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Code No: C1EC03-C1406 I B.Tech(CCC) Supplementary Examinations, May/June 2007 NETWORK THEORY AND TRANSMISSION LINES (Electronics & Communication Engineering) Time: 3 hours
Max Marks:100 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆
1. (a) Explain i. ii. iii. iv.
KCL KVL Practical current source Practical voltage source.
(b) A 20V battery with an internal resistance of 5 ohms is connected to a resistor of x ohms. If an additional resistance of 6Ω is connected across the battery, find the value of x, so that the external power supplied by the battery remain the same. [10+10] 2. (a) Define the following: i. RMS value ii. Average Value and iii. Form factor of an alternating quantity. (b) A series circuit consisting of a 10 ohm resistor, a 100 µF capacitance and a 10mH inductance is driven by a 50Hz a.c. voltage source of max. value 100 volts. Calculate the equivalent impedance, current in the circuit, the power factor and power dissipated in the circuit. Also, draw the vector diagram. [8+12] 3. (a) Explain the procedure adopted to find the dual of a network. (b) Using the nodal analysis, find the node voltage, V1 and V2 in the circuit shown in figure 1. [6+10]
Figure 1:
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Code No: C1EC03-C1406 4. (a) State and explain Thevenin’s theorem.
[3+5]
(b) Estimate the power loss in the 8Ω resistor using Thevenin’s theorem. as shown in figure 2 [12]
Figure 2: 5. (a) A direct voltage of 200V is suddenly applied to series RL circuit having R = 20Ω and inductance 0.2H. Determine the voltage drop across the inductor at the instance of switching on and at 0.03 sec later. (b) A constant voltage of 100V is applied at t = 0 to a series RC circuit having R = 5MΩ and C = 20 µ F. Assuming no initial charge to the capacitor, find expression for i, voltage across R and C. [9+11] 6. Determine the transmission parameters of the network shown in figure 3.
[20]
Figure 3: 7. (a) Define the i/p impedance of a transmission line and derive the expression for it. [10] (b) The characteristic impedance of a certain line is 710 |14 0 Ω and γ = 0.007 + j0.028 per km. The line is terminated in a 300 Ω resistor. Calculate the i/p impedance of the line if its length is 100 km. [10] 8. (a) Explain the principle of Impedance matching with Quarter wave Transformer? [10] (b) A 100 Ω loss less line connects a signal of 100 KHz to a load of 140 Ω. The load power is 100mW . Calculate [10] i. Voltage Reflection coefficient, 2 of 3
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Code No: C1EC03-C1406 ii. VSWR, iii. Position of VM ax , IM ax Vmin and Imin. . Using smith chart. ⋆⋆⋆⋆⋆
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