-capacity sanitation systems, so they are not the common setting for twin pit latrines.