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Past Questions
Which conductor is commonly used in 11kV line?
A)
Weasel
B)
Gnat
C)
Panther
D)
Grasshopper
In electrical transmission and distribution, ACSR (Aluminum Conductor Steel Reinforced) conductors are named using a standardized nomenclature (often based on animal names) to denote their size and capacity. For 11kV distribution lines, which are typically used for secondary transmission or primary distribution, a conductor with a relatively small cross-sectional area is required. The 'Weasel' conductor is a standard small-sized ACSR conductor commonly utilized for 11kV lines due to its appropriate current-carrying capacity and mechanical strength for short-span distribution. 'Panther' and 'Grasshopper' are typically larger conductors used for higher voltage transmission lines (like 33kV, 66kV, or 132kV) where higher current capacity and greater mechanical strength are necessary to support longer spans.
Which of the following distribution systems is more reliable?
A)
Radial system
B)
Tree system
C)
Ring main system
D)
All are equally reliable
In electrical distribution, reliability refers to the ability of the system to maintain power supply to consumers even during a fault.
1. **Radial System (Option a):** This is the simplest system where power flows from a single source to consumers along a single path. If a fault occurs at any point in the line, all consumers downstream of that fault lose power. Therefore, it has the lowest reliability.
2. **Tree System (Option b):** This is essentially an extension of the radial system with multiple branches. While it covers more area, it still lacks redundancy; a fault on a main branch disconnects all subsequent sub-branches.
3. **Ring Main System (Option c):** In this system, the distribution transformer is fed by a loop (ring) that returns to the source. This provides two paths for the current to reach any given point. If a fault occurs in one section of the ring, that section can be isolated, and power can still be supplied to all consumers from the alternative path. This redundancy significantly increases the reliability of the system.
Therefore, the Ring Main System is the most reliable among the given options.
Temporary connection shall be granted for a maximum period of _______ at a time.
A)
30 days
B)
3 months
C)
6 months
D)
45 days
According to the JERC (Joint Electricity Regulatory Commission) regulations governing the supply code of practice for the North Eastern states (including Mizoram), a temporary connection is provided for specific short-term requirements such as construction work, festivals, or exhibitions. The standard regulatory provision specifies that a temporary connection shall be granted for a maximum period of 6 months at a time. If the requirement extends beyond this period, the consumer must apply for an extension or convert the connection into a permanent one, subject to the approval of the licensee/department.
The SI unit of Power is:
A)
Hertz
B)
Watt
C)
Ampere
D)
Candela
Power is defined as the rate at which work is done or energy is transferred over time. In the International System of Units (SI), the unit of power is the Watt (W), named after James Watt. One Watt is defined as one Joule per second (1 W = 1 J/s).
Analysis of other options:
- a. Hertz (Hz): The SI unit of frequency (cycles per second).
- c. Ampere (A): The SI unit of electric current.
- d. Candela (cd): The SI unit of luminous intensity.
The overall average per unit subsidized tariff in the prevailing Tariff is:
A)
Rs. 8.05
B)
Rs. 7.82
C)
Rs. 7.10
D)
Rs. 6.82
The overall average per unit subsidized tariff in the prevailing tariff is Rs. 7.82, so option **b** is correct. The other options are incorrect because they do not match the computed/quoted average tariff value: **a (Rs. 8.05)** is higher than the prevailing average, **c (Rs. 7.10)** is lower, and **d (Rs. 6.82)** is also lower. Hence, the correct answer is **b**.
A Voltmeter is connected in _______with the circuit component across which Potential difference is to be measured.
A)
Series
B)
Parallel
C)
Series or Parallel
D)
None of the above
1. Definition of Potential Difference: Potential difference (voltage) is the difference in electrical potential between two distinct points in an electrical circuit. To measure this difference, an instrument must be connected to both points simultaneously.
2. Connection Method: To measure the voltage across a component without altering the current flowing through that component, a voltmeter must be connected in parallel. This allows the voltmeter to experience the same potential difference as the component.
3. Ideal Characteristics: An ideal voltmeter has infinite internal resistance. By connecting it in parallel, it ensures that negligible current flows through the meter, preventing it from loading the circuit or changing the voltage it is intended to measure.
4. Why other options are incorrect:
- (a) Series: If a voltmeter were connected in series, its high resistance would drastically reduce the total current in the circuit, effectively acting as an open circuit and preventing the device under test from functioning.
- (c) Series or Parallel: A voltmeter cannot be used in series for voltage measurement as it would disrupt the circuit operation.
Transformer oil must be free from:
A)
odour
B)
gases
C)
sulphur
D)
moisture
Transformer oil serves two primary purposes: insulation and cooling. Moisture is the most critical contaminant because it significantly reduces the dielectric strength (breakdown voltage) of the oil. The presence of water molecules allows for the formation of conductive paths, which can lead to internal arcing and catastrophic failure of the transformer. While gases (like dissolved hydrogen or methane) are indicators of faults, and sulphur can cause corrosion, moisture is the fundamental impurity that must be strictly removed during the oil filtration and degassing process to ensure the operational safety and longevity of the insulation system. Therefore, transformer oil must be absolutely free from moisture.
Under the Electricity Act, 2003, who is a ‘consumer’?
A)
A person using electricity for residential purposes
B)
A person who purchases electricity for any purpose
C)
A bulk purchaser of electricity
D)
Anyone using power from the grid
According to Section 2(15) of the Electricity Act, 2003, a 'consumer' is defined as any person including a distributor who purchases or hires electricity for any purpose.
- Option (a) is incorrect because it is too narrow; residential use is only one type of consumption.
- Option (c) is incorrect because while a bulk purchaser is a consumer, the definition of 'consumer' is broader and encompasses all purchasers regardless of volume.
- Option (d) is incorrect because 'using power from the grid' is a general description, whereas the legal definition specifically hinges on the act of 'purchasing' or 'hiring' electricity.
As per JERC(M&M) Electricity Supply Code Regulation 2013, any of the following documents or its attested copies, shall not be considered as acceptable proof of identity for individual in respect to application of new service connection:
A)
Electoral identity card
B)
PAN Card
C)
Registered General Power of Attorney
D)
Ration Card
According to the JERC (Joint Electricity Regulatory Commission) Electricity Supply Code Regulations, when applying for a new service connection, the applicant must provide valid Proof of Identity (POI) and Proof of Ownership/Occupancy.
1. Electoral Identity Card, PAN Card, and Passport are universally accepted as primary government-issued photo identity proofs because they verify the identity of the individual.
2. A Registered General Power of Attorney is accepted as a legal document to establish the authority of an individual to apply on behalf of the owner.
3. A Ration Card is primarily a document for the distribution of essential commodities and serves as a proof of residence/address in some contexts, but it is NOT considered a valid 'Proof of Identity' (POI) for the purpose of establishing the legal identity of an individual in formal electricity connection applications, as it often lacks standardized biometric or secure identity verification compared to the other options listed.
The efficiency of a transformer will be maximum when:
A)
copper losses = hysteresis losses
B)
eddy current losses = copper losses
C)
hysteresis losses>eddy current losses
D)
copper losses = iron losses
In a transformer, total losses consist of two main components:
1. Iron Losses (Core Losses): These include hysteresis and eddy current losses. They are considered constant losses because they depend on the supply voltage and frequency, not the load.
2. Copper Losses (Ohmic Losses): These occur in the windings due to resistance and are variable losses, as they vary with the square of the load current (I²R).
Mathematically, Efficiency (η) = (Output Power) / (Output Power + Constant Losses + Variable Losses).
To find the maximum efficiency, we differentiate the efficiency expression with respect to the load current and set it to zero. This calculus derivation proves that maximum efficiency occurs when the variable losses (copper losses) are exactly equal to the constant losses (iron losses).
Analysis of options:
- Option (a) and (b) are incorrect because they only compare one part of the iron loss to copper loss, rather than the total iron loss.
- Option (c) is a general statement about the composition of iron losses and does not determine the point of maximum efficiency.
- Option (d) correctly identifies the condition: Copper Losses = Iron Losses.
Transformer oil used in transformer provides:
A)
insulation and cooling
B)
cooling and lubrication
C)
lubrication and insulation
D)
insulation, cooling and lubrication
Transformer oil (mineral oil) serves two primary functions in a power transformer:
1. **Insulation**: It acts as a dielectric medium between the windings and the grounded tank, as well as between the turns of the windings, preventing electrical arcing and short circuits.
2. **Cooling**: It acts as a heat transfer medium. As the transformer operates, heat is generated in the core and windings due to hysteresis, eddy currents, and I2R losses. The oil absorbs this heat and carries it away via convection to the radiator or cooling fins, where it is dissipated into the surrounding air or water.
Regarding the other options: Lubrication is not a requirement for the internal components of a transformer because there are no moving mechanical parts (like gears or pistons) within the tank that require lubrication. Therefore, options b, c, and d are incorrect.
Distribution transformers are usually designed to have maximum efficiency:
A)
at 50% of full load
B)
at 75% of full load
C)
near full load
D)
near no load
1. Efficiency of a transformer is maximum when the variable losses (copper losses) are equal to the constant losses (iron/core losses).
2. Power transformers are typically designed for maximum efficiency near full load because they operate at a relatively constant load.
3. Distribution transformers, however, are connected to the grid to supply end-users. The load on these transformers varies significantly throughout the day (peaking during evening hours and dropping significantly at night).
4. Since the average load of a distribution transformer is much lower than its rated full-load capacity, they are specifically designed to achieve maximum efficiency at a lower loading point—typically between 50% and 75% of full load—to minimize overall energy losses over a 24-hour cycle.
5. While some textbooks mention 50%, the industry standard for modern distribution transformer design typically targets the 60% to 75% range to balance capital cost and operational efficiency.
A CRO is used to measure:
A)
Voltage
B)
Frequency
C)
Phase
D)
All of the above
A Cathode Ray Oscilloscope (CRO) is a versatile electronic instrument used to visualize and analyze electrical signals.
1. Voltage: The CRO measures voltage by observing the vertical displacement (amplitude) of the waveform on the screen. By multiplying the number of vertical divisions by the Volts/Div setting, the peak-to-peak or RMS voltage can be determined.
2. Frequency: The CRO measures the time period (T) of a signal by observing the horizontal distance of one complete cycle. Since frequency (f) is the reciprocal of the time period (f = 1/T), the frequency can be accurately calculated.
3. Phase: By using the dual-trace mode (comparing two different signals on the same screen), the time shift between two waveforms can be measured. This time difference, relative to the period, allows for the calculation of the phase difference between the two signals.
Since the CRO can measure all three parameters, option 'd' is the correct choice.
Hydroelectric power plant is mainly located in ____________.
A)
Flat areas
B)
Deserts
C)
Hilly areas
D)
Deltas
Hydroelectric power generation relies on the conversion of potential energy of water into electrical energy. The amount of power generated is proportional to the 'head' (the vertical distance the water falls). Hilly and mountainous areas provide the necessary natural elevation changes to create high-head reservoirs and steep drops, which are essential for driving turbines efficiently.
Why other options are incorrect:
- Flat areas: Lack the necessary elevation (head) to generate significant power without massive, expensive artificial pumping or pumping-storage systems.
- Deserts: Generally lack the consistent and abundant water sources (rivers/streams) required for hydroelectric plants.
- Deltas: These are low-lying areas where rivers slow down and split; they lack the steep gradients required for hydroelectric power generation.
Ampere is SI unit of:
A)
Current
B)
Voltage
C)
Frequency
D)
Power
The Ampere (symbol: A) is the base unit of electric current in the International System of Units (SI). It is defined as the flow of one coulomb of electric charge per second (1 A = 1 C/s).
Analysis of other options:
- b. Voltage: The SI unit of voltage (electric potential difference) is the Volt (V).
- c. Frequency: The SI unit of frequency is the Hertz (Hz).
- d. Power: The SI unit of power is the Watt (W).
What is the primary purpose of grounding in LV electrical installations?
A)
Voltage control
B)
Equipment cooling
C)
Personnel safety and equipment protection
D)
Power factor correction
Grounding (or earthing) in Low Voltage (LV) electrical installations is primarily implemented to ensure safety.
1. Personnel Safety: By connecting the non-current-carrying metal parts of equipment to the earth, any insulation failure that causes the metal casing to become energized will create a low-resistance path to ground. This triggers protective devices (like circuit breakers or fuses) to trip, preventing electric shock to personnel who might touch the equipment.
2. Equipment Protection: Grounding helps stabilize voltage levels during surges and provides a path for fault currents to dissipate safely, preventing catastrophic equipment failure.
Why other options are incorrect:
- Option (a) Voltage control: While grounding helps stabilize voltage relative to earth, 'voltage control' usually refers to regulators or transformers.
- Option (b) Equipment cooling: Cooling is handled by heat sinks, fans, or liquid cooling systems, not by electrical grounding.
- Option (d) Power factor correction: This is achieved using capacitor banks or synchronous condensers, not by grounding.
Which of the following is the main field of application of pin type insulator?
A)
Distribution system
B)
Transmission system
C)
Transmission and distribution system
D)
EHV transmission system
Pin type insulators are designed to be mounted on the cross-arms of poles, where the conductor is tied to the top of the insulator. Due to their design and material constraints, they are generally economical and effective only for voltages up to 33 kV. In modern power systems, voltages above 33 kV (Transmission systems and EHV systems) require suspension or strain insulators to handle the higher electrical stress and provide necessary flexibility. Therefore, pin type insulators are primarily used in the distribution system (typically 11 kV and 33 kV lines) rather than high-voltage transmission systems.
- Option (b) is incorrect because transmission systems usually operate at higher voltages (66kV, 132kV, etc.) where suspension insulators are used.
- Option (c) is incorrect because they are not suitable for the high-voltage side of the transmission system.
- Option (d) is incorrect because EHV (Extra High Voltage) systems require massive insulator strings (suspension type) to prevent flashovers.
Concrete cover is provided to protect the steel reinforcement against:-
A)
Corrosion
B)
Shrinkage
C)
Buckling
D)
Dust
Concrete cover is the distance between the outer surface of the concrete and the outer surface of the reinforcement. Its primary purposes are: 1. Protection against Corrosion: Steel is prone to rusting (oxidation) when exposed to moisture, oxygen, and chlorides. The alkaline nature of concrete creates a passive layer around the steel; the cover ensures this layer remains intact and prevents external corrosive agents from reaching the reinforcement. 2. Fire Resistance: It protects the steel from losing strength rapidly during a fire.
Why other options are incorrect:
- b. Shrinkage: Shrinkage is a property of the concrete mix itself (loss of moisture); cover does not prevent the concrete from shrinking.
- c. Buckling: Buckling is a structural failure of slender members under compression; it is prevented by lateral bracing and proper design, not by concrete cover.
- d. Dust: While cover physically separates steel from dust, dust is not a structural threat to reinforcement; corrosion is the critical chemical threat.
Where does the neutral axis by Working Stress Method of the reinforced beam pass through?
A)
Centre of gravity of the concrete section
B)
Centroid of the transformed section
C)
Centroid of the concrete section
D)
Centroid of the structure
In the Working Stress Method (WSM) of reinforced concrete design, the beam is analyzed based on the principle of linear elasticity. Since concrete and steel have different moduli of elasticity (E_s and E_c), the steel area is replaced by an equivalent area of concrete that would provide the same stiffness. This is done using the modular ratio (m = E_s / E_c). The resulting section, consisting of the concrete area and the 'transformed' steel area, is known as the Transformed Section. The neutral axis is the axis about which the section bends and where the stress is zero; for a linearly elastic material, this axis must pass through the centroid of the entire transformed section.
Why other options are incorrect:
- Option (a) and (c): The center of gravity or centroid of the concrete section alone ignores the contribution of the reinforcement, which shifts the neutral axis downward.
- Option (d): 'Centroid of the structure' is a general term referring to the entire building or assembly, not the specific cross-section of the beam.
The stone suitable for rubble masonry should be:-
A)
Hard
B)
Tough
C)
Heavy
D)
Light
In rubble masonry, stones are used in their natural or roughly dressed state. For a structure to be durable and capable of bearing loads, the stones must possess high compressive strength and resistance to wear and weathering. 'Hardness' is the primary property that ensures the stone does not crumble under pressure or erode over time.
Analysis of options:
- (a) Hard: Correct. Hardness ensures durability and strength, which are essential for load-bearing masonry.
- (b) Tough: While toughness (resistance to fracture) is a positive trait, hardness is the fundamental requirement for the overall stability and longevity of rubble masonry.
- (c) Heavy: Weight is a characteristic of the stone's density, not necessarily a requirement for suitability. Excessively heavy stones can make construction difficult without adding structural value.
- (d) Light: Light stones are generally avoided in load-bearing rubble masonry as they often lack the necessary strength and stability.
The least cover provided in beam is:-
A)
20 mm
B)
25 mm
C)
30 mm
D)
15 mm
In Reinforced Cement Concrete (RCC) design, 'cover' refers to the distance between the outer surface of the concrete and the outer surface of the reinforcement. This cover is essential to protect the steel from corrosion and to provide fire resistance. According to standard codes of practice (such as IS 456:2000), the nominal cover for beams is generally specified as 25 mm for mild exposure conditions. While slabs may have a smaller cover (e.g., 15-20 mm) and columns or foundations may have larger covers (40-50 mm), the standard minimum nominal cover for a beam in general construction is 25 mm. Therefore, among the given options, 25 mm is the recognized standard least cover for beams.
The Small Hydel Project without reservoirs where water is used at the rate at which it runs in the river is called:-
A)
Diversion weir
B)
Pump storage pump
C)
Run-of-the-river
D)
Head loss
A Run-of-the-river (ROR) hydroelectric project is a type of hydroelectric generation where little or no water storage is provided. Instead of using a large reservoir (dam) to store water for later use, the plant utilizes the natural flow and elevation drop of the river to generate electricity. The water is diverted from the river, passed through a turbine, and returned to the river downstream.
Analysis of other options:
- a. Diversion weir: This is a structure used to divert water from a river into a canal or penstock, but it is a component of a project, not the name of the project type itself.
- b. Pump storage pump: This refers to a system that stores energy by pumping water from a lower reservoir to an upper reservoir during low demand and releasing it during peak demand; it requires reservoirs.
- d. Head loss: This is a hydraulic term referring to the reduction in the total head (pressure) of a fluid as it moves through a system due to friction or turbulence; it is not a type of project.
The excess power available over the firm power during the off peak hours is:-
A)
Firm power
B)
Secondary power
C)
Installed capacity
D)
Peak load
In hydroelectric power plant terminology, power is categorized based on its reliability and availability:
1. **Firm Power**: This is the minimum amount of energy that a power plant can guarantee to deliver to the grid continuously throughout the year, regardless of the season or water availability.
2. **Secondary Power**: This is the power available over and above the firm power. It is typically available during the off-peak hours or during periods of high water inflow (monsoon). Because it depends on water availability and is not guaranteed 100% of the time, it is termed 'secondary'.
3. **Installed Capacity**: This is the maximum theoretical power output the plant can produce if all turbines are running at full capacity; it is a physical limit, not a category of available power over firm power.
4. **Peak Load**: This refers to the maximum demand placed on the electrical grid at a specific time, not the power generated by the plant.
Therefore, the excess power available over the firm power is defined as Secondary Power.
In a mortar, the binding material is:-
A)
Cement
B)
Sand
C)
Surkhi (Brick dust)
D)
Cinder
Mortar is a mixture of a binding material, a fine aggregate, and water.
1. Binding Material: This is the component that undergoes a chemical reaction (hydration) to harden and bind the aggregate particles together. Common binding materials include Cement, Lime, or Gypsum. In modern construction, Cement is the most widely used binding agent.
2. Fine Aggregate: This is the filler material that provides bulk and reduces shrinkage. Examples include Sand, Surkhi (brick dust), or Cinder.
Evaluating the options:
- Option (a) Cement: Correct. It acts as the glue/binder that holds the mortar together.
- Option (b) Sand: Incorrect. Sand is the fine aggregate (filler).
- Option (c) Surkhi: Incorrect. Surkhi is a pozzolanic material used as a substitute for sand (fine aggregate).
- Option (d) Cinder: Incorrect. Cinder is used as a lightweight fine aggregate.
The fuel for Small Hydel Project is:-
A)
Water
B)
Petrol
C)
Hydrogen
D)
Diesel
A Small Hydel Project (Small Hydroelectric Project) is a system that generates electricity by harnessing the kinetic and potential energy of flowing or falling water. In this context, 'fuel' refers to the primary energy source that drives the turbine. Water flows through a penstock to rotate a turbine, which in turn rotates a generator to produce electricity. Unlike thermal power plants, hydroelectric projects do not consume chemical fuels; they utilize the natural water cycle.
- Option b (Petrol), Option c (Hydrogen), and Option d (Diesel) are chemical fuels used in internal combustion engines or fuel cells, which are not the energy source for a hydroelectric project.