JNTU
JNTU B.Tech II NETWORK ANALYSIS Previous Question Paper (November/December - 2018 - R16)
Note: Part A is compulsory (25 marks). Part B consists of 5 Units. Answer any one full question from each unit (10 marks each).
Main
Answer all questions in Part A.
What is an Ideal transformer?
Answer
An Ideal Transformer is a theoretical model of a transformer that assumes perfect characteristics. It is defined by the following properties:
- Zero winding resistance (no copper losses).
- Infinite permeability of the core (no magnetizing current required).
- Zero leakage flux (perfect coupling, coefficient of coupling k = 1).
- Zero hysteresis and eddy current losses (no core losses).
Where a is the turns ratio.
Discuss the dot convention between magnetically coupled coils.
Answer
The dot convention is a graphical method used to determine the polarity of the induced voltage in magnetically coupled coils without needing to know the physical winding direction. The rules are:
- If current enters the dotted terminal of one coil, the dotted terminal of the other coil becomes positive with respect to its undotted terminal.
- If current leaves the dotted terminal of one coil, the dotted terminal of the other coil becomes negative with respect to its undotted terminal.
This convention simplifies the formulation of KVL equations for coupled circuits by clearly indicating whether mutual inductance M adds to or subtracts from self-inductance.
What is resonance? Explain.
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What is the significance of power factor?
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Explain the significance of average value.
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What are the Laplace transform of step and exponential functions?
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Define poles and zeros in a transfer function.
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What is a driving point in transfer function? Explain.
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Write the Properties of LC Networks.
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State Foster’s Reactance theorem.
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Explain the following:
i) Self inductance (L)
ii) Mutual inductance (M)
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An Iron ring of mean length 50 cm has an air gap of 1 mm and a winding of 200 turns. If the relative permeability of the Iron is 400, when a current of 1 Amp flows in the winding, determine the flux density. Neglect leakage and fringing.
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Define and explain the following with an example:
Oriented Graph
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Tree of a Graph
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Tie set and a basic Tie set
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Cut set and a basic Cut set
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R-C series circuit is suddenly excited from a step voltage V. Derive an expression for the current as a function of time and draw the graph current Vs Time.
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An inductive coil of Resistance R and inductance L is connected in parallel with a capacitor C. Derive the expressions for resonant frequency and Q factor.
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A series RLC circuit is connected across a variable frequency supply and has R = 12 ohms, L = 1mH and C = 1000pF. Calculate:
Resonant frequency
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Q factor
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Half power frequencies. Derive the formulae used.
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Derive expression for R.M.S and average value of a sinusoidal alternating quantity.
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A pure inductance of 5 mH carries a current of the wave form shown in figure 1. Sketch the waveform of V(t) and P(t). Determine the average value of power.
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A capacitor of 100 μF is connected across 200 V, 50 Hz, Single phase supply. Calculate: i) The reactance of the capacitor ii) RMS value of the current iii) The maximum value of the current.
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When an impulse voltage is impressed across R-C circuit, derive an expression for its current response.
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Determine the ‘h’ parameters of the network shown in figure 2.
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Define Z and Y parameters of a two port network and determine the relationship between the above parameters.
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Explain clearly the following terms:
Propagation constant and characteristic impedance
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Attenuation constant.
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What is a high pass filter? In what respects it is different from a low pass filter?
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Derive the equations to find the inductances and capacitances of a constant K high pass filter.
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Explain the variation of Attenuation, phase shift and characteristic impedance of Band pass filter.
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Draw the circuit diagram for T and π sections of composite filter.
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