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Circuits and Networks : Question Paper May 2015 - Electronics & Telecomm (Semester 3) | Gujarat Technological University (GTU)

## Circuits and Networks - May 2015

### Electronics and Comm. Engg. (Semester 3)

TOTAL MARKS: 100
TOTAL TIME: 3 HOURS
(1) Question 1 is compulsory.
(2) Attempt any four from the remaining questions.
(3) Assume data wherever required.
(4) Figures to the right indicate full marks.
1 (a) Explain the terms: (i) Linear (ii) Bilateral (iii) Passive (iv) Reciprocal (v) Time invariant (vi) Oriented graph and (vii) Tree.(7 marks) 1 (b) Justify: the current in an inductor and voltage across a capacitor cannot change instantaneously.(7 marks) 2 (a) State and explain maximum power transfer theorem. Also derive the condition for maximum power transfer to the load for DC and AC circuit.(7 marks)

### Answer any one question from Q2 (b) & Q2 (c)

2 (b) Using mesh analysis determine mesh current i and the value of k which causes i=0 if V1 =10 v and V2=2 v for the network shown in figure 1. (7 marks) 2 (c) Using nodal analysis find the value of k such that V y is zero for the network shown in figure 2. (7 marks)

### Answer any two question from Q3 (a), (b) & Q3 (c), (d)

3 (a) What is significance of initial condition? Write initial conditions for R, L and C at t=0 + and at t=∞.(7 marks) 3 (b) For the network shown in figure 3 the switch k is closed at t=0, also it reaches a steady state with the switch k open. Find the current i(t) for all time. (7 marks) 3 (c) What is time constant? Explain time constant in terms of RL and RC circuit.(7 marks) 3 (d) Determine Vb (0+) and Vb (∞) for the network shown in figure 4, which reaches to steady state with switch k open and at t=0, the switch k is closed. (7 marks)

### Answer any two question from Q4 (a), (b) & Q4 (c), (b)

4 (a) Explain concept of poles and zeros and their significance in network functions.(7 marks) 4 (b) Find the h parameters for the network shown in figure 5. (7 marks) 4 (c) Find Laplace transform of f1(t)=cos ωt and f2(t)=e-at sin ωt.(7 marks) 4 (d) For the network shown in figure 6 determine voltage transfer gain G12 =V2/V1. (7 marks)

### Answer any two question from Q5(a), (b) & Q5 (c), (d)

5 (a) Derive relationship between incidence matrix (A), fundamental cut-set matrix (Qf) and fundamental tie-set matrix (Bf).(7 marks) 5 (b) Find the Z parameters for the network shown in figure 7. (7 marks) 5 (c) Derive expression of h parameter in terms of Z and Y parameters.(7 marks) 5 (d) For the network shown in figure 8 draw the oriented graph. Also obtain incidence matrix (A), fundamental tie-set matrix (Bf) and fundamental cut-set matrix (Qf). (7 marks)

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