JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech IV Year UTILIZATION OF ELECTRICAL ENERGY Previous Question Paper (January/February - 2023 - R18)
Note: i) Question paper consists of Part A, Part B. ii) Part A is compulsory, which carries 25 marks. In Part A, Answer all questions. iii) In Part B, Answer any one question from each unit. Each question carries 10 marks and may have a, b as sub questions.
Part A
What is dielectric heating?
Answer
Dielectric heating, also known as high-frequency capacitive heating, is a process in which electrical energy is used to heat non-conducting materials (dielectrics) by placing them in a high-frequency alternating electric field. The heating effect is caused by the dielectric loss resulting from the rapid polarization and depolarization of molecules within the material, which generates internal heat due to molecular friction.
State the applications of the direct and indirect type of arc furnaces.
Answer
Arc furnaces are classified based on the method of heat transfer to the charge. Their applications are as follows:
Direct Arc Furnace: In this type, the arc is formed directly between the electrodes and the charge itself. The current flows through the charge, providing intense, localized heating. It is primarily used for the melting and refining of steel and high-melting-point alloys where rapid, high-temperature processing is required.
Indirect Arc Furnace: In this type, the arc is formed between two electrodes above the charge, and heat is transferred to the charge primarily through radiation and convection. It is typically used for melting non-ferrous metals like copper, brass, and bronze, where a lower, more uniform temperature is needed to prevent overheating or chemical changes in the melt.
Why positive side of d.c supply meant for electroplating is earthed?
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State the various applications of electrolysis.
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A lamp emits 500 lumens in all the directions. What is its M.S.C.P?
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What are the various factors involved in the street lighting?
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What is kando system?
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Explain the terms: (i) Adhesive weight and (ii) Train resistance.
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Explain the traction power supply system in India.
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What type of batteries are used in train lighting?
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Part B
Describe the construction and working of an induction furnace suitable for melting and refining of non-ferrous metals.
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Explain the construction and principle of working of direct resistance heating.
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Compare the ac and dc system of metallic arc welding.
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Discuss the various characteristics required of welding generator sets (Both of the ac and of the dc types) and state how arc stabilization is achieved in practical welding generator sets.
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Discuss the principle of arc welding and the difference between carbon and metallic arc welding and their relative merits.
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Describe with a circuit diagram the working of a fluorescent lamp. Enumerate its advantages and disadvantages. Explain how its disadvantages can be overcome.
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An indoor badminton court is accommodated in a hall 20 meters long, 10 meters wide and 15 meters high. The walls and ceiling of the hall are painted black and do not reflect any light. Design a scheme for providing an average illumination of 80 lux at ground surface, using 200W tungsten filament lamps with suitable fittings. Give reasons for your choice. Coefficient of utilization = 0.5. Efficiency of lamps = 15 lumens per watt.
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A schedule speed of 30 km per hour is required between stops one km apart. Find the maximum speed over the run if the stop is of 20 seconds duration. The values of acceleration and retardation are 2.5 kmphps respectively. Assume a simplified speed-time curve.
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What are the factors affecting the scheduled speed of a train?
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Enumerate the factors which effect specific energy consumption of trains operation at a given scheduled speed.
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An electric train while going down an incline of 1 in 150 has the following speed-time curve: i) Starting from rest a uniform acceleration of 2.5 kmphps for 30 sec, ii) Steady speed for 40 sec (with mechanical breaking), iii) Coasting for 50 sec and iv) Breaking at a rate of 3.5kmphps. Assume the track resistance as 40 Nw per tonne, allowance for rotational inertia 8%, overall efficiency 75%, calculate the specific energy consumption.
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Explain various methods of obtaining unidirectional polarity constant output in train lighting scheme.
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Discuss the special requirements of train lighting.
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