R09 - December, 2011 - Regular Examinations - Set - 4.

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) If the current waveform shown in below Figure.2 is applied to a 5 micro-farads capacitor, find the capacitor voltage vc(t) and prepare a sketch showing this waveform. Assume that the initial capacitor voltage is zero. [5 10]
Figure.2
2. Obtain the equivalent resistance Rab for the circuit shown in below Figure.3. Find the current i for the input voltage of 140 V and calculate the current in all the elements of the circuit. [15]
Figure.3
3.a) A resultant current wave is made up of two components : a 5A D.C component and a AC component of 50 Hz sinusoidal waveform which has a maximum value of 5A.
i) Sketch the resultant wave

ii) Write an analytical expression for the current wave and find a point where the AC
component is zero value and also find where di/dt is positive.
iii) What is the average value of the resultant current over a cycle?
iv) What is the effective value of the resultant current?
b) In a RC series circuit, which element doesnot consumes power? and prove it. [10 5]
4.a) For the parallel resonant circuit shown in below Figure.4 with Rs= 8 O.
Figure.4
i) Determine resonant frequency (fs), half power points.
ii) Calculate the maximum impedance and the magnitude of the voltage VC at fm.
iii) Determine the quality factor Qp.
iv) Calculate the bandwidth.
b) A non inductive resistance R, variable between 0 and 12 ohms, is connected in series with a coil of resistance of 4 ohms and reactance of 5 ohms the circuit supplied from a 230 V a,c supply. By means of a locus diagram, determine the current supplied to the circuit when R is 0, 6 and 12 ohms. [10 5]
5. Define the coefficient of coupling and Calculate the power supplied to the 10 ohms resistor in the ideal transformer circuit shown in the below Figure.5. [15]
Figure.5
6. With the help of suitable example explain about the concept of super-mesh. Solve for Io in the circuit as shown in below Figure.6 using mesh analysis. [15]
Figure.6

7. State Tellegen’s, Reciprocity theorems. For the circuit below Figure.7, find the Thevenin’s equivalent between terminals a and b. [15]
Figure.7
8. Using Thevenin’s theorem, find vo in the circuit shown in below Figure.8. [15]
Figure.8
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