Code: DE07                                             Subject: NETWORK AND TRANSMISSION LINES

Time: 3 Hours                                                                                                     Max. Marks: 100

NOTE: There are 9 Questions in all.

· Question 1 is compulsory and carries 20 marks. Answer to Q. 1. must be written in the space provided for it in the answer book supplied and nowhere else.

· Out of the remaining EIGHT Questions answer any FIVE Questions. Each question carries 16 marks.

· Any required data not explicitly given, may be suitably assumed and stated.

Q.1       Choose the correct or best alternative in the following:                                         (2x10)

             a.  If , then i(t) is

(A) (B)

(C) (D)

             b.  A practical constant voltage source is:

(A) Zener                                             (B)  Pentode

(C) FET                                               (D) Transistor

             c.  Thevenin’s theorem is valid for a network containing only:

(A) Linear elements                              (B)  Non linear elements

(C) Reactive elements                           (D) Resistances

             d.  In Z – parameters representation if Z₂₁ = Z₁₂ then the network is:

(A) Bi - lateral                                      (B) Symmetrical 

(C) Balanced                                        (D) Inverse

             e.  An attenuator is an:

(A) R’s only network                            (B)  RL network

(C) RC network                                   (D) LC network

             f.   In co-axial cables, radiation loss, in comparison to open wire line, is:

(A) Lower                                            (B) Higher

(C) Same                                             (D) None of the above

             g.  Z_o of  line depends on:

(A) Value of Z_L (B) Length of line

(C) Frequency of signal                         (D) Strength of input voltage

             h.  Cut-off frequencies of constant K filters of all types are given by:

(A) Z₁/4Z₂ = 0                                      (B) Z₁/4Z₂ = 1

(C) Z₁/4Z₂ = –1                                    (D) None of the above

             i.   In a series resonant circuit, the impedance of the circuit:

(A) Minimum                                        (B) Maximum 

(C) Selectivity                                       (D) None of the above

             j.   Higher the Q of a series circuit:

(A) Sharper its resonance                     (B) Greater its bandwidth

(C) Broader its resonance curve            (D) Narrow its pass band

Answer any FIVE Questions out of EIGHT Questions.

Each question carries 16 marks.

  Q.2     a.   Distinguish between:                                                                                           (6)

                   (i) Active & Passive elements.

                   (ii) Linear & Non-linear elements.

             b.   A capacitor of 5 μF stores 2.5 x 10^–2 J of energy. Determine:                              (8)

                   (i)  Amount of charge stored.            (ii) Voltage across the capacitor

c. A delta connection contains 3 impedances of 30 each. Obtain impedances of the equivalent star connection.                                          (2)

  Q.3     a.   State & prove initial and final value theorem.                                                       (6)

            b.   In two mesh network, obtain the expression for I₁(s) & I₂(s) when the switch is closed.                   (6)

             c.   Find the Laplace transform of the following:                                                        (4)

                   (i)  f(t) = t sin 2t.

                   (ii) An impulse function is given by δ (t – t1)

Q.4     a.   Determine the Z – parameters for the following circuit:                                        (6)

             b.   Find the driving point impedance for the network:                                               (6)

             c.   Explain Y parameters & also draw its equivalent circuit representation.                (4)

  Q.5     a.   State & Prove compensation theorem.     (8)

             b.   Find the current in resistor 3  & Voltage across it.                                           (8)

Q.6     a.   In given circuit the switch S is kept first at position 1 & steady state condition is reached. At t = 0, the switch is moved to position 2. Find the current in both cases.                                                        (8)

             b.   What do you understand by steady state? Carry out the sinusoidal steady state analysis of a parallel RL network if the network is excited by a source . (8)

Q.7     a.   Define the concept of selectivity & BW and also derive their values in terms of Q & ω_o.                  (8)

             b.   Obtain the values of R,L,C in series RLC circuit that resonates at 6 KHz &                  consumes 500 W from a 50 V a.c. source operating at the resonance frequency. The bandwidth is 0.75 KHz.            (8)

  Q.8     a.   Write short notes on the following:                                                                      (8)

                   (i)  Reflection in open & short circuited lines.

                   (ii) Characteristic impedance

                   (iii) Lossless Line

                   (iv) Primary and secondary constants of Transmission Line

             b.   A transmission line has the following constants:                                                    (4)

                   R = 10.4, L = 3.666mH, C = 0.00835 μ F  & G = 0.08 μ mhos. Calculate

                   Z_o & Vp (phase velocity) at   = 5000 rad/sec

            c.   Differentiate between T section and Network with the help of suitable diagram. (4)

  Q.9     a.   Explain filter and its types in detail.                                                                      (6)

             b    Describe the classification of attenuators. Design a symmetrical bridged-T attenuator to provide attenuation of 40 dB and to work into a line of characteristic impedance of 600.                              (10)