The Institution of Engineers,India 2006 Diploma Electrical and Electronics NETWORK AND TRANSMISSION LINES - - Question Paper

Code: D-07   Subject: NETWORK AND TRANSMISSION LINES

Time: 3 Hours                                                      June 2006                                                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.       A line becomes distortionless if 

                   (A)  It is properly matched                   (B)  It is terminated into Zo

(C)    LG = CR                                     (D)  LR = GC

b.      Double stub matching eliminates standing waves on the

(A)    Source side of the left stub            (B)  Load side of the right stub

(C)  Both sides of the stub                   (D)  In between the two stubs

             c.   If  and , the characteristic impedance is

(A)    400                                          (B)  60

(C)  80                                            (D)  170

             d.   The final value of f (t) for a given  

(A)    Zero                                           (B) 

(C)                                               (D) 

             e.   If the given network is reciprocal, then according to the reciprocity theorem

(A)                                        (B) 

(C)                                      (D) 

             f.    The frequency of infinite attenuation  of a low pass m-derived section is

(A)     Equal to cut off frequency of the filter.     

(B)     .

(C)     Close to but greater than the of the filter.   

(D)    Close to but less than the of the filter.

             g.   The dynamic impedance of a parallel RLC circuit at resonance is

(A)                                              (B) 

(C)                                           (D) 

             h.   Laplace transform of the function is

(A)                                                (B)

(C)                                        (D) 2s.

             i.    A (3 + 4j) voltage source delivers a current of (4 + j5) A.  The power delivered by the source is

(A)   12 W                                           (B) 15 W

(C) 20 W                                            (D) 32 W

             j.    In a variable bridged T-attenuator, with  zero dB attenuation can be obtained if bridge arm  and shunt arm  are set as 

(A)                          (B)  

(C)                         (D) 

Answer any FIVE Questions out of EIGHT Questions.

Each question carries 16 marks.

  Q.2     a.   Using current to voltage transformation, find the current flowing through the resistor  as shown in Fig.1.                                                  (4)

             b.   A current of A flows in a capacitor of value C = 0.22.  Calculate the voltage, charge, and energy stored in the capacitor at time t =2 sec.                                                               (4)

             c.   Find the sinusoidal steady state solution  for a parallel RL circuit.                    (8)

  Q.3     a.   Find the Laplace transform of the functions:                                                            

                   (i)  .                                        (ii)  .                                           (4)

             b.   Find the convolution of  and  when  and .           (4)          

             c.   A unit impulse is applied as input to a series RL circuit with R =  and    L = 2H.  Calculate the current i(t) through the circuit at time t = 0.            (8)

  Q.4     a.   Define the image impedances of an asymmetric network.  Determine the image impedances of the L section shown in Fig.2.                                    (6)

             b.   Write short notes on:-                         

(i)                  Smith chart and its applications.

(ii)                Poles and zeros of a network function.                                      (10)

  Q.5     a.   State Nortons theorem and using Nortons theorem find the current flowing through the  resistor.                                                                  (2+6)

             b.   Find the current in resistor  of the network using Millmans theorem.              (8)

  Q.6     a.   Find the z parameters of the given network.  From the z parameters, find the h parameters equivalent and the ABCD parameters equivalent.

             (10)

             b.   Find the transform impedance Z(s) of the one port network.                                (6)

  Q.7     a.   Calculate the half power frequencies of a series resonant circuit whose resonant frequency is 150KHz and the band width is 75 KHz.  Derive the relations used.                                                         (10)   

             b.   The combined inductance of two coils connected in series is 0.6 H and    0.1 H depending on the relative directions of the currents in the coils.  If one of the coils, when isolated, has a self inductance of 0.2 H, calculate the mutual inductance and the coefficient of coupling.                            (6)

  Q.8     a.   A loss less line of characteristic impedance 500  is terminated in a pure resistance of 400.  Find the value of standing wave ratio.                (4)

             b.   Why is loading of lines required?  Explain the different methods of loading a line.                 (6)

                  c.   A loss less transmission line has an inductance of 1.5 mH/Km and a capacitance of 0.02 .  Calculate the characteristic impedance and phase constant of a transmission line.  Assume                                                             (6)                                                             

  Q.9     a.   Design a symmetrical bridge T attenuator with an attenuation of 40 dB and an impedance of 600 .                                                                     (8)

             b.   State and prove the theorem connecting the attenuation constant,  and characteristic impedance  of a filter.                                                    (4)

             c.   With the help of frequency response curves, give the classification of filters.                         (4)