Utilization of Electrical Energy 2018 Question Paper — Government Col…
The 2018 Utilization of Electrical Energy previous year question paper (Government College of Engineering and Technology, Jammu), with every question and its marks.
- University: Government College of Engineering and Technology, Jammu
- Subject: Utilization of Electrical Energy
- Course: ELECTRICAL ENGINEERING—COURSE NO.—EEE-701 (A) (Utilization of Electrical Energy)
- Year: 2018
- Paper: end-term
- Duration: 180 minutes
- Total marks: 100
Instructions
- Attempt five questions in all, selecting at least two questions from each Section.
- Assume suitable data wherever missing.
- Use of calculator is allowed.
Questions
Section-A
- Q1. (a) Compare between DC and AC systems of railway electrification from the point view of main line and suburban line railway service. (10) (b) An electric train is to have acceleration and braking retardation of $0.8\text{ km/h/s}$ and $3.2\text{ km/h/s}$ respectively. If the ratio of maximum to average speed is $1.3$ and time for stops $26$ seconds, find schedule speed for a run of $1.5\text{ km}$. Assume simplified trapezoidal speed-time curve. (10) [20 marks]
- Q2. (a) Discuss and compare various methods of electric braking. (10) (b) A $500\text{ V}$ d.c. shunt motor having an efficiency of $85\%$ operates a hoist having an efficiency of $70\%$. Calculate the current taken from the supply in order to raise a load of $500\text{ kg}$, at $3\text{ m/s}$. If rheostatic braking is employed, what resistance must be put in the armature circuit in order to lower the load at the same speed. (10) [20 marks]
- Q3. (a) Define the term coefficient of adhesion and explain the factors on which it depends. (10) (b) Explain the principle of series-parallel connection phenomenon of d.c. series motor in case of transition system. (10) [20 marks]
- Q4. State with reasons the criteria for selection of a motor for : (20) (a) Electric locomotive (b) Mining industry (c) Conveyor (d) Washing machine. [20 marks]
Section-B
- Q5. (a) Describe one method of measuring brightness of a source. (10) (b) Discuss laws of illumination and its limitations in actual practice. (10) [20 marks]
- Q6. (a) Describe different methods of resistance welding. (10) (b) A low frequency induction furnace operating at $10\text{ volts}$ in the secondary circuit takes $500\text{ kW}$ at $0.5\text{ p.f.}$ when the hearth is full. If the secondary voltage be maintained at $10\text{ volts}$, estimate the power observed and the power factor when the hearth is half-full. Assume the resistance of the secondary circuit to be thereby doubled and the reactance to remain the same. (10) [20 marks]
- Q7. Write short notes on the following : (a) Dielectric heating. (7) (b) Fluorescent lamp. (7) (c) Resistance heating. (6) [20 marks]
- Q8. (a) Describe the Ajax Wyatt (Vertical core) type induction furnace and explain its working. (10) (b) A $40\text{ kW}$, $3$-phase, $400\text{ V}$, resistance oven to employ nichrome strip $0.25\text{ mm}$ thick for the three star-connected heating elements. If the wire temperature is to be $1200^\circ\text{C}$ and that of the charge is to be $800\text{ }^\circ\text{C}$, estimate a suitable width of the strip. Assume emissivity $= 0.9$ and radiating efficiency $= 0.5$. Also determine the temperature of the wire when the charge is cold. The specific resistance of the nichrome-alloy is $1.3 \times 10^{-6}\text{ ohm-m}$. (10) [20 marks]