AMIETE – ET (OLD SCHEME)

 

Code: AE08                                                                  Subject: CIRCUIT THEORY & DESIGN

Flowchart: Alternate Process: JUNE 2010Time: 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 the best alternative in the following:                                  (210)

      

       a. The current through 2 register in the Fig.1 is:

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                   (A) 3                                                   (B) 2

(C)  1                                                   (D) 0

 

b. Time constant of a capacitance circuit may be defined as the time during which voltage

 

(A)     rises to 63.2% of its final steady value                                                                      

(B)   rises to 38.6% of its final steady value

(C)  falls to 38.6% of its final steady value                                                                        

(D)  50% of its final steady state value.

 

c.  A capacitor used in 240 volt AC line should have a peak voltage rating of

 

(A)  240 volts                                      (B) 340 volts

(C)  120 volts                                      (D) 720 volts

 

             d.   If four resistors each of 4 k are connected in parallel, the net resistance is

 

(A)    1 k                                         (B) 16 k

(C)  2 k                                          (D) 8 k

 

             e.   In the circuit VS = 10 cost, power drawn by the 2 ohm resistor in 4 watt. The power factor is 

                  

(A)     0.3                                               (B) 0.4

(C)  0.6                                               (D) 0.8

 

             f.    Kirchoff’s voltage law cannot be used

                                                                                               

                   (A)  with parallel circuit                       

                   (B)  to find current in a circuit

(C)  to find voltage across a resistor in a series circuit                                                       

(D)  for non-linear circuits

            

             g.   In RLC circuit, the current at resonance is

 

(A)     maximum in parallel resonance and minimum in series resonance.                      (B)     maximum in series resonance and minimum in parallel resonance.

(C)  maximum in both series and parallel resonance.                   

                   (D)  minimum in both series and parallel resonance.

 

             h.    The current in the 12  resistor in the following circuit (Fig.2) is given by
 
 


                   

 

 

 

 

 

 

 

                                                                                  

                    (A) 10 amp from left to right               (B) 10 amp from right to left

  (C)  5 amp from left to right               (D) 5 amp from right to left

 

             i.    If the load connected to the source is inductive, for a maximum transfer of power from source to load, the source impedance should be

              

(A)   Inductive                                      (B) capacitive

(C) Resistive                                        (D) combination of L and C

 

 

             j.    Kirchoff’s current law is valid for

                  

(A)    DC circuits only                            (B) AC circuits only

(C) Both DC and AC circuits               (D) Sinusoidal sources only

  

 

Answer any FIVE Questions out of EIGHT Questions.

Each question carries 16 marks.

 

  Q.2     a.   Explain Duality and find dual of the given network (Fig.3).                              (3+3)

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              b.   Determine Ix and Iy in the Fig. 4, using Kirchoff’s law.                                         (5)

 

                          c.    For the circuit Fig. 5, find VBG using Nodal analysis.                                           (5)
 
 

 

 

 

 

 

 


                  

Q.3       a.   What do you mean by Initial conditions?                                                         (4+4)

                   Switch ‘S’ in the circuit shown in Fig. 6 below is closed at t=0.

                   Determine the initial value of i, di/dt and d2i/dt2
 
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              b.   In the network shown in Fig.7, initial voltage on C1 is V1 and on C2 is V2,         such that V1 (0)=V1 and V2 (0)=V2. The switch ‘K’ is closed at t=0. Obtain i(t) and V2(t) for all time. Given Data: ,F, F,  and.                                                                (8)

 

    Q.4   a.   Define poles and zeros of a network function.          Find the transfer function of the

                   network shown in the Fig. 8. Also sketch pole zero configuration.                   (2+6)
 
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             b    State Thevenin’s theorem. Find the power loss in the 2 resistor shown in Fig. 9 using Thevenin’s theorem.                                                         (2+6)

 

Q.5       a.   Find Z parameters of the network shown in the Fig.10.                                       (8)
 
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             b.   Derive the expressions for O/P voltage, O/P current and amplification factor of single tuned circuit shown in Fig. 11 at resonance.                           (8)

 

Q.6       a.   Show that an average power consumed by inductor circuit is Zero.                     (4)

                                                                                                                                                

b.   Find the resultant of three currents and express it in the form

      of                                                                                                                      (6)

 

                 

 

             c.   Determine the form factor of the given waveform (Fig.12).                                  (6)
 
 

 

 

 

 

 

 

 

 

 

 


Q.7       a.   Diagnose whether the following impedance function represents a RL or RC network and find its first Cauer Form Z(s)= [(s+4)(s+6) / (s+3)(s+5)]  (8)

             b.   Test whether the polynomial  is Hurwitz or not.                                 (4)

             c.   Check the positive realness of the function          (4)                                                                                                                                                                            (iii) Calculate the voltages across the capacitor and the coil.                                                           (8)

 

Q.8       a.   Design a constant K-low pass filter having fc=2 kHz and design impedance Ro=600. Obtain the value of attenuation at 4 kHz.                            (8)

 

             b.   Find the short-circuit admittance functionand for the network in the Fig.13.                     (8)

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  Q.9            a.  Find the current i(t) for the network shown in Fig.14, when the voltage source         

                         is                                                      (8)

            

              b. Find the current through the capacitor of ( 5)  reactance shown in   Fig.15 below, using superposition theorem.                                              (8)