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Past Questions — 2025
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 of the following pipe materials is corrosion-resistant?
A)
DI
B)
CI
C)
HDPE
D)
ERW
To determine which material is corrosion-resistant, we must analyze the chemical properties of each option:
1. **DI (Ductile Iron):** While stronger and more flexible than cast iron, DI is still a metallic material prone to oxidation and corrosion when exposed to moisture and soil chemicals. It usually requires internal linings (like cement mortar) and external coatings (like zinc or bitumen) to resist corrosion.
2. **CI (Cast Iron):** Like DI, cast iron is a ferrous metal. It is highly susceptible to corrosion (rusting) and tuberculation over time, especially in acidic or salty environments.
3. **HDPE (High-Density Polyethylene):** This is a thermoplastic polymer. Plastics are non-conductive and chemically inert to most acids, bases, and salts. Because it does not oxidize or rust, HDPE is inherently corrosion-resistant and is widely used in corrosive soil conditions or for transporting chemicals.
4. **ERW (Electric Resistance Welded Steel):** ERW refers to the manufacturing process of steel pipes. Steel is highly susceptible to corrosion and requires extensive galvanization or coating to prevent rust.
Conclusion: HDPE is the only non-metallic material listed, making it the only inherently corrosion-resistant option.
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.
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.
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 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 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.
The discharge of water flowing through a circular pipe of 100 mm diameter, having a velocity of 1.0 m/s is :
A)
28.26 m3/hr
B)
30.50 m3/hr
C)
25.62 m3/hr
D)
38.26 m3/hr
Step-by-step calculation:
1. **Identify Given Data**:
- Diameter of the pipe (d) = 100 mm = 0.1 m
- Velocity of flow (v) = 1.0 m/s
2. **Calculate Cross-sectional Area (A)**:
The area of a circular pipe is given by the formula: A = (π/4) * d²
A = (3.14159 / 4) * (0.1)²
A = 0.7854 * 0.01 = 0.007854 m²
3. **Calculate Discharge (Q) in m³/s**:
Discharge is the product of area and velocity: Q = A * v
Q = 0.007854 m² * 1.0 m/s = 0.007854 m³/s
4. **Convert Discharge to m³/hr**:
Since there are 3600 seconds in one hour:
Q (m³/hr) = Q (m³/s) * 3600
Q = 0.007854 * 3600 = 28.2744 m³/hr
Rounding to two decimal places, we get 28.27 m³/hr, which most closely matches option (a) 28.26 m³/hr (the slight difference is due to the precision of π used in the question's source calculation, likely using π ≈ 3.14).
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.
A pump set draws more current than rated during operation. The most likely electrical cause is
A)
High voltage supply
B)
Proper earthing
C)
Motor overloading
D)
Low winding temperature
Step-by-step reasoning:
1. Understanding Current Draw: In an electric motor, the current drawn is directly proportional to the mechanical load (torque) applied to the shaft.
2. Analyzing Motor Overloading: When a pump set is overloaded (e.g., due to a jammed impeller, high fluid viscosity, or pumping beyond rated capacity), the motor must produce more torque to maintain its speed. To produce this additional torque, the motor draws more current from the power supply, often exceeding its rated current (Full Load Amps).
3. Evaluating other options:
- (a) High voltage supply: Generally, an increase in voltage does not lead to a significant increase in current for an induction motor at a constant load; in some cases, it may slightly decrease current or cause saturation, but it is not the 'most likely' cause of overcurrent compared to overloading.
- (b) Proper earthing: Earthing is a safety mechanism to prevent electric shock and does not affect the operational current draw of the motor under normal conditions.
- (d) Low winding temperature: Lower temperatures typically result in lower resistance in the windings. While this might slightly affect current, it would not cause a motor to draw 'more than rated' current during operation; in fact, overheating is usually a result of high current, not the cause of it.
What is the main purpose of using a starter for motors in a pumping station?
A)
To reduce water flow
B)
To cool the motor
C)
To limit starting current
D)
To increase voltage
When an electric motor (especially an induction motor used in pumping stations) is started directly from the mains, it draws a very high initial current, often 5 to 7 times its rated full-load current. This is because the motor starts from a standstill (zero speed), meaning there is no back-EMF to oppose the supply voltage. This high 'inrush current' can cause voltage dips in the power system, damage the motor windings due to overheating, and put excessive mechanical stress on the pump couplings. A motor starter (such as a Star-Delta starter or an Auto-transformer starter) is used to reduce the starting voltage applied to the motor, thereby limiting the starting current to a safe level.
Analysis of other options:
- (a) To reduce water flow: Water flow is controlled by valves or Variable Frequency Drives (VFDs), not by the starter.
- (b) To cool the motor: Cooling is handled by fans or cooling jackets; starters do not provide cooling.
- (d) To increase voltage: Starters are designed to either maintain or temporarily reduce voltage to protect the motor; they are not used to increase voltage.
What should be checked regularly to maintain lead-acid batteries in good condition?
A)
Cable colour
B)
Charger fan speed
C)
Size of terminals
D)
Electrolyte level
Lead-acid batteries contain an electrolyte consisting of sulfuric acid and water. During the charging and discharging process, water can be lost due to evaporation or electrolysis (gassing), especially in vented batteries. If the electrolyte level drops and the lead plates are exposed to air, it can lead to permanent damage (sulfation) and a decrease in battery capacity. Therefore, checking and topping up the electrolyte level with distilled water is a critical part of regular maintenance.
Why other options are incorrect:
- a. Cable colour: The colour of the cables is for identification (e.g., red for positive, black for negative) and does not affect the chemical or electrical health of the battery.
- b. Charger fan speed: While charger cooling is important for the charger's longevity, it is not a maintenance check for the battery itself.
- c. Size of terminals: Terminal size is a fixed physical characteristic determined during manufacturing and does not change or require regular checking for maintenance.
The process of separating biodegradable and non-biodegradable waste is called:
A)
Disposal
B)
Segregation
C)
Collection
D)
Treatment
The process of separating waste into different categories—such as biodegradable (organic) and non-biodegradable (plastics, metals, glass)—at the source or at a processing facility is known as 'Segregation'. This is a critical step in waste management as it allows for efficient recycling and composting.
Why other options are incorrect:
- a. Disposal: This is the final stage of waste management where waste is placed in a landfill or incinerated.
- c. Collection: This refers to the gathering of waste from various points and transporting it to a transfer station or disposal site.
- d. Treatment: This involves the physical, chemical, or biological processing of waste to reduce its toxicity or volume (e.g., composting or anaerobic digestion) after it has been segregated.
The key reason for conducting a water supply survey is to:
A)
Increase groundwater level
B)
Assess rainfall patterns
C)
Improve road network
D)
Plan intake and reservoir location
A water supply survey is a comprehensive preliminary investigation conducted to gather data necessary for the design and implementation of a water supply system. The primary objectives of such a survey include determining the current and future water demand, identifying available water sources, and analyzing the topography of the area. This data is critical for the strategic planning of infrastructure, specifically the location of the intake (where water is drawn from the source) and the reservoir/service reservoirs (where water is stored for distribution), to ensure gravity flow where possible and minimize pumping costs.
Why other options are incorrect:
- Option (a): Increasing groundwater levels is a result of rainwater harvesting or groundwater recharge projects, not a reason for conducting a survey.
- Option (b): While rainfall patterns are studied during a survey to estimate water yield, the 'key reason' for the overall survey is the planning of the supply system, not just assessing rainfall.
- Option (c): Improving road networks is the domain of transportation or civil infrastructure engineering, not water supply engineering.
Which structure is built for retaining soil?
A)
Septic tank
B)
Soak pit
C)
Infiltration gallery
D)
Retaining wall
A retaining wall is a structure specifically designed to resist the lateral pressure of soil, preventing it from sliding or collapsing. It is commonly used in areas where there is a steep change in ground elevation, such as along roadsides, basements, or bridge abutments.
Analysis of other options:
- a. Septic tank: A watertight container used for the primary treatment of sewage.
- b. Soak pit: A covered pit that allows wastewater to slowly soak into the ground.
- c. Infiltration gallery: A horizontal structure used to collect groundwater from a sandy or gravelly aquifer.
Therefore, only the retaining wall is built for the purpose of retaining soil.
Which material is commonly used for conductors in machine windings?
A)
Rubber
B)
Copper
C)
Lead
D)
Brass
In electrical machines (such as motors, generators, and transformers), the windings require a material with high electrical conductivity to minimize power loss due to heating (I²R losses) and to maximize efficiency.
1. **Copper (Option b):** It is the most commonly used material for windings because it has one of the highest electrical conductivity values among all metals (second only to silver, which is too expensive for industrial use). It also possesses good ductility and thermal conductivity.
2. **Rubber (Option a):** Rubber is an insulator, not a conductor. It is used for insulation of wires, not for the conductor itself.
3. **Lead (Option c):** Lead has very poor electrical conductivity compared to copper and is too soft and heavy for use in machine windings.
4. **Brass (Option d):** Brass is an alloy of copper and zinc. While it is conductive, its conductivity is significantly lower than that of pure copper, leading to higher energy losses.
Which instrument is commonly used to test insulation resistance of an induction motor?
A)
Ammeter
B)
Megger
C)
Voltmeter
D)
Multimeter
Insulation resistance testing requires the application of a high DC voltage (typically 500V or 1000V) to the winding to check for leakage current or breakdown in the insulation. A Megger (short for Mega-ohmmeter) is specifically designed for this purpose; it generates a high voltage and measures the resulting very high resistance (in Mega-ohms).
Why other options are incorrect:
- a. Ammeter: Measures electric current flowing through a circuit, not resistance.
- c. Voltmeter: Measures the potential difference between two points, not resistance.
- d. Multimeter: While a multimeter can measure low resistance (continuity), it uses a low-voltage battery that is insufficient to stress the insulation of a motor winding to detect potential failures or leakage.