JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II Year NETWORK THEORY Previous Question Paper (September/October - 2023 - R15)
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
What are the reasons for unbalance of phases in a 3-phase system?
Answer
Unbalance in a 3-phase system occurs primarily due to unequal load impedances connected across the phases or an asymmetrical distribution of single-phase loads across the three phases. It can also be caused by faults, such as line-to-ground or line-to-line short circuits, or by asymmetrical line impedances.
What are the advantages of poly phase system?
Answer
Polyphase systems offer several advantages over single-phase systems: they provide constant instantaneous power, leading to smoother operation of motors; they are more efficient in terms of material usage for a given power transmission; and polyphase motors are self-starting and have superior torque characteristics.
Why the current in a pure inductance cannot change in zero time?
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Define Natural and Forced response in transient circuits.
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What is a transfer function?
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Describe time domain behavior from pole zero plot.
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Find the z parameters of the two-port network.
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Define reciprocity condition of two port network parameters in terms of h-parameters.
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Define Characteristic Impedance of filters.
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List out two applications of filter circuits?
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Part B
Derive the relationship between line and phase quantities in a 3-phase Star balanced connected system.
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Three impedances of each (5+j12) ohms is connected in star are connected to a 220 V three phase, 50 HZ supply. Calculate the line currents and the power drawn by the circuit.
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Explain how reactive power can be measured in three phase circuits.
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Discuss the effect of power factor on wattmeter readings in two wattmeter method.
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A series RL circuit with R= 5 ohms and L= 1H is excited by a dc voltage of 50 V. Assume the initial current flowing through the inductor to be 5 A and find the current i(t) for t>0 by using Laplace transform method.
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A series RLC circuit with R= 3 ohms, L= 1H and C= 0.5F is excited by 10 V dc source. Obtain an expression for current in the circuit if the circuit is relaxed initially by LT method.
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A Series R-C Circuit is excited with DC Voltage V at t = 0. Derive the complete expression for current i(t) using Laplace transform method.
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The 12 V battery shown in figure is disconnected at t = 0. Find the inductor current iL(t) and its voltage VL(t) for t>0.
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Explain the necessary conditions for driving point functions.
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The transform voltage V(s) of a network is given by
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What is the necessity of transform impedance and transform circuits?
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What is the physical interpretation of complex frequency?
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The Z-parameters of a two-port network are Z11= 20 ohms, Z22= 30 ohms and Z12=Z21= 10 ohms. Find Y, h and ABCD parameters.
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Write the basic equations for Y parameters. State the symmetry and reciprocity condition in terms of ‘Y’ parameters.
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Find the h parameters for the circuit shown in fig. The values of y1 = 10 S, y2 = 8 S and y3 = 2 S.
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An LPF is composed of a symmetrical ℿ - network. Each series branch is a 0.02 H inductor and shunt branch is a 2µF capacitor. Find a) cut-off frequency, b) nominal impedance, c) characteristic impedance at 200 Hz and 2000 Hz, and d) Attenuation at 200 Hz and 2000 Hz.
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Explain various filters.
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What are the properties of Fourier transforms?
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