MU Electronics Engineering (Semester 3)
Circuit Theory
December 2015
Total marks: --
Total time: --
INSTRUCTIONS
(1) Assume appropriate data and state your reasons
(2) Marks are given to the right of every question
(3) Draw neat diagrams wherever necessary


1 (a) The constants of a transmission lines are R=6/km, L=2.2mH/km
G=0.25×10-6 mho/km C=0.005×10-5 F/km
Determine the characteristic impedance propagation constant phase constant and attenuation constant at 1 KHz.
5 M
1 (b) Obtain the expression for i(t) if switch is closed at t=0 If v(t) is i(t) = ramp signal

5 M
1 (c) Check whether the polynomial is Hurwitz or not by continued fraction method. F(S)=S4+S3+4S2+2S+3.
5 M
1 (d) Find out V2V1 for the following n/w given below.

5 M

2 (a) Find the voltage across 5Ω resistor in the network shown below. If K=0.8 is coefficient of coupling.

8 M
2 (b) In the circuit shown, find out the expression for voltage V(t) across capacitor for t>0 At t=0 Switch is closed.

8 M
2 (c) Define ABCD parameters for the two port network hence obtain condition for symmetry.
4 M

3 (a) Find i, didt and d2idt2 at t=0+ in the circuit given below. Switch is changed from position 1 to 2 at t=0.

6 M
3 (b) Compare and Obtain Foster I and Foster II of the following RC impedance function. Z(S)=2(S+2)(S+4)(S+1)(S+3)
8 M
3 (c) Obtain Cauer form I of LC network Z(s)=(s2+4)(s2+16)s(s2+9)
6 M

4 (a) Derive the characteristic equation of a transmission line also obtain α β γ of the transmission line.
8 M
4 (b) Derive the relation for nominal impedance and cut off frequency for a constant k low pass filter.
4 M
4 (c) A network and its pole zero diagram are shown in fig. Determine the values of R, , C if Z(0)=1.

8 M

5 (a) Check whether the following functions are PRF or not i) F(s)=S(S+3)(S+5)(S+1)(S+4)ii) F(S)=S3+6S2+7S+3S2+2S+1
8 M
5 (b) Find the current Ix using superposition theorem.

6 M
5 (c) The current I(S)=2S(S+1)(S+2) plot the pole zero pattern in s-plane hence obtain i(t) by finding out residues by graphical method.
6 M

6 (a) The characteristics impedance of a high frequency line is 100Ω. If it is terminated by a load impedance of 100 +j100Ω. Using smith chart find out (i) VSWR
(ii) Refection coefficient (iii) Impedance at 110 of wavelength away from load (iv) VSWR minimum and VSWR maximum away from the load.
8 M
6 (b) For the network shown and find out v1I1 and v2I1

6 M
6 (c) Find out Thevenin's equivalent network.

6 M



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