R09 - December, 2011 - Regular Examinations - Set - 3.

B.Tech II Year - I Semester Examinations, December 2011
ELECTRICAL CIRCUITS
(COMMON TO EEE, ECE, ETM)
Time: 3 hours Max. Marks: 75
Answer any five questions
All questions carry equal marks
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1.a) Calculate the power supplied or absorbed by each element as shown in below Figure.1.
Figure.1
b) A series RLC circuit with R= 4 ohms, L = 2mH and C = 500 micro-farads is carrying a current waveform shown in below Figure.2. Find the voltage across each element and sketch each voltage to same time scale. [5 10]
Figure.2
2. A network is arranged as shown in below Figure.3, and a battery having an e.m.f. of 10 V and negligible internal resistance is connected across the terminals AC. Determine the value and direction of the current in each branch of the circuit. [15]
Figure.3

3.a) Prove that if a D.C current of Iamps is superposed in a conductor by an A.C current of maximum value I amps, the r.m.s value of the resultant is 23I.
b) For the parallel circuit shown in below Figure.4 has the parameter values as: R1 = 100 ohms ( non inductive) ; coil Rc = 40 ohms, Lc = 0.52 H, R2 = 120 ohms; and Xc = 158 ohms (at 50 Hz).
i) Determine the branch currents and the total current
ii) Draw the phasor diagram indicating the curerents and voltages across the coil
and capacitor.
iii) If the A.C source is replaced by an equivalent D.C source, what current wound be
drawn by the circuit? [5 10]
Figure.4
4.a) Derive an expression for the resonant frequency for a parallel circuit shown in below Figure.5.
Figure.5
b) Draw the locus diagram and obtain the value of RL in the circuit shown in below Figure.6 which results in resonance for the circuit. [7 8]
Figure.6
5.a) Consider the circuit shown in below Figure.7. Determine the coupling coefficient. Calculate the energy stored in the coupled inductors at time t = 1s if v = 60 cos(4t 30?)V.

Figure.7
b) For the circuit shown in below Figure.8, calculate the input impedance and current I1.
Consider [10 5] 1260100, 3040, 8060LZjZjandZj=-O= O= O
Figure.8
6. With the help of suitable example explain about the concept of super-node. For the circuit shown in below Figure.9. Find Vo in the circuit using node analysis. [15]
Figure.9
7. State Millman’s and Compensation theorems for d.c excitations. Apply the superposition principle to find vo in the circuit shown in below Figure.10. [15]
Figure.10
8. Obtain current Io inFigure.11 shown below using Norton’s theorem. [15]
Figure.11
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