Btech Utilization of Electrical Energy and Electric Traction KEE-079 Aktu Short Question Pdf Notes

Explore B.Tech AKTU Quantum Book Short Question Notes on Utilization of Electrical Energy and Electric Traction. Discover the principles of energy-efficient systems and learn about electric mobility technologies.

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Unit-I: Electric Heating (Short Question)

Q1. What are the applications of high frequency eddy current heating ?

Ans. 1. Surface hardening

2. Annealing

3. Soldering.

Q2. How is control of power affected in electric arc furnaces ?

Ans. The power input to arc furnaces can be regulated by adjusting the voltage provided to the arc furnace (by changing the tapping on the supply transformer).

Q3. What are the advantages of electric heating ?

Ans. i. Electric heating equipment is less expensive; it does not require highly qualified personnel, thus maintenance costs are lower.

ii. The temperature of this heating may be precisely controlled and regulated, either manually or automatically.

Q4. Write the Stefan’s law of heat radiation and label all constants.

Ans. The amount of heat radiated from the source to the target object is mostly determined by their temperature differences. Heat radiated from the source follows a law derived by Stefan which mathematically states that:

where Stefan’s constant is 5.7195 x 104

T1 = Absolute temperature of radiating surface in kelvin (K)

T2 = Absolute temperature of absorbing surface in kelvin (K)

K = Radiating efficiency and is constant

= 1 for single element

= 0.5 to 0.8 for several elements placed side by side

e = Emissivity

= 1 for perfectly black body

= 0.9 for resistance heating elements.

Q5. What is heat transfer and name its various modes ?

Ans. Heat transfer is defined as the transmission of energy from one region to another as a result of temperature gradient takes place by the following three methods:

• i. Conduction
• ii. Convection

Q6. What is an oven?

Ans. Oven is a low temperature heating chamber with provision for ventilation.

Q7. What are the essential requirements of heating elements ?

Ans. i. High-specific resistance.

ii. High-melting point.

Q8. What are the causes of the failure of the heating elements ?

Ans.

• i. The formation of hotspots.
• ii. The oxidation of the element and the intermittency of operation.
• iii. The embitterment caused by gain growth.
• iv. Contamination and corrosion.

Q9. How can rate of dielectric heating be varied ?

Ans. The rate of dielectric heating can be changed by adjusting the supply voltage or frequency.

Q10. What are the various reasons of losses occurring in resistance oven ?

Ans. Losses occurring due to :

• i. The heat used in raising the temperature of oven or furnace.
• ii. The heat used in raising the temperature of containers (or) carriers.
• iii. The heat conducted through the walls.

Q11. What is pinch effect ?

Ans. The pinch effect refers to the production of bubbles and voids in the charge to be heated by electromagnetic induction due to high-electromagnetic forces, which causes the secondary circuit to be interrupted.

Q12. Write any two advantages of dielectric heating.

Ans. i The heating of non-conducting materials is very rapid.

ii. The uniform heating of material is possible.

iii. Heat is produced in the whole mass of the material.

Q13. List out some of the applications of dielectric heating.

Ans.

• i. The drying of paper, wood, etc.
• ii. The gluing of wood.
• iii. The heat-sealing of plastic sheets.
• vi. The heating for general processing such as coffee, roasting and chocolate industry.
• v. The heating for dehydration such as milk, cream, and vegetables.

Q14. What is the main advantage of a ‘direct are furnace’ ?

Ans. The fundamental advantage of a direct arc furnace is that it produces purer output and allows for precise control of composition during the refining process.

Q15. How power input is controlled in a ‘submerged arc furnace’?

Ans. Power is controlled by varying the voltage applied to arc furnace.

Ans.

• i. Compactness of heating units
• ii. Rapid heating
• iii. Flexibility
• iv. Safety.

Unit-II: Electric Welding (Short Question)

Q1. What is welding ?

Ans. Welding is the technique of putting two pieces of metal together so that bonding occurs at their original boundary surfaces.

Q2. What is main drawback of electron beam process ?

Ans. Pressure build up in vacuum chamber causes electrical breakdown.

Q3. Why alternating current is found most suitable for resistance welding ?

Ans. AC is better suited to resistance welding because it can deliver any desired combination of current and voltage via a transformer.

Q4. What is meant by welding electrode ?

Ans. An electrode is a filler metal in the shape of a wire or rod that is either bare or uniformly coated with flux.

Q5. What are the advantages of electrical welding ?

Ans. i. Welding is the most economical method to permanently join two metal parts.

ii. It provides design flexibility.

iii. The welding equipment is not so costly.

Q6. What is the field of application of butt welding ?

Ans. Butt welding is used for welding steel rails with cross-sectional areas as large as 6.25 cm2

Q7. What are the applications of ‘flash welding’ ?

Ans. In automotive building, flash welding is commonly employed on the body, axles, wheels, frames, and other parts. It’s also used to weld motor frames, transformer tanks, and a variety of sheet steel containers like barrels and floats.

Q8. What is ‘arc blow’ in electric arc welding ?

Ans. Arc blow is the deflection of the arc from the weld site. This problem only occurs with DC welding equipment and is most visible while welding with base electrodes.

Q9. On what factors do the type of electrode depends ?

Ans.

• i. The type of metal to be welded
• ii. The welding position
• iii. The type of electric supply (AC or DC)
• iv. The type of the welding machine.

Q10. Name the type of generator which is used in electric arc welding.

Ans. Differential compound wound DC generator.

Q11. List out the disadvantages of electric welding.

Ans. i. The welding gives out harmful radiations and fumes.

ii. The welding needs internal inspection.

iii. Skilled welding is necessary to produce good welding.

Q12. List out the factors based on which the electric welding can be carried out properly.

Ans.

• i. The type of metal to be joined.
• ii. The techniques of welding adopted.
• iii. The cost of equipment used.
• iv. The nature of products to be fabricated.

Q13. What is meant by spot welding ?

Ans. Spot welding is the act of connecting two metal sheets and fusing them together between copper electrode tips at appropriately spaced intervals utilising a strong electric current carried through the electrodes.

Q14. What is meant by seam welding ?

Ans. Seam welding is simply a sequence of continuous spot welding. Seam welding occurs when the number of spots obtained by spot welding are set so tightly that they can overlap.

Q15. List out the factors which effect the successful welding operation.

Ans. i. Welding time

ii. Welding current

iii. Welding pressure.

Q16. What is the fundamental difference between the electric arc welding and the resistance welding?

Ans. Resistance welding differs from arc welding in that pressure is used rather than filler metal or fluxes.

Q17. What are the uses of electrolysis ?
Ans. This process is commonly employed in the extraction of pure metals from their ores, metal refining, and the rebuilding of damaged parts in the metallurgical, chemical, and other sectors.

Q18. Give the principle of electrolysis.

Ans. The basic premise of electrolysis is that when a direct current electric current is passed through a salt solution, some metals can be removed from it. These separated metals can be coated to form a pure thin layer on any item.

Q19. What is meant by electro-deposition ?

Ans. Electro-deposition is the technique of depositing one metal over another metal or nonmetal using electrolysis.

Q20. State Faraday’s first law of electrolytic process.

Ans. The mass of substance deposited from an electrolyte is proportional to the amount of electricity travelling through the electrolyte in a particular time, according to this law.

Q21. State Faraday’s second law of electrolysis.

Ans. When the same amount of electric current is carried through different electrolytes, the masses of the compounds deposited are proportionate to their respective chemical equivalents or equivalent weights, according to this law.

Q22. List out various applications of electrolytic process.

Ans.

• i. The production of caustic soda.
• ii. Electrometallurgy.
• iii. Electro refining.
• iv. Electro-deposition.

Q23. What is the use of electroplating?

Ans. Electroplating is commonly used to protect metals from corrosion caused by ambient air, moisture, and CO2

Unit-III: Illumination (Short Question)

Q1. Why is tungsten selected as the filament material ?

Ans. Tungsten is the most often used metal for filament because of its high melting point (3400 °C), high resistivity, low temperature coefficient (0.0051), low vapour pressure, and ability to bear vibration during operation.

Q2. Why does the efficiency of a filament lamp increase with the increase in operating voltage ?

Ans. The efficiency of a lamp (lumens/watt) improves with increasing voltage due to temperature increase and is proportional to the square of the voltage.

Q3. The flux emitted by a lamp in all directions is 1000 lumens. Calculate its mscp.

Ans.

Q4. What is flood lighting ?

Ans. It means flooding of large surface areas with light from powerful projector.

Q5. Define the term ‘illumination’.

Ans. Illumination is the luminous flux received by a surface per unit area. The unit is ‘lux’ and ‘metre-candle’.

Q6. State the laws of illumination.

Ans. 1. Law of inverse square: The illumination of a surface is inversely proportional to the square of the distance between the surface and the light source, provided that the distance is large enough for the source to be considered a point source.

2. Lambert’s cosine law: This law states that the illumination at any point on a surface is proportional to the cosine of the angle between the normal at that point and the direction of light flux.

Q7. What is the need of polar curves ?

Ans. Due to their asymmetrical shapes, most lights on light sources do not have an even distribution of light intensity. Knowing how light is distributed in different directions is frequently required to understand how a light source’s candle power varies in various directions. Polar curves are able to quantify the luminance intensity in all directions.

Q8. What are the characteristics which a lighting scheme should possess ?

Ans.

• 1. It should provide adequate illumination.
• 2. It should provide light distribution all over the working plane as uniform as possible.
• 3. It should avoid glare and hard shadows as far as possible.
• 4. It should provide light of suitable colour.

Q9. What are discharge lamps ?

Ans. 1. Electric discharge through these lamps causes gas or vapour to glow. The colour and intensity of light emitted, i.e., candle power, are solely determined by the type of the gas or vapour.

2. These lamps are luminescent-light lamps, and their efficiency is not affected by temperature. In this regard, they differ significantly from incandescent bulbs, whose efficiency is temperature dependant.

Q10. What is an ‘arc lamp’?

Ans. 1. In an arc lamp, an electric current is made to flow across two electrodes that are drawn apart from each other. As a result, an arc is formed. The arc keeps the current flowing and is a particularly efficient source of light.

2. These lamps are utilised in searchlights, projection lamps, and other special-purpose lamps, such as those used in flash cameras.

Q11. Define the mscp.

Ans. It is defined as the mean of the source’s candle power in all directions in the horizontal plane.

Q12. Define the mhcp.

Ans. It is defined as the mean of the candle power of the source in all directions in all planes.

Q13. What are the factors that lead to the efficient air-conditioning ?

Ans. i Temperature control.

ii. Humidity control.

iii. Air movement and circulation.

Q14. Define luminous flux.

Ans. It is defined as the energy radiated per second by a luminous body in the form of light waves. It is denoted by the symbol ‘ɸ’ and is measured in lumens.

Q15. Define luminous intensity.

Ans. Luminous intensity in a given direction is defined as the luminous flux emitted by the source per unit solid angle.

Q16. Define illumination.

Ans. Illumination is defined as the luminous flux received by the surface per unit area.

Q17. Define lamp efficiency.

Ans. It is defined as the wattage ratio of the source’s total luminous flux to its electrical power input.

Q18. Mention any two reasons why tungsten is preferred to carbon as filament material.

Ans.

• i. Working temperature of tungsten is 2500-3000 °C.
• ii. Its resistance at working temperature is about 12-15 times the cold resistance.
• iii. It has positive temperature coefficient of resistance of 0.0045.
• iv. Its resistivity is 5.6-12.5 μΩ-cm.

Q19. List out the properties should be possessed by the filament material.

Ans.

• i. High melting point.
• ii. Low temperature coefficient.
• iii. Highly resistive nature.
• iv. Sufficient mechanical strength to withstand vibrations.

Q20. What is meant by refrigeration ?

Ans. It is the controlled reduction of an object’s temperature from its typical surrounding temperature in order to cool it.

Q21. Give some of the applications of refrigeration.

Ans. i. The making of ice.

ii. The air-conditioning of industries.

iii. The metal manufacturing and their treatment.

Q22. What is meant by air-conditioning ?

Ans. Air-conditioning is the process of controlling the temperature, humidity, purity, and circulation of air in a closed space.

Unit-IV: Electric Traction-I (Short Question)

Q1. Why the magnetic circuit of a traction motor is not made of cast iron ?

Ans. Because it has less mechanical strength and cannot withstand continuous vibrations.

Q2. What is meant by the term adhesive weight ?

Ans. It is the total weight to be carried out on the drive in the wheels of locomotive.

Q3. What is meant by schedule speed of a train ?

Ans. It is the ratio of the entire distance travelled between two points and the total time spent running between them.

Q4. What are the most important requirements of suburban line railway service ?

Ans. 1. Average distance between two stops is 1 to 8 km.

2. High rates of acceleration and retardation are necessary.

Q5. What is meant by speed-time curve ?

Ans. It is the train’s speed at various points after the start of the run. The movement of trains and their energy consumption can be studied easily using speed-time curves.

Q6. Why single phase system is preferred for main line railway service ?

Ans. Because it results minimum cost with high transmission efficiency.

Q7. Mention advantages of electric drives.

Ans.

• i. They have comparatively long life as compared to mechanical drive.
• ii. It is cleaner., as there are no flue gases etc.
• iii. Itis economical.
• iv. They have flexible control characteristics.

Q8. What is electric traction system ?

Ans. The traction system is the system that drives the propulsion of a vehicle and obtains the driving power or tractive force from various devices such as electric motors, steam engine drives, diesel engine dives, and so on.

Q9. Mention a few advantages of electric traction.

Ans. i. Maintenance and operating costs are quite minimal.

ii. The electric motor’s speed can be easily controlled.

iii. Regenerative braking allows energy to be fed back into the supply system during the braking period.

Q10. What are the requirements of ideal traction system ?

Ans. i. An ideal traction system should be capable of producing high tractive effort in order to achieve quick acceleration.

ii. Traction motor speed control should be simple.

iii. Vehicles should be able to travel on any route without stopping.

Q11. What are the various system of track electrification ?

Ans.

• i. DC system.
• ii. Single-phase AC system.
• iii. Three-phase AC system.
• iv. Composite system.

Q12. What are the causes lead to composite system ?

Ans. In terms of distribution costs, 1ɸ AC system is preferred; in DC systems, DC series motors have the most desirable features; and in 3ɸ systems, 3ɸ induction motors have the advantage of automatic regenerative braking. As a result, the benefits of DC/AC and 3ɸ/1ɸ systems must be combined. The aforementioned cause results in the evolution of a composite system.

Q13. What are the various types of passenger services ?

Ans. i. City or urban service

ii. Suburban service

iii. Main line service.

Q14. Which of the system (DC or AC) is preferred for suburban services and road transport where stops are frequent and distances of run are small ?

Ans. DC system.

Q15. What are the most important requirements of the main line railway service ?

Ans. i. High maximum (crest) speed

ii. Minimum cost of overhead structure.

Q16. Which system is preferred for main line railway service ?

Ans. Single-phase system.

Q17. What are the factors which affect the specific energy consumption of a train running at a given schedule speed ?

Ans.

• i. Acceleration
• ii. Retardation
• iii. Maximum speed
• iv. Distance between stops
• v. Track configuration
• vi. Type of train and equipment.

Q18. Differentiate between ‘crest speed’ and ‘average speed.

Ans.

Q19. By which factors the schedule speed of a train is affected ?

Ans. i. Acceleration and retardation

ii. Maximum or crest speed

iii. Duration of stop.

Q20. What is ‘coefficient of adhesion’ ?

Ans. The coefficient of adhesion is defined as the ratio of tractive effort required to slip the wheels to the weight of the adhesive.

Q21. What is the effect of increase in speed on coefficient of adhesion ?

Ans. The coefficient of adhesion decreases with increase in speed.

Q22. What is ‘specific energy output’ ?

Ans. Specific energy output is the energy output of the driving wheel given in watt-hours (Wh) per tonne-kilometer (t-km) of train.

Q23. What is ‘specific energy consumption’?

Ans. Specific energy consumption is defined as the amount of energy spent (Wh) per tonne mass of the train per km of run length.

Unit-V: Electric Traction-II (Short Question)

Q1. Why DC series motor ideally suited for traction purposes ?

Ans. Because a DC series motor has a high starting torque and slows with increasing load, it is instantly freed of hefty excessive load.

Q2. Name the motors which find application in traction.

Ans.

• i. DC series motors
• ii. AC series motors
• iii. Repulsion motor
• iv. Three-phase induction motors
• v. Linear induction motors.

Q3. What is the major disadvantage of DC motor ?

Ans. The existence of a commutator and brushes requires frequent maintenance, especially when flashovers at the commutator occur owing to severe voltage changes.

Q4. Which braking is not possible in diesel electric ?

Ans. Regenerative braking.

Ans. Metadynes are machines that have more than two brush sets per pair of poles. It is a device that converts constant voltage and variable current power into constant current and variable voltage power.

Q6. Under what circumstances series-parallel method of speed control of DC series traction motors adopted?

Ans. When motors employed are two, four, six or more than this even.

Q7. What are the advantages of thyristor control of traction motors ?

Ans.

• i. Accurate control and fast response.
• ii. Elimination of bulky on-load tap changer and electromagnetic devices.
• iii. Saving of energy
• iv. Minimum wear and tear.

Q8. Give advantages of diesel engine.

Ans.

• 1. It requires less amount of oil per km than amount of coal per km in steam engine.
• 2. It consumes small amount of water.
• 3. Power loss in speed control is low.
• 4. Good for places where coal mines are far away.

Q9. Give disadvantages of diesel engine.

Ans.

• 1. High initial cost.
• 2. High weight.
• 3. Low life.
• 4. Regenerative braking is not possible.
• 5. They do not have high starting torque.

Q10. Name various diesel electric traction systems.

Ans. i. A diesel engine-powered DC generator powers a DC series motor.

ii. Three-phase alternator powered by a diesel engine and providing DC series traction motors via a semiconductor diode rectifier.

iii. A diesel engine-powered alternator powers squirrel-cage motors via a diode rectifier and a three-phase voltage source inverter.