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Past Questions — 2026
The main purpose of a service reservoir is:
A)
Water treatment
B)
Storage and distribution
C)
Pumping
D)
Filtration
A service reservoir in a water supply system is primarily used to store treated water and supply it to the distribution network as demand varies throughout the day. It helps balance hourly demand fluctuations and maintain pressure.
Why others are incorrect:
(a) Water treatment — this is done in treatment plants, not in service reservoirs.
(c) Pumping — pumping is done by pumps and pumping stations.
(d) Filtration — filtration is a treatment process, not the function of a service reservoir.
The economically most efficient rectangular channel section has:
A)
b = y
B)
b = 2y
C)
b = 3y
D)
b = 4y
For the most economical rectangular channel section, the hydraulic radius is maximized for a given area. For a rectangular section, this condition gives breadth b = 2y, where y is the depth of flow. Hence option (b) is correct. The other options do not satisfy the condition for minimum wetted perimeter for a given flow area.
A soak pit is used for:
A)
Disposal of septic tank effluent
B)
Water storage
C)
Pumping water
D)
Chlorination
A soak pit is a simple underground pit used to absorb and percolate liquid waste, especially the effluent discharged from a septic tank, into the surrounding soil. It helps in safe disposal by infiltration. Water storage is done in tanks, pumping requires pumps, and chlorination is a disinfection process, not a function of a soak pit.
In an overhead transmission line system, a ground wire (earth wire) is installed above phase conductors. What is the primary purpose of providing this ground wire?
A)
To carry load current through an additional conductor during normal system operation
B)
To reduce the overall electrical resistance of the transmission line conductors
C)
To protect the transmission line against lightning surges by diverting them to earth
D)
To improve voltage regulation of the line by minimizing voltage drop along the route
The ground wire (earth wire) is placed above the phase conductors mainly to act as a shielding conductor. It intercepts lightning strokes and provides a low-resistance path to earth, thereby protecting the line insulation and equipment from overvoltage damage. Option (a) is incorrect because the earth wire does not carry normal load current. Option (b) is incorrect because it is not meant to reduce conductor resistance. Option (d) is incorrect because voltage regulation is not its primary function.
Frequent tripping of a circuit breaker due to protection operation under normal load indicates:
A)
Correct protection operation
B)
High insulation resistance
C)
Incorrect relay settings
D)
Good power factor
If a circuit breaker trips frequently even under normal load, it usually means the protection device is too sensitive or wrongly set. This points to incorrect relay settings, because the relay is operating when it should not.
(a) Correct protection operation is not the best answer, because normal load should not cause repeated tripping.
(b) High insulation resistance is generally a good condition and would not cause unwanted tripping.
(d) Good power factor also does not directly explain frequent tripping.
Therefore, the correct answer is incorrect relay settings.
PVC stands for:
A)
Poly Vinyl Cement
B)
Plastic Vinyl Cement
C)
Poly Variable Chloride
D)
Poly Vinyl Chloride
PVC is the common abbreviation for Poly Vinyl Chloride, a widely used thermoplastic material in piping and construction. The other options are incorrect because PVC does not stand for cement, plastic vinyl cement, or variable chloride.
Soft starters control motor starting by varying:
A)
Supply voltage
B)
Supply frequency
C)
Rotor circuit resistance
D)
Phase sequence of supply
Soft starters reduce the starting current and mechanical stress of a motor by gradually increasing the applied supply voltage from a low value to full voltage. They do not vary frequency, rotor resistance, or phase sequence. Frequency variation is done by a VFD, rotor resistance is used in slip-ring motors, and phase sequence only affects rotation direction.
In a pump house, which of the following components must be effectively earthed to ensure electrical safety?
A)
Motor terminals
B)
Motor windings
C)
Motor body
D)
Motor bearings
For electrical safety, the exposed metal parts of equipment that can become live due to insulation failure must be effectively earthed. In a pump house, the motor body is the part that should be earthed to prevent electric shock. Motor terminals and windings are live electrical parts and are not earthed directly, while motor bearings are mechanical parts and not the primary earthing point.
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.
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.
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.
In a 33 kV sub-station, which instrument is used to step down high voltage to a safe and measurable level for metering and protection purposes?
A)
Power transformer
B)
Potential transformer
C)
Current transformer
D)
Lightning arrester
A potential transformer (PT), also called a voltage transformer, is used in a 33 kV sub-station to step down high voltage to a low, safe, and standardized value for metering and protection circuits. A current transformer (CT) is used for stepping down current, not voltage. A power transformer is used for transmitting power between voltage levels, and a lightning arrester protects equipment from surges, not for metering.
The Mizoram Water Supply (Control) Act mainly regulates:
A)
Road construction
B)
Forest management
C)
Electricity supply
D)
Water supply and distribution
The Mizoram Water Supply (Control) Act is concerned with the regulation, control, and management of water supply systems, including distribution. It does not deal with roads, forests, or electricity. Therefore, the correct option is (d) Water supply and distribution.
Tree branches coming into contact with a 33 kV overhead line can result in:
A)
Improved insulation
B)
Reduced line impedance
C)
Flashover and faults
D)
Higher tensile strength
When tree branches touch or come very close to a 33 kV overhead line, the insulation between the conductor and the tree is disturbed. This can cause arcing or flashover, leading to line faults and possible outages. The other options are incorrect: tree contact does not improve insulation, reduce line impedance, or increase tensile strength of the line.
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 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.
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.
If a three-phase induction motor in a pump house is found to rotate in the wrong direction during trial run, what should be done to correct the direction of rotation?
A)
Change starter
B)
Interchange any two phases
C)
Increase voltage
D)
Replace motor
In a three-phase induction motor, the direction of rotation depends on the phase sequence of the supply. If the motor rotates in the wrong direction, reversing the phase sequence reverses the rotation. This is done by interchanging any two of the three supply phases. Changing the starter, increasing voltage, or replacing the motor will not correct the direction of rotation.
RCC stands for:
A)
Reinforced Clay Concrete
B)
Ready Cement Concrete
C)
Reinforced Concrete Column
D)
Reinforced Cement Concrete
RCC is the standard abbreviation for Reinforced Cement Concrete, a composite material in which steel reinforcement is embedded in concrete to improve tensile strength. The other options are incorrect because RCC does not mean Reinforced Clay Concrete, Ready Cement Concrete, or Reinforced Concrete Column.
HDPE pipes are preferred because they are:
A)
Corrosion resistant
B)
Brittle
C)
Heavy
D)
Expensive
HDPE (High-Density Polyethylene) pipes are widely preferred in water supply and piping systems because they do not corrode like metal pipes. They are also lightweight, flexible, and durable. The other options are incorrect: HDPE pipes are not brittle, not heavy, and are generally cost-effective rather than expensive.
Rainwater harvesting primarily aims to:
A)
Increase wastewater generation
B)
Conserve water resources
C)
Increase runoff
D)
Reduce evaporation
Rainwater harvesting is the collection and storage of rainwater for later use or for groundwater recharge. Its main purpose is to conserve water resources by reducing dependence on external water sources and improving water availability. Option (a) is incorrect because it does not increase wastewater generation. Option (c) is incorrect because harvesting aims to reduce runoff, not increase it. Option (d) may happen indirectly in some systems, but it is not the primary aim.
The most common material used for septic tank construction is:
A)
Timber
B)
Steel sheet
C)
RCC
D)
Plastic
Septic tanks are commonly constructed using Reinforced Cement Concrete (RCC) because it is strong, durable, waterproof when properly built, and suitable for underground sewage storage. Timber is unsuitable due to decay, steel sheet is prone to corrosion, and plastic is used only in some prefabricated systems, not as the most common material.
If the contact resistance of a circuit breaker is high, the immediate risk is:
A)
Nuisance tripping
B)
Excessive heating
C)
Incorrect settings
D)
Reduced capacity
High contact resistance in a circuit breaker causes extra power loss at the contacts, which is dissipated as heat. This can quickly lead to overheating, insulation damage, contact deterioration, and even failure. Nuisance tripping, incorrect settings, and reduced capacity are not the immediate direct effect of high contact resistance.