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Sunday, 2 October 2016

Basic electrical Engineering-Model question paper for B.E/B.Tech

1(a) Mention the limitations of Ohm’s law. (04 Marks)
(b) What are ideal voltage source and ideal current source? (04 Marks)
(c) State and explain Kirchoff’s voltage law and current law. (08 Marks)
(d) Two voltmeters A and B having resistances 25 kΩ and 15 kΩ respectively are connected in series across 240V. What is the reading of each voltmeter? (04 Marks)
2(a) Give the expression for mutual inductance between two coils connected on same magnetic material. Explain the terms. (04 Marks)
(b) Explain Fleming’s right hand rule and left hand rule. (06 Marks)
(c) Derive an expression for dynamically induced E.M.F. (06 Marks)
(d) A coil of 300 turns wound on a non-magnetic material has an inductance of 10 mH. Calculate (a) the flux produced by a current of 5A and (b) the average value of the e.m.f induced when a current of 5A is reversed in 8ms.(04 Marks)
3(a) What is a D.C shunt generator? Draw its circuit and explain. (06 Marks)
(b) Explain the terms back pitch, front pitch and resultant pitch. (06 Marks)
(c) What is the function of brushes? What material is used to make brushes? (04 Marks)
(d) A 4 pole generator with wave wound armature has 51 slots, each having 24 conductors; the flux per pole is 0.01 Weber. At what speed must the armature rotate to give an induced e.m.f of 220 V? What will be the voltage developed, if the winding is lap connected and the armature rotates at the same speed developed? (04 Marks)
4(a) What is the need for using starters in DC motors? (03 Marks)
(b) Mention some applications of DC cumulatively compounded motor. (04 Marks)
(c) Explain in detail different characteristics of DC shunt motors. (09 Marks)
(d) The armature current of a series motor is 60A, when on full load. If the load is adjusted so that this current decreases to 40A, find the new torque expensed as a percentage of full torque. The flux for a current of 40A is 70% of that when the current is 60A. (04 Marks)
5(a) With a neat figure, explain the construction and working principle of a dynamometer type watt meter. (08 Marks)
(b) Whar are the advantages of sinusoidal waveform generation? (04 Marks)
(c) Write a note on the significance of power factor. (04 Marks)
(d) A coil of power factor 0.6 is in series with a 100 µF capacitor. When connected to a 50 Hz supply, the potential difference across the coil is equal to the potential difference across the capacitor. Find the resistance and inductance of the coil. (04 Marks)
6(a) What are the various types of domestic wiring? (04 Marks)
(b) With neat figures, explain casing and capping. (06 Marks)
(c) What is an earth leakage circuit breaker? Mention the different types of ELCB’s. (06 Marks)
(d) Define fusing current and fusing factor. (04 Marks)
7(a) What is phase sequence and what is its significance. (04 Marks)
(b) Define three phase AC circuits. Explain the generation of three phase voltage. (06 Marks)
(c) Explain the terms pitch factor, distribution factor and winding factor as applied to an alternator. (06 Marks)
(d) A 2 pole, 3 phase alternator running at 3000 r.p.m has 42 armature slots with 2 conductors in each slot. Calculate the flux per pole required to generate a line voltage of 2300 V. Distribution factor is 0.952 and the pitch factor is 0.956. (04 Marks)
8(a) Derive the e.m.f equation of a transformer. (06 Marks)
(b) Derive the condition for which the efficiency of a transformer is maximum. (06 Marks)
(c)  Explain the working principle of a three phase induction motor. (04 Marks)
(d) A 100 KVA, 50 Hz single-phase transformer has a turn ratio of 1000/250. The primary winding is connected to 500V, 50 Hz supply. Find the secondary open circuit voltage and the maximum value of the flux in the core. (04 Marks)

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