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- Basic Electrical Engineering - BEE
- 2018
- PYQ
**Biju Patnaik University of Technology Rourkela Odisha - BPUT**- Electronics and Communication Engineering
- B.Tech
**6328 Views**- 221 Offline Downloads
- Uploaded 1 year ago

Registration No : Total Number of Pages : 03 B.Tech. 15BE2102 2nd Semester Back Examination 2017-18 BASIC ELECTRICAL ENGINEERING BRANCH : AEIE, AERO, AUTO, BIOMED, BIOTECH, CHEM, CIVIL, CSE, ECE, EEE, EIE, ELECTRICAL, ENV, ETC, FASHION, FAT, IEE, IT, ITE, MANUFAC, MANUTECH, MARINE, MECH, METTA, METTAMIN, MINERAL, MINING, MME, PE, PLASTIC, TEXTILE Time : 3 Hours Max Marks : 100 Q.CODE : C921 Answer Part-A which is compulsory and any four from Part-B. The figures in the right hand margin indicate marks. Answer all parts of a question at a place. Q1 a) b) c) d) e) f) g) h) i) j) Part – A (Answer all the questions) Answer the following questions: multiple type or dash fill up type What is the relation between time period T and frequency? i) T = 1 / frequency. ii) T = 0.5 / frequency. iii) T = 0.85 / frequency. iv) T = frequency. Resistivity of a conductor depends on _______ and _______. An electrolytic capacitor can be used for i) DC only. ii) AC only. iii) both A and B. iv) none Of the above. While comparing magnetic field and electric circuits, the point of dissimilarity exists while considering i) mmf and emf. ii) reluctance and resistance. iii) flux and current flow. iv) permeance and conductance. A motor having a power factor of 0.8 absorbs in active power of 1200 W the reactive power drawn from the supply is _________ VA. i) 130 ii) 900 iii) 250 iv) 400 If field current is decreased in shunt dc motor, the speed of the motor i) remains same. ii) increases. iii) decreases. iv) none of the above. In DC generators brushes are used for i) collecting of current without any sparkings ii) collecting of voltage iii) reduce eddy current loss iv) convert ac armature current in to dc Transformer core is made with laminated steel sheets in order to i) Increase eddy current loss ii) decrease hysteresis loss iii) Decrease eddy current loss iv) decrease copper loss. Series generators are used in which of the following applications? i) air crafts ii) arc welding iii) used as boosters in dc distribution or transmission iv) all of the above How many coulombs of charge flow through a circuit carrying a current of 10 A in 1 minute? i) 10 ii) 60 iii) 600 iv) 1200 (2 x 10)

Q2 a) b) c) d) e) f) g) h) i) j) Q3 a) b) Q4 a) Q6 Part – B (Answer any four questions) A 20V battery with an internal resistance of 5Ωis connected to a resistor of x ohms. If an additional 6Ωresistor is connected across the battery, find the value of x so that the external power supplied by the battery remains thesame. Explain the principle of operation of dc motor. (2 x 10) (10) (5) A coil of resistance 10Ω and inductance 0.1 H is connected in series with a 150 µF capacitor across a 200 V, 50 Hz supply. Calculate the voltage across the coil and the capacitor respectively. State and explain Kirchoff’s current law and Kirchoff’s voltage law. (10) (10) b) Three similar coils each having resistance of 10 Ohms and reactance of 8 Ohm are connected in star, across 400 V, 3 phase supply. Determine (i) line current, (ii) total power, (iii) reading ofeach of two wattmeter connected to measure power. Explain the working principle of a 3 phase induction motor. a) Calculate the supply voltage V in the circuit shown. (10) b) If a 6 pole induction motor supplied from a three phase 50 Hz supply has a rotor frequency2.3 Hz, calculate (i) the percentage slip, (ii) the speed of the motor. (5) b) Q5 Answer the following questions: Short answer type: What are the fundamental difference between e.m.f and potential difference? What will be the problem, if a capacitor directly connected to DC source? Why does the kinetic energy of a charged particle moving in a magnetic field remain constant? In a series RLC circuit, is it possible to achieve series resonance without changing the supply frequency. Justify your answer. What do you mean by phase sequence? How can the phase sequence be reversed? Why should an ammeter have low resistance? Which DC motor have more field resistance and why? What is the objective of Thevenin’s theorem? How thevenin’s voltage is calculated. Why iron core transformers are not used for high frequency applications? What do you mean by A/D and signal conditioning? a) (5) (5)

Q7 Q8 a) The maximum efficiency at full load and Upf of a single phase, 25 kV A, 500/1000 V, 50 Hztransformer is 98%. Determine the efficiency at (i) 75% load 0.9 pf, (ii) 50% load 0.8 pf,(iii) 25% load 0.6 pf (10) b) A coil consists of 600 turns and a current of 10 A in the coil gives rise to a magnetic flux of1 mWb. Calculate: (i) self inductance, (ii) The emf induced, (iii) The energy stored when acurrent s reversed in 0.01 sec. (5) a) Two impedances Z1 =(10 + j15)Ω and Z2 = ( 6- j8)Ω are connected in parallel. If the totalcurrent supplied is 15A, what is power taken by each branch? Define slip. Derive an expression for frequency of rotor current. (10) An induction furnace load requires 400 KW and 800 KV AR at 11KV (single phase), 50 Hz, Find: i) Power factor or pf angle ii) Current iii) Value of apparent power. Explain pipe earthing with neat diagram. Explain the physical phenomena of saturation in magnetic material. (6) b) Q9 a) b) c) (5) (4) (5)

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