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Past Questions
Demand factor is
A)
Minimum power demand to maximum power demand
B)
Average power demand to total connected load of the system
C)
Maximum power demand to total connected load of the system
D)
Average power demand to maximum power demand
Demand factor is defined as the ratio of maximum demand to the total connected load. It indicates how much of the connected load is actually used at the time of peak demand. Therefore, option (c) is correct. Option (a) is incorrect because it describes a ratio involving minimum demand, which is not the definition of demand factor. Option (b) is the load factor-related idea, not demand factor. Option (d) is also incorrect because average demand divided by maximum demand is not demand factor.
Number of disc insulators needed to form strings for 33 kV (tension or dead ending assembly) is
A)
2
B)
3
C)
6
D)
12
For a 33 kV line, the usual suspension or tension string uses 3 disc insulators. In standard transmission-line practice, 11 kV generally needs 1 disc, 33 kV needs 3 discs, 66 kV needs 4 discs, and 132 kV needs 8 discs (approximate standard values). Hence, for 33 kV dead-ending/tension assembly, the correct answer is 3.
Hydrogen cooling is employed in:
A)
Turbo Generators only
B)
Water wheel Generators only
C)
Can be used in both turbo generators and water wheel generators
D)
None of these
Hydrogen cooling is used in large turbo generators because hydrogen has high thermal conductivity, low density, and low windage losses, making it ideal for cooling high-speed rotating machines. Water wheel generators (hydro generators) are generally air-cooled or water-cooled by other arrangements, not hydrogen-cooled. Therefore, the correct answer is Turbo Generators only.
A conductor made up of a number of wires twisted together is
A)
Bunched conductor
B)
Shaped conductor
C)
Multi-core conductor
D)
Stranded conductor
A conductor made up of a number of wires twisted together is called a stranded conductor. This construction improves flexibility and is commonly used in power and electrical applications. A bunched conductor is a type of stranded arrangement but the standard term for wires twisted together is stranded conductor. Shaped conductor refers to a conductor with a specific cross-sectional shape, and multi-core conductor means several insulated conductors combined in one cable.
Which of the following factors is not the cause of breakdown at normal voltage?
A)
Detorioration of insulation
B)
Accidental short circuiting by tree branches
C)
Surges caused by lightning
D)
Damage perching of birds
Breakdown at normal voltage is usually caused by external or accidental factors such as tree branches short-circuiting lines, lightning surges, or bird perching causing flashover. Deterioration of insulation is generally a gradual internal aging problem and is not a direct cause of breakdown at normal operating voltage.
In order to improve the power factor the following device is employed in the substation
A)
Synchronous Condenser
B)
Synchronous Reactor
C)
Series Capacitors
D)
None of these
A synchronous condenser is used in substations to improve power factor by supplying reactive power (VARs) to the system. It operates as an over-excited synchronous machine and helps compensate inductive loads. A synchronous reactor is used to absorb reactive power, so it does not improve power factor. Series capacitors are mainly used for transmission line compensation, not as the standard substation device for power factor improvement.
Post insulators are used for
A)
Supporting bus bars in switchgear
B)
Insulating guard wires
C)
High-voltage suspension lines
D)
Insulating stay wires
Post insulators are rigid insulators used to support and isolate bus bars and other live parts in switchgear and substations. They are not used for guard wires, suspension lines, or stay wires. Suspension lines use suspension insulators, and stay wires use stay insulators.
Sub-Stations can be classified based on the following:
A)
Voltage level & Configuration
B)
Applications & Structure
C)
Insulation & Switching
D)
Allofthese
Sub-stations are commonly classified on multiple bases, including voltage level, configuration, application, structure, insulation, and switching arrangement. Since all the listed bases are valid classification methods, the correct answer is 'All of these'. Options (a), (b), and (c) each mention only part of the full classification, so they are incomplete.
Hydrogen cooling employed in large thermal power plant alternator:
A)
Increases the insulation life
B)
Decreases the insulation life
C)
Does not effect the insulation life
D)
None of these
Hydrogen is used as a cooling medium in large alternators because it has high thermal conductivity, low density, and low windage losses. Better cooling keeps the machine temperature lower, and lower operating temperature reduces thermal stress on insulation. Hence, hydrogen cooling increases insulation life. Options (b) and (c) are incorrect because insulation life is strongly affected by temperature.
Where more than one multicore cable is laid in the same trench, a desirable horizontal inter-axial spacing is
A)
less than 0.1m
B)
0.1 to 0.2m
C)
0.25 to 0.4m
D)
more than 0.4m
When more than one multicore cable is laid in the same trench, a horizontal inter-axial spacing of about 0.1 to 0.2 m is considered desirable. This spacing helps reduce mutual heating and allows safer cable operation. Spacing less than 0.1 m is too close, while 0.25 m or more is generally larger than the usual desirable range for this arrangement.
Load curve are plotted between
A)
Time and Demand
B)
Current and Load
C)
Power and Voltage
D)
Load and Voltage
A load curve is a graph showing how the electrical load (demand) varies with time. Hence it is plotted between time on the x-axis and demand/load on the y-axis. The other options do not represent the standard definition of a load curve.
The machine which converts mechanical energy into electrical energy is:
A)
Governor
B)
Generator
C)
Turbine
D)
Power House
A generator converts mechanical energy into electrical energy by electromagnetic induction. A governor controls speed, a turbine converts fluid energy into mechanical energy, and a power house is the building/facility where power generation equipment is installed.
A Sub-station is a part of an electrical
A)
Generation
B)
Transmission
C)
Distribution
D)
Allofthese
A sub-station is an important part of the power system and can be used in generation, transmission, and distribution networks. It may step up voltage at generating stations, step down voltage in transmission systems, or distribute power to consumers. Hence, it is part of all these sections.
PVC stands for
A)
Polyethylene Vinyl Cable
B)
Poly Vacuum Cable
C)
Poly Vinyl Chloride
D)
Polythene Vacuum Chloride
PVC is the standard abbreviation for Poly Vinyl Chloride, a widely used plastic insulation material in electrical cables. The other options are incorrect because they expand PVC into non-standard or meaningless terms.
The term used for conveyance of electric power at extra-high voltages from generating stations to the grid sub-stations is:
A)
Transformation
B)
Transmission
C)
Generation
D)
Distribution
Electric power conveyed at extra-high voltages from generating stations to grid substations is called transmission. Transmission is used for bulk transfer of power over long distances at high voltage to reduce losses. Generation means producing electricity, transformation means changing voltage levels using transformers, and distribution refers to supplying power from substations to consumers at lower voltages.
Which of the following is digital transducer?
A)
Encoder
B)
Thermistor
C)
LVDT
D)
Strain gauge
A digital transducer gives output in digital form. An encoder converts mechanical position or motion into a digital code, so it is a digital transducer. Thermistor, LVDT, and strain gauge are analog transducers because they produce continuous output changes.
Earthing conductivity is affected by:
A)
Moisture content in the soil
B)
Chemical composition
C)
Concentration of salts in the soil
D)
All ofthese
Earthing conductivity depends on the soil’s ability to conduct current. This is influenced by moisture content, chemical composition, and the concentration of salts in the soil. Moist soil and higher salt content generally reduce resistance and improve conductivity. Therefore, all the given factors affect earthing conductivity.
Poles suitable for lines upto 66 kV is
A)
Wood Poles
B)
R.C.C. Poles
C)
Steel tubular poles
D)
Steel towers
For distribution and sub-transmission lines up to about 66 kV, steel tubular poles are commonly used because they provide adequate mechanical strength and durability. Wood poles are generally used for lower-voltage lines, while steel towers are preferred for higher-voltage transmission lines above 66 kV. R.C.C. poles are also used in distribution, but steel tubular poles are the standard suitable choice for lines up to 66 kV.
Which of the following devices is employed in substation to limit the short circuit current in the power system?
A)
Shunt condenser
B)
Reactor
C)
Series capacitor
D)
Shunt capacitor
A reactor is used in substations to limit short-circuit current by adding inductive reactance in series with the system. This increases the impedance during fault conditions and reduces the fault current. A shunt condenser, series capacitor, and shunt capacitor are used mainly for power factor improvement, voltage support, or reactive power compensation, not for limiting short-circuit current.
A megger indicates infinity when test terminals are open-circuited. This is because
A)
No current flows through the current coil
B)
No current flows through the pressure coil
C)
No current flows through the compensating winding
D)
Current does not flow through current coil and pressure coil
A megger measures insulation resistance. When the test terminals are open-circuited, the resistance is effectively infinite, so no current flows through the current coil. In a megger, the deflection to infinity corresponds to zero current in the current coil. The pressure coil is not the reason for this indication, and the compensating winding is not relevant here.
A prime mover in which gradual changes in the momentum of a fluid are utilised to produce rotation of the mobile member is
A)
Electric Motor
B)
Turbine
C)
Diesel Engine
D)
None of these
Step-by-step reasoning: 1. Definition of a Prime Mover: A prime mover is a machine that converts energy from a natural source (like fluid, heat, or wind) into mechanical energy. 2. Analysis of the mechanism: The question specifies that 'gradual changes in the momentum of a fluid' are used to produce rotation. According to Newton's Second Law of Motion, a change in momentum of a fluid (whether liquid or gas) exerts a force on the blades of the machine. 3. Evaluating the options: (a) Electric Motor: Converts electrical energy into mechanical energy using electromagnetic induction, not fluid momentum. (b) Turbine: A rotary mechanical device that extracts energy from a fluid flow (water, steam, or air) and converts it into useful work. The fluid's momentum changes as it passes through the turbine blades, creating the torque required for rotation. (c) Diesel Engine: An internal combustion engine that converts chemical energy from fuel into mechanical energy via reciprocating pistons, not through the gradual change of fluid momentum to rotate a mobile member. Therefore, the turbine is the only device that fits the description.
Which one is not elements of cost
A)
Materials
B)
Labour
C)
Expenses
D)
None of these
In Industrial Engineering and Cost Accounting, the total cost of a product or service is traditionally broken down into three primary 'Elements of Cost'. These are:
1. **Materials**: This includes all raw materials, components, and supplies used in the production process (e.g., steel for a machine, plastic for a casing).
2. **Labour**: This refers to the human effort (wages and salaries) paid to workers who are directly or indirectly involved in the production process.
3. **Expenses**: This includes all other costs that are not materials or labour, such as factory rent, electricity, depreciation of machinery, and insurance.
Since Materials (a), Labour (b), and Expenses (c) are all fundamental elements of cost, none of the listed options are 'not' elements of cost. Therefore, the correct answer is 'None of these'.
Cetane number of Diesel oil normally available in market is in the range
A)
45 - 50
B)
60-65
C)
75 - 80
D)
90 - 100
1. Definition: The Cetane Number (CN) is a measure of the ignition quality of diesel fuel. It indicates the ignition delay period; a higher cetane number means a shorter ignition delay, leading to smoother combustion and easier cold starts.
2. Standard Diesel Fuel: Commercial diesel fuel available in the market is typically a blend of hydrocarbons. While pure n-cetane has a CN of 100 and alpha-methylnaphthalene has a CN of 0, standard automotive diesel is formulated to balance performance and stability.
3. Typical Range: For most commercial diesel engines, a cetane number in the range of 40 to 55 is considered standard. Specifically, the range 45-50 is the most common benchmark for general-purpose diesel oil available in the market.
4. Analysis of Options:
- Option (a) 45-50: Aligns with standard commercial diesel specifications.
- Option (b) 60-65: This is higher than standard commercial diesel and is usually reserved for premium or specialized high-cetane fuels.
- Option (c) 75-80: Extremely high; not typical for general market diesel.
- Option (d) 90-100: This represents nearly pure n-cetane, which is not commercially viable as a standalone fuel for standard engines.
The resultant upward thrust experienced by a body when immersed in the fluid is known as
A)
Equilibrium of floating bodies
B)
Buoyancy
C)
Weight of a body
D)
None of these
Step-by-step reasoning: 1. Definition: According to Archimedes' Principle, when a body is partially or fully immersed in a fluid, it experiences an upward force exerted by the fluid. This upward force is equal to the weight of the fluid displaced by the body. 2. Terminology: This resultant upward force is technically termed as the 'Buoyant Force' or 'Buoyancy'. 3. Analysis of options: (a) Equilibrium of floating bodies refers to the state where the buoyant force equals the weight of the body, not the force itself. (b) Buoyancy is the correct term for the upward thrust. (c) Weight of a body is the downward force acting due to gravity, which opposes the buoyant force. Therefore, option (b) is the correct answer.
Arrange the words given below in a meaningful sequence: 1. Word 2. Paragraph 3. Sentence 4. Letters 5. Phrase
A)
4,1,5,2,3
B)
4,1,3,5,2
C)
4, 2,5, 1,3
D)
4, 1,5, 3,2
To arrange these words in a meaningful sequence, we must look at the hierarchical structure of language, moving from the smallest unit to the largest unit.
1. Letters (4): The smallest building blocks of written language.
2. Word (1): A group of letters combined to form a meaning.
3. Phrase (5): A group of words that function together but do not necessarily form a complete thought.
4. Sentence (3): A group of words/phrases that express a complete thought.
5. Paragraph (2): A group of sentences focused on a single topic.
Following this logic, the sequence is: Letters → Word → Phrase → Sentence → Paragraph.
Numerically, this corresponds to: 4, 1, 5, 3, 2.
Comparing this to the options:
- Option (a) 4,1,5,2,3: Incorrect (Paragraph comes before Sentence).
- Option (b) 4,1,3,5,2: Incorrect (Sentence comes before Phrase).
- Option (c) 4,2,5,1,3: Incorrect (Paragraph comes before Word).
- Option (d) 4,1,5,3,2: Correct.