JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II NETWORK THEORY Previous Question Paper (February - 2024 - R13)
Note: i) Question paper consists of Part A, Part B. ii) Part A is compulsory, which carries 25 marks. In Part A, answer all questions. iii) In Part B, Answer any one question from each unit. Each question carries 10 marks and may have a, b as sub questions.
PART - A
Write the expression for active power in a balanced 3 phase circuit?
Answer
The active power P in a balanced 3-phase circuit is given by the expression:
where VL is the line voltage, IL is the line current, and cos φ is the power factor of the load.
Draw the phasor diagram of balanced star connected system.
Answer
In a balanced star-connected system, the three phase voltages (VRN, VYN, VBN) are equal in magnitude and displaced by 120° from each other. The phasor diagram is constructed as follows:
- Draw three vectors of equal length separated by 120° representing the phase voltages VRN, VYN, and VBN.
- The line voltages are represented by the phasors VRY = VRN - VYN, VYB = VYN - VBN, and VBR = VBN - VRN.
- In the diagram, these line voltage phasors are drawn such that their magnitude is √3 times the phase voltage, and they lead their respective phase voltages by 30°.
The resulting diagram shows the phase voltages at 0°, -120°, and -240° (or +120°), with the line voltages positioned between them to maintain the balanced three-phase relationship.
Explain why the voltage across a capacitor cannot change instantaneously
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What are transients in electric circuits
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Explain any two necessary conditions for driving point functions.
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Define poles and zeros for a transfer function?
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The equations of a two-port network are: I1 = 10 V1 + 20 V2 and I2 = 5 V1 + 7V2. From the given equations, determine whether this 2-port network is symmetric and reciprocal or not.
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Express Y –parameters in terms of Z-parameters.
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What are the different types of filters?
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Explain i) line spectra and ii) phase angle spectra
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PART - B
Derive the formula for power factor in two wattmeter method.
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Three impedance each (5 +j12) ohm is connected in star are connected to a 220 V three phase, 50HZ supply. Calculate the line currents and the power drawn by the circuit.
Answer
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Derive the relationship between line and phase voltage in a 3-phase balanced delta connected system.
Answer
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A balanced three phase load is connected to balanced 3 phase power system. The line voltage is 440 volts and the line current is 8 A. the angle of the phase impedance of the load 50. Find the complex power and real power absorbed by the load.
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Derive the transient response for series RL circuit for ac excitation using differential equation approach.
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A series RC circuit with R = 10 ohms and C = 1 F has a sinusoidal voltage source V = 200 volts applied at a time t=0. Find the expression for the total current. Use differential equation method.
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Derive the transient response for parallel RC circuit for DC excitation using Laplace approach.
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A series R C circuit with R = 80 OHMS and C = 30 F has a sinusoidal excitation V(t) = 200 Sin 400t. Find the total current assuming that the capacitor is initially uncharged. Use time domain approach.
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Find the transfer impedance of the following circuit shown in Figure.1
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The Laplace transform of a voltage v(t) is V(s)=(s+6)/(s+2)(s+4). Draw poles and zeros of this function and determine v(t) using pole-zero plot.
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For the given network function draw pole zero diagram and hence obtain the time domain response i(t) if I(s) = 10s / (s+1)(s^2+4s+8).
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Find the driving point admittance function Y(s) for the network shown in Figure.2 and also plot the pole zero diagram.
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If a 2Ω resistor is connected across port-2 of a two-port network then what must be the voltage applied at port-1 to produce 0.5A in the 2Ω resistor. The Z parameters of a two port network are Z11 = 2.1 Ω, Z22 = 1.6 Ω, Z12 =Z21=0.6Ω.
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Two identical sections of the network shown in Figure.3 are connected in cascaded. Obtain Y-parameters of the overall connection.
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In the two-port network shown in Figure.4, compute h-parameters from the following data: i) With the output port short-circuited:V1 = 25 V, I1 = 1 A, I2 =2 A ii) With the input port open-circuited:V1 = 10 V,V2 = 50 V, I2 =2 A
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Determine ABCD Parameters from Y-parameters of the network shown in Figure.5.
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Obtain design equations of high pass filter?
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State and explain different properties of a Fourier Transformers.
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Explain the design procedure for band pass filter and draw its characteristic.
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Let the CTFT X(ω) of the signal x(t) is as given in Figure.6. Plot the spectrum of the following signals using the CTFT properties. How is the spectrum X(ω) modified in each case (i) e^(-j5t) x(t) (ii) x(t)x(t) and (iii) t^2 x(t)
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