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I B.Tech Semester Supplimentary Examinations, June 2009 NETWORK THEORY ( Common to Electrical & Electronic Engineering, Electronics & Communication Engineering, Computer Science & Engineering, Electronics & Instrumentation Engineering, Bio-Medical Engineering, Information Technology, Electronics & Control Engineering, Computer Science & Systems Engineering, Electronics & Telematics, Electronics & Computer Engineering and Instrumentation & Control Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆ ⋆ ⋆ ⋆ ⋆
- (a) Distinguish between dependent sources and independent sources. Give some examples. (b) Find V 1 in figure1b
Figure 1b (c) Find Vx , r 2 , and r 3 in the figure1c. [4+6+6]
Figure 1c
- (a) Explain Faraday’s laws of electromagnetic induction. (b) A ring has a mean diameter of 21cm and a cross-sectional area of 10cm^2. The ring is made up of semicircular sections of cast iron and cast steel, with each joint having a reluctance equal to an airgap of 0.2mm. Find the ampere turns required to produce a flux of 8× 10 −^4 wb. The relative permeabilities of cast steel & cast iron are 800 & 166 respectively. Neglect fringing & leakage effects. [4+12]
- (a) Define RMS value, Average Value, form factor and peak factor. (b) Find the value of R 1 and X 1 when a lagging current in the circuit the following figure3b. Gives power of 2 K.W. [6+10]
Figure 3b
- (a) Explain how the current locus can be obtained for the following circuit shown in Figure 4a. with neat diagram.
Figure 4a (b) The voltage across the inductance in a series resonant circuit at resonance is obtained as 100V for an applied voltage of 10V. If the current at resonance is given by 10mA and Band width is 5K rad/sec find the i. resonance frequency ii. values of L and C. iii. half power frequencies. [6+10]
- (a) A 3 phase 3 wire balanced supply is connected to an unbalanced 3 wire star connected load. Derive an expression for the neutral displacement voltage between supply and load neutral points. (b) A 3phase, 3 wire 208 volts BYR system has a star connected load with ZR = 6^6 00 Ω ZY = 6^6 300 and ZB = 5^6 450. Obtain the line currents and load voltages of the circuit using the neutral displacement method. Draw the phasor diagram. [6+10]
- (a) Design an m – derived T – section High pass filter having cutoff frequency
fc = 4 kHz, and frequency of infinite attenuation at f∝ = 4.8 kHz, to fit into 600Ω line. (b) In the network shown in figure6b find current I using nodal analysis.
I B.Tech Semester Supplimentary Examinations, June 2009 NETWORK THEORY ( Common to Electrical & Electronic Engineering, Electronics & Communication Engineering, Computer Science & Engineering, Electronics & Instrumentation Engineering, Bio-Medical Engineering, Information Technology, Electronics & Control Engineering, Computer Science & Systems Engineering, Electronics & Telematics, Electronics & Computer Engineering and Instrumentation & Control Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆ ⋆ ⋆ ⋆ ⋆
- (a) Obtain the expressions for star-delta equivalence of resistive networks (b) Determine the voltage appearing across terminals y-z if a d.c. voltage of 100V is applied across x-y terminals in the figure1b. [6+10]
Figure 1b
- (a) Calculate the current to be passed through the coil so that a flux of 1 mwb is produced in the air gap. {As shown in the Figure2a}
Figure 2a The core is of square cross section over its entire length and has a permeability of 800.
(b) Define the following terms. i. Coefficient of coupling in coupled coils ii. Magnetic flux density. iii. Reluctance of magnetic path iv. Permeability. [8+8]
- (a) Define Reactance, suceptance, impedance and admittance.
(b) A voltage of 240V applied to a pure resistor, pure capacitor and an inductor in parallel. If the total current and the currents in the resistor, capacitor and inductor are respectively 2.3 A, 1.5A, 2A and 1.1A Find the over all power factor and the power factor of the inductor. [6+10]
- (a) The circuit shown in figure4a is resonant for two values of C when the fre- quency of the supply is 5000 rad/sec. Find the values of C and draw the admittance locus.
Figure 4a (b) Find the y-parameter of the two port network shown in figure4b.
Figure 4b [8+8]
- (a) A 3 phase 3 wire balanced supply is connected to an unbalanced 3 wire star connected load. Derive an expression for the neutral displacement voltage between supply and load neutral points.
(b) Verify the reciprocity theorem using the network given in the figure7b. [6+10]
Figure 7b
- (a) Derive the expression for V(t) of a parallel R – C circuit when excited by a sinusoidal current source (b) Find i (t) for t ≥ 0 in the following figure8b. [8+8]
Figure 8b
I B.Tech Semester Supplimentary Examinations, June 2009 NETWORK THEORY ( Common to Electrical & Electronic Engineering, Electronics & Communication Engineering, Computer Science & Engineering, Electronics & Instrumentation Engineering, Bio-Medical Engineering, Information Technology, Electronics & Control Engineering, Computer Science & Systems Engineering, Electronics & Telematics, Electronics & Computer Engineering and Instrumentation & Control Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆ ⋆ ⋆ ⋆ ⋆
- (a) State and explain KCL and KVL (b) Distinguish between i. independent and dependent sources ii. Ideal and practical sources. (c) Find Vs if r 1 = 2 Ω r 2 = 1 Ω r 3 = 5 Ω the following figure1c
Figure 1c [2+2+2+2+8]
- (a) Distinguish between Self induced EMF and Mutual induced EMF. (b) Draw the dotted equivalent for the circuit shown Figure2b explaining the procedure to identify the dotted ends.
Figure 2b (c) A rectangular core has a C.S. area of 20cm^2. It is made from two materials cast steel 50cm long and sheet steel 30 cm long. It is desired to create a flux of 2 milliwebers in the core. The relative permeability for cast steel is 1000 and that of sheet steel is 2000. The coil has 200 turns. Find the MMF and current in the coil. [4+4+8]
- (a) Define RMS value, Average Value, form factor and peak factor.
Figure 6a (b) Construct the incidence matrix for the graph shown in Figure 6b.
Figure 6b (c) Use nodal analysis, to determine the voltages V 1 and V 2 in the circuit shown the Figure 6c. [4+4+8]
Figure 6c
- (a) State and explain Millmann’s theorem.
(b) Using Millman’s theorem find the Neutral shift voltage Von the following network shown in figure7b. [6+10]
Figure 7b
- (a) Derive the expression for i(t) and voltage across capacitance Vc(t) for series R
- C circuit with D.C. voltage applied to it at t = 0. Explain about the time constant of RC circuit. (b) Switch S is moved from position 1 to 2 at t = 0 find the voltages VR(t) and Vc(t) for t≥0 the following figure8b. [8+8]
Figure 8b
(c) A circular iron ring having a C.S. area of 5cm^2 and a length of 4
cms in Iron has an air gap of 0.
cm made as a saw cut. The relative permeability of iron is 800. The ring is wound with a coil of 2000 turns and carries a current of 100mA. Determine the air gap flux. Neglect leakage and fringing. [4+4+8]
- (a) Find the RMS and average value of the waveform the following figure3a.
Figure 3a (b) If the circuit shown in figure 3b, the effective voltage across the parallel branch is 100V find the supply voltage Vs and power supplied by it. Draw the phasor diagram. [6+10]
Figure 3b
- (a) Obtain the y-parameters of the following figure4a bridged T- network.
Figure 4a (b) Obtain the expression for Y-parameter in terms of transmission parameters.
(c) For a series resonance circuit obtain the expression for band width in terms of resonance frequency and Q-factor. [6+6+4]
- (a) Derive the relationship between line and phase quantities in a balanced star connected system. (b) A 3phase 4-wire CBA system of phase sequence, with effective line voltage of 100v has a star-connected impedances given by ZA=3.0^6 00 Ω ZB = 4. 56 56. 310 Ω ZC = 2. 246 − 26. 570 Ω Obtain the line currents and current in neutral wire. Draw the phasor diagram. [6+10]
- (a) For the coupled network (shown in figure6a) write down the loop equations in matrix form.
Figure 6a (b) Using nodal Analysis, find the power supplied by 8V source the following figure6b.
Figure 6b (c) Derive the expressions for the elements of m-derived
filter in terms of pro- totype Π filter. [4+8+4]
- (a) State and explain Norton’s Theorem.
(b) Using Thevenin’s theorem find the power in 10 ohms resistor in the following network shown in figure7b. [6+10]
