electrical circuits

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					                               [EURCS 406/EURIT 406]
                    B.Tech. DEGREE EXAMINATION
                                      IV SEMESTER
                             ELECTRICAL CIRCUITS
                  (Effective from the admitted batch 2007–08 onwards)
                            (Common for CSE & IT branches)
Time: 3 Hours                                                                    Max.Marks: 60
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Instructions: Each Unit carries 12 marks.
                    Answer all units choosing one question from each unit.
                    All parts of the unit must be answered in one place only.
                    Figures in the right hand margin indicate marks allotted.
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1. a) A linear network produces an output open circuit voltage of
      100V and an output chart circuit amount of 10A. Draw its
      Thevenin’s and Norton’s equivalents.                                                         6
   b) Using KCL find the potential at node A:                                                      6

                       sorry no diagram from our college itself

2. a) Use superposition theorem to find the current I 3 in terms of
          I1 , I 2 and R.                                                                          6
   b) Solve the above problem (2a) using Norton’s theorem OR
      Thevenin’s theorem.                                                6
3. a) Explain different types of armature windings in a dc machine.      8
   b) Explain winding factor.                                            4
4. a) Derive the cmf equation and torque equation of a dc motor          6
   b) Explain armature control and field control characteristics of a
      separately excited dc motor.                                       6
5. Explain `j’ notation for sinusoidal steady state quantities. Find
   the magnitude and phase ample of the current in a series RCC
   Circuit consisting of
    R  100, X 2  j 2  , X c   j 
    Draw the phasor diagram.                                            12
6. Draw the phasor diagram for the following circuit showing all
   currents and voltages. The phase sequence is RyB, VRN = 1o          12


7. Explain working of a transformer, with phasor diagram on load
   and on no load.                                                      12
8. Explain equivalent circuit of a single phase transformer and how
   it can be used for impedance transformation.                         12
9. Derive expressions for torque, rotor current and ship loss in a 3Q
   Induction motor from the equivalent circuit at constant v and f .     12
10. Explain various methods of starting induction motors. State
    advantages and disadvantages of the two types of 3Q induction
    motors.                                                              12


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