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Past Questions — 2025
What is the unit of measurement for earthwork volume?
A)
Square meters
B)
Liters
C)
Cubic meters
D)
Tons
In civil engineering estimation and costing, the unit of measurement is determined by the dimension of the item being measured. Earthwork (which includes excavation and filling) involves three dimensions: length, width, and depth/height. Therefore, the volume is calculated as (Length × Width × Depth), and the standard SI unit for volume is the cubic meter (m³).
Analysis of other options:
- Square meters (a) is a unit of area, used for items like plastering, painting, or flooring.
- Liters (b) is a unit of liquid volume, not used for bulk earthwork in construction.
- Tons (d) is a unit of mass/weight, used for materials like steel or aggregate when purchased by weight, but not for the measurement of earthwork volume in site estimation.
Per capita demand depends on:
A)
Climate and living standards
B)
Soil type
C)
Roof slope
D)
Street width
Per capita demand refers to the average amount of water required by one person per day. This demand is influenced by several socio-economic and environmental factors:
1. Climate: In hot and dry regions, water consumption increases due to higher bathing frequency, gardening, and cooling requirements compared to cold regions.
2. Living Standards: Higher income levels and urban lifestyles typically lead to higher water usage (e.g., use of washing machines, dishwashers, and flushing toilets).
3. Other factors include industrialization, quality of water, and metering.
Why other options are incorrect:
- Soil type (b) affects the seepage and infiltration of water in pipes or drainage, but not the amount of water a person demands for consumption.
- Roof slope (c) is relevant for calculating rainwater harvesting potential or runoff, not per capita water demand.
- Street width (d) is a town planning parameter and has no direct correlation with the individual water consumption of a person.
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 prevalent in Northeast India, specifically designed to be earthquake-resistant. The primary characteristics of this construction style include: 1. Lightweight materials: To minimize damage during seismic activity, heavy masonry is avoided. 2. Timber Framing: The main structural framework (posts and beams) is made of timber (wood). 3. Walls: The walls are typically made of 'Ikra' (a type of reed) or bamboo slats plastered with mud or cement. 4. Roofing: The roofs are steeply pitched to drain heavy monsoon rains and are covered with corrugated galvanized iron (CGI) sheets. Therefore, the combination of timber for the structure and corrugated roofing is the defining characteristic. Option (a) is incorrect as RCC and stone are heavy and not characteristic of this style. Option (c) is partially correct but incomplete as GI sheets are only for the roof, not the whole building. Option (d) is incorrect as glass and steel are modern industrial materials.
Silicon steel used in laminations mainly reduces-
A)
hysteresis loss
B)
eddy current losses
C)
copper losses
D)
all of the above
In a transformer core, core losses consist of two main components: Hysteresis loss and Eddy current loss.
1. **Hysteresis Loss:** This occurs due to the friction between magnetic domains during the reversal of magnetization in each AC cycle. Silicon steel (a silicon-alloyed steel) is used because it has a narrow hysteresis loop (low coercivity and low retentivity), which significantly reduces the energy dissipated as heat during these cycles. Therefore, the addition of silicon specifically targets the reduction of hysteresis loss.
2. **Eddy Current Loss:** These are circulating currents induced in the core material. While silicon increases the electrical resistivity of the steel (which helps), the primary method used to reduce eddy current losses is the use of **laminations** (thin sheets insulated from each other) to break the current paths.
3. **Copper Loss:** These are $I^2R$ losses occurring in the windings, not the core. The material of the core (silicon steel) has no effect on copper losses.
Since the question asks specifically what the use of **Silicon steel** (the material) reduces, the primary answer is hysteresis loss. (Note: While silicon also increases resistivity to help with eddy currents, the 'laminations' part of the core design handles the bulk of eddy current reduction, whereas the 'silicon' part of the material handles the hysteresis reduction).
Ammeter is used for measuring-
A)
Voltage
B)
Current
C)
Resistance
D)
None of the above
An ammeter is a specialized instrument designed specifically to measure the electric current flowing through a circuit. To measure current, an ammeter must be connected in series with the load so that the full current flows through the device. It is designed with very low internal resistance to ensure that it does not significantly affect the current it is intended to measure.
Analysis of other options:
- Option (a) Voltage: Measured using a Voltmeter, which is connected in parallel.
- Option (c) Resistance: Measured using an Ohmmeter.
- Option (d) None of the above: Incorrect, as option (b) is the standard definition.
How many Consumer Category are there in the prevailing Tariff?
A)
6
B)
8
C)
10
D)
12
In the prevailing electricity tariff structure implemented by the Power and Electricity Department, Government of Mizoram, consumers are categorized based on the nature of their electricity usage to ensure equitable billing. The 8 standard consumer categories typically include: 1. Domestic (Residential), 2. Commercial, 3. Industrial, 4. Agricultural, 5. Public Lighting/Street Lighting, 6. Government/Institutional, 7. Temporary Connections, and 8. Special Categories (such as Low Tension/High Tension distinctions or specific subsidized groups). This classification allows the department to apply different tariff rates (slabs) based on the socio-economic impact and energy intensity of the category.
Earth wire or ground wire is made of-
A)
Copper
B)
Aluminium
C)
Iron
D)
Galvanised Steel
In the context of electrical power distribution and transmission (which is the focus of a Junior Engineer exam for a Power Electricity Department), 'Earth wire' or 'Ground wire' typically refers to the overhead shield wire installed at the topmost position of transmission towers to protect phase conductors from lightning strikes. These wires are primarily made of Galvanised Steel (GS) because they require high mechanical tensile strength to span long distances between towers and must be resistant to atmospheric corrosion. While copper is an excellent conductor, it is too expensive and lacks the necessary mechanical strength for overhead spans. Aluminium is used for phase conductors but is not the standard for overhead ground wires due to strength requirements. Plain iron would corrode rapidly. Therefore, Galvanised Steel is the industry standard for overhead earth wires.
The objective of earthing or grounding is-
A)
to provide a low resistance path to the ground
B)
to provide a high resistance path to the ground
C)
to provide flow of positive, negative and zero sequence currents
D)
none of the above
Earthing or grounding is the process of connecting the non-current carrying parts of electrical equipment or the neutral point of a supply system to the general mass of earth.
1. Why Option (a) is correct: The primary objective of earthing is safety. In the event of an insulation failure or a fault (such as a phase-to-body fault), the fault current must be diverted away from the human body and the equipment. According to Ohm's Law (V=IR), a low resistance path ensures that the fault current flows easily to the ground, which triggers protective devices (like fuses or circuit breakers) to trip quickly, thereby isolating the fault and preventing electric shocks.
2. Why Option (b) is incorrect: A high resistance path would impede the flow of fault current. This would prevent protective devices from tripping and could leave the metallic chassis of the equipment energized at a dangerous voltage, increasing the risk of fatal electric shocks to personnel.
3. Why Option (c) is incorrect: While zero sequence currents do flow through the ground during unbalanced faults, the 'objective' of earthing is not to facilitate the flow of all sequence components (positive, negative, and zero), but specifically to provide a safe return path for fault currents to ensure system stability and personnel safety.
The efficiency of a transformer will be maximum when-
A)
copper losses = hysteresis losses
B)
hysteresis losses = eddy current losses
C)
eddy current losses = copper losses
D)
copper losses = iron losses
The efficiency of a transformer is defined as the ratio of output power to input power. The total losses in a transformer 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 due to the resistance of the windings and are variable losses because they vary with the square of the load current (I²R).
Mathematically, Efficiency (η) = Output / (Output + 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 loss (copper loss) is exactly equal to the constant loss (iron loss).
Analysis of options:
- Option a, b, and c are incorrect because they compare specific components of the core loss or mix core loss with copper loss. Hysteresis and eddy current losses together make up the total iron loss; the condition for maximum efficiency is not based on their individual equality, but on the equality of the total iron loss to the total copper loss.
In a tap changing transformer, the tappings are provided on-
A)
primary winding
B)
secondary winding
C)
high voltage winding
D)
any of the above
In a tap changing transformer, tappings are provided to regulate the output voltage by changing the turns ratio. While theoretically, tappings could be placed on either winding, in practical engineering and industrial applications, they are almost always provided on the High Voltage (HV) winding for the following reasons: 1. Current Magnitude: The current in the HV winding is significantly lower than in the Low Voltage (LV) winding. Since the tap changer is a mechanical switch, lower current reduces the risk of arcing and wear and tear on the contacts. 2. Cost and Complexity: Implementing a tap changer on a high-current LV winding would require much heavier and more expensive switchgear to handle the high current. 3. Efficiency: Small changes in the number of turns on the HV side produce the desired voltage regulation more effectively. Therefore, while 'any of the above' might seem logically possible in a lab setting, the standard technical answer for power systems is the high voltage winding.
Which of the following distribution systems is more reliable?
A)
Radial system
B)
Tree system
C)
Ring main system
D)
All are equally reliable
Reliability in a distribution system refers to the ability to maintain power supply to consumers even in the event of a fault in a section of the network.
1. **Radial System (Option a):** In this system, power flows from a single source to the consumers along a single path. If a fault occurs at any point in the line, all consumers downstream of that fault lose power. This makes it the least reliable system.
2. **Tree System (Option b):** This is essentially an extension of the radial system where the main feeder branches off into several sub-feeders. While it covers more area, it still lacks redundancy; a fault on a main branch disconnects all subsequent branches.
3. **Ring Main System (Option c):** In this system, the distribution transformer is fed by a loop (ring) of conductors. Every distribution point is fed from two directions. If a fault occurs in any section of the ring, that specific section can be isolated, and power can still reach all consumers via the alternative path of the ring. This redundancy significantly increases the reliability of the power supply.
Therefore, the Ring Main system is the most reliable among the given options.
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, a device must be connected to both points simultaneously.
2. Voltmeter Characteristics: An ideal voltmeter has infinite internal resistance, and a practical voltmeter has very high internal resistance. This ensures that it does not draw significant current from the circuit, which would otherwise alter the voltage it is trying to measure.
3. Connection Method: To measure the voltage across a component, the voltmeter must be connected in parallel. This allows the voltmeter to experience the same potential difference as the component.
4. Why other options are incorrect:
- (a) Series: If a voltmeter were connected in series, its high resistance would drastically reduce the total current flowing through the circuit, effectively acting as an open circuit and preventing the circuit from functioning normally.
- (c) Series or Parallel: A voltmeter cannot be used in series for voltage measurement purposes due to the reasons mentioned above.
- (d) None of the above: Option (b) is the standard and correct electrical engineering practice.
Meggar is an instrument used for-
A)
measuring current
B)
measuring voltage
C)
measuring power
D)
testing insulation
A Megger (short for Mega-ohmmeter) is a specialized instrument used to measure very high electrical resistance, typically in the range of Mega-ohms (MΩ). Its primary application is to test the insulation resistance of electrical equipment such as cables, motor windings, and transformers. It works by applying a high DC voltage to the insulation and measuring the resulting leakage current to determine the resistance.
Why other options are incorrect:
- Option (a): Current is measured using an Ammeter.
- Option (b): Voltage is measured using a Voltmeter.
- Option (c): Power is measured using a Wattmeter.
Which of the following does not change in a transformer?
A)
Current
B)
Voltage
C)
Frequency
D)
All of the above
A transformer is a static electrical device that transfers electrical energy between two or more circuits through electromagnetic induction.
1. **Voltage (Option b):** The primary purpose of a transformer is to change the voltage level. Depending on the turns ratio (N2/N1), it can be a 'step-up' transformer (increasing voltage) or a 'step-down' transformer (decreasing voltage).
2. **Current (Option a):** According to the principle of conservation of energy (assuming an ideal transformer where Power In = Power Out, i.e., V1*I1 = V2*I2), if the voltage is increased, the current must decrease proportionally, and vice versa. Therefore, current changes.
3. **Frequency (Option c):** The frequency of the alternating current is determined by the source (the generator). Since a transformer does not have any rotating parts or active power electronics to modify the timing of the AC cycle, the frequency of the output voltage is identical to the frequency of the input voltage.
Therefore, frequency remains constant in a transformer.
Cells are connected in series in order to-
A)
increase the voltage rating
B)
increase the current rating
C)
increase life of the cell
D)
None of the above
In electrical circuits, when cells (voltage sources) are connected in series, the total voltage of the battery is the algebraic sum of the individual voltages of each cell. For example, if three cells of 1.5V each are connected in series, the total voltage becomes 1.5V + 1.5V + 1.5V = 4.5V.
Analysis of options:
- Option (a) is correct because series connection increases the total electromotive force (EMF) or voltage rating.
- Option (b) is incorrect because to increase the current rating (capacity/Ah), cells must be connected in parallel. In a series connection, the current remains the same as that of a single cell.
- Option (c) is incorrect because connecting cells in series does not inherently increase the chemical life or cycle life of an individual cell; in fact, if one cell fails or is weaker, it can lead to uneven discharge and potentially shorten the overall battery pack's reliability.
- Option (d) is incorrect as option (a) is the standard electrical principle.
The power factor of industrial loads is generally-
A)
unity
B)
lagging
C)
leading
D)
zero
Industrial loads are predominantly composed of inductive loads. The most common equipment in industrial settings includes induction motors, transformers, and solenoid valves. In an inductive circuit, the current lags behind the voltage due to the magnetic field requirements of the coils. Since the majority of the power consumed in industries is used to drive motors (which are inductive), the overall power factor of an industrial load is generally 'lagging'.
Analysis of other options:
- Unity (a): This occurs when the load is purely resistive (e.g., heaters), which is rare for an entire industrial plant.
- Leading (c): This occurs when the load is predominantly capacitive (e.g., large capacitor banks), which is usually only seen during power factor correction or in specific electronic loads.
- Zero (d): This would imply a purely reactive circuit with no real power consumption, which is not possible for a functional industrial load.
Pelton turbines are used for-
A)
medium head applications
B)
low head applications
C)
in steam power plants
D)
for high head applications
A Pelton turbine is an impulse turbine where the entire available head is converted into kinetic energy via a nozzle before the water hits the buckets on the runner. Because it relies on high-velocity jets of water to generate power, it is most efficient and typically used in 'high head' scenarios (usually above 300 meters).
Analysis of other options:
- Option (a) and (b): Medium and low head applications typically utilize Reaction Turbines, such as Francis turbines (medium head) or Kaplan turbines (low head), which utilize both pressure and kinetic energy.
- Option (c): Pelton turbines are hydraulic turbines used for hydroelectric power, not for steam power plants (which use steam turbines).
The voltage of the single phase supply to residential consumers is-
A)
110 V
B)
210 V
C)
230 V
D)
400 V
In the Indian electrical power system (which governs the Government of Mizoram's electricity department), the standard nominal voltage for single-phase residential supply is 230 V AC at a frequency of 50 Hz.
Step-by-step analysis of options:
1. Option (a) 110 V: This is the standard voltage used in North American countries (USA, Canada), not in India.
2. Option (b) 210 V: This is not a standard nominal voltage for residential distribution.
3. Option (c) 230 V: This is the correct standard nominal voltage for single-phase supply in India, as per the Bureau of Indian Standards (BIS) and the Central Electricity Authority (CEA) guidelines.
4. Option (d) 400 V: This is the standard nominal line-to-line voltage for a three-phase supply in India, not the single-phase supply provided to residential consumers.
As per JERC(M&M) Electricity Supply Code Regulation 2013, Supply of LT Single Phase category shall be upto a contracted load of _______ kW.
A)
10
B)
6
C)
8
D)
4
According to the JERC (M&M) Electricity Supply Code Regulations 2013, the guidelines for the supply of electricity specify the limits for single-phase and three-phase connections to ensure grid stability and prevent phase imbalance. For Low Tension (LT) supply, the Single Phase category is permitted for consumers with a contracted load up to 6 kW. If the contracted load exceeds 6 kW, the consumer is required to be provided with a Three Phase connection to distribute the load evenly across the phases of the distribution system. Therefore, option (b) 6 is the correct limit.
Pin type insulators are generally not used for voltages beyond-
A)
1.1 kV
B)
11 kV
C)
22 kV
D)
33 kV
Pin type insulators are designed to support the conductor on the cross-arm of the pole. As the voltage level increases, the size of the insulator must increase to maintain the necessary creepage distance and prevent flashover. For voltages up to 33 kV, pin insulators are practically feasible. However, beyond 33 kV, the size and weight of a pin insulator become prohibitively large and expensive, making them mechanically unstable. Therefore, for voltages above 33 kV, suspension-type insulators (strings of porcelain discs) are used instead, as they provide better flexibility and can be easily scaled by adding more discs to handle higher voltages. Thus, pin type insulators are generally not used for voltages beyond 33 kV.
Iron loss in the transformer can be determined by-
A)
Short Circuit Test
B)
Open Circuit Test
C)
Both a) and b)
D)
None of the above
In a transformer, total losses are divided into Iron losses (Core losses) and Copper losses.
1. **Iron Loss (Core Loss):** This consists of Hysteresis and Eddy current losses. These losses depend on the magnetic flux density, which is determined by the applied voltage. In an Open Circuit (OC) test, the rated voltage is applied to one winding (usually the Low Voltage side) while the other winding remains open. Since the secondary is open, the current drawn is very small (no-load current), making the copper losses negligible. Therefore, the power measured by the wattmeter during an OC test represents the Iron loss of the transformer.
2. **Copper Loss:** This is the $I^2R$ loss occurring in the windings. This is determined by the Short Circuit (SC) test, where the rated current is passed through the winding while the voltage is kept very low, making the iron losses negligible.
Therefore, the Open Circuit Test is specifically used to determine the iron loss.
Generally grounding is provided for-
A)
only for the safety of the equipment
B)
only for the safety of the operating personnel
C)
both (a) and (b)
D)
none of the above
Grounding (or earthing) is a fundamental safety practice in electrical engineering designed to achieve two primary objectives:
1. Safety of Operating Personnel: By providing a low-resistance path to the earth, grounding ensures that if a fault occurs (such as a phase-to-frame fault), the leakage current is diverted to the ground rather than passing through a human body. This prevents electric shocks and fatalities.
2. Safety of Equipment: Grounding helps in stabilizing the voltage during normal operation and provides a path for fault currents to flow, which triggers protective devices (like circuit breakers or fuses) to trip quickly. This prevents the equipment from overheating or sustaining permanent damage due to overvoltage or sustained fault conditions.
Since grounding serves both the protection of people and the protection of the hardware, option (c) is the correct choice.
Which conductor is commonly used as a neutral conductor in LT distribution line?
A)
Weasel
B)
Gnat
C)
Ant
D)
Grasshopper
In ACSR (Aluminum Conductor Steel Reinforced) conductor nomenclature, conductors are named after animals or insects, and their sizes are categorized by their cross-sectional area.
1. **Ant Conductor**: This is a small-sized ACSR conductor commonly used as a neutral conductor in Low Tension (LT) distribution lines because the neutral conductor typically carries less current than the phase conductors under balanced loads and does not require the same current-carrying capacity as the main phases.
2. **Weasel, Gnat, and Grasshopper**: While these are also names of ACSR conductors, they differ in size and application. For instance, 'Dog' or 'Rabbit' are larger conductors used for higher voltage transmission or main distribution phases. In the specific context of standard LT distribution practices in many power utilities (including those following traditional ACSR naming conventions), the 'Ant' conductor is the standard choice for the neutral wire due to its appropriate gauge and cost-effectiveness for that specific role.
The chemical used in breather is-
A)
asbestos fiber
B)
silica sand
C)
sodium chloride
D)
silica gel
In a transformer, the oil expands and contracts due to temperature changes. When the oil contracts, air from the atmosphere is drawn into the conservator tank. This air contains moisture, which can degrade the dielectric strength of the transformer oil. To prevent this, the air is passed through a 'breather' containing silica gel. Silica gel is a highly hygroscopic substance (a desiccant) that absorbs moisture from the air before it enters the tank. Fresh silica gel is typically blue in color and turns pink when it becomes saturated with moisture, indicating that it needs to be replaced or reactivated.
Why other options are incorrect:
- a. Asbestos fiber: Used for thermal insulation or fireproofing, not for moisture absorption.
- b. Silica sand: While it contains silica, it does not have the porous structure or chemical properties required to act as an effective desiccant.
- c. Sodium chloride: This is common table salt; it is not used as a desiccant in transformer breathers.
Four resistors each of 3 ohm are connected in series, the equivalent resistance of the system will be-
A)
4/3 Ohm
B)
12 Ohm
C)
6 Ohm
D)
3/4 Ohm
Step-by-step calculation:
1. Identify the given values: There are four resistors, each with a resistance (R) of 3 ohms.
2. Identify the connection type: The resistors are connected in 'series'.
3. Apply the formula for equivalent resistance (Req) in a series circuit: Req = R1 + R2 + R3 + ... + Rn.
4. Substitute the values: Req = 3 Ω + 3 Ω + 3 Ω + 3 Ω = 12 Ω.
Analysis of options:
- Option (a) 4/3 Ohm: This would be the result if the resistors were connected in parallel (1/Req = 1/3 + 1/3 + 1/3 + 1/3 = 4/3, so Req = 3/4, but 4/3 is the reciprocal).
- Option (b) 12 Ohm: Correct, as per the series addition formula.
- Option (c) 6 Ohm: Incorrect calculation.
- Option (d) 3/4 Ohm: This is the correct equivalent resistance if the resistors were connected in parallel (Req = R/n = 3/4).