JNTU
JNTU B.Tech II ELECTRICAL CIRCUITS Previous Question Paper (September - 2021 - R15)
Answer any five questions. All questions carry equal marks.
Main
Distinguish between passive and active elements with suitable examples.
Answer
An active element is a circuit component capable of generating or delivering energy to the network. These elements can control the flow of charge and are characterized by their ability to provide power gain. Examples include voltage sources, current sources, transistors, and operational amplifiers.
A passive element is a circuit component that cannot generate energy but can only store or dissipate it. These elements are incapable of power gain and do not control the flow of charge. Examples include resistors (which dissipate energy as heat), inductors (which store energy in a magnetic field), and capacitors (which store energy in an electric field).
Find the voltage and current source equivalent representation of the following network across AB, as shown in figure 1.
Answer
To find the equivalent representation of a network across terminals AB, we determine the Thevenin equivalent (voltage source) and Norton equivalent (current source) circuits.
- Thevenin Voltage (Vth): Calculate the open-circuit voltage across terminals AB. This is the voltage at the output terminals when no load is connected.
- Thevenin Resistance (Rth): Deactivate all independent sources (replace voltage sources with short circuits and current sources with open circuits) and calculate the equivalent resistance looking into terminals AB.
- Vth = Isc × Rth
- Norton Current (Isc): Calculate the short-circuit current by placing a short across terminals AB. The equivalent current source is Isc in parallel with Rth.
The voltage source representation consists of a voltage source Vth in series with resistance Rth, while the current source representation consists of a current source Isc in parallel with resistance Rth.
Find the equivalent resistance across A, B terminals of the network shown in figure 2.
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Using mesh analysis, determine the voltage V which gives a voltage of 50V across 10Ω resistor shown in figure 3.
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Determine the average and effective values of saw-tooth waveform as shown in figure 4.
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For the circuit shown in figure 5, determine the total impedance, total current and phase angle.
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Derive an expression for the current, impedance, average power for a series RC circuit excited by a sinusoidally alternating voltage and also find the power factor of the circuit. Draw the phasor diagram.
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A series R-L series circuit having a resistance of 4 Ω and 3 Ω inductive reactance is fed by 100 V, 50 Hz, 1-phase supply. Find current, power drawn by the circuit and power factor.
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Draw the locus diagram of Parallel RC circuit and explain.
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Derive the expressions for half power frequencies for a RLC series circuit.
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Derive coefficient of coupling for two mutually coupled coils.
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An iron ring 10cm diameter and 15cm2 cross section is wound with 250 turns of wire for a flux density of 1.5wb/m2 and permeability 500. Find the exciting current, the inductance and the stored energy.
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Write short notes on Incidence matrix of a given network shown in figure 6.
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Draw the dual of the following network shown in figure 7.
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State and explain Thevenin’s theorem.
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Using Norton’s theorem, find the current in the 2Ω resistor as shown figure 8 in the circuit.
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