JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II ELECTRICAL CIRCUIT ANALYSIS Previous Question Paper (March - 2021 - R18)
Answer any five questions. All questions carry equal marks.
Main
Find the Thevenin’s equivalent circuit of the circuit shown in figure 1 across the terminals ab. And also find the current through RL = 16 ohm.
Answer
To find the Thevenin equivalent circuit across terminals ab, we first determine the open-circuit voltage Vth. By applying nodal analysis or mesh analysis to the circuit, Vth is calculated as the voltage across the open terminals. Next, we determine the Thevenin resistance Rth by deactivating all independent sources (short-circuiting voltage sources and open-circuiting current sources) and calculating the equivalent resistance seen from terminals ab. Once Vth and Rth are obtained, the Thevenin equivalent circuit consists of a voltage source Vth in series with a resistor Rth. The current through the load resistor RL = 16 Ω is then found using the formula:
Substituting RL = 16 Ω into this expression yields the final current value.
Compute the current in 23 ohm resistor using superposition theorem for the circuit shown in figure 2.
Answer
To compute the current in the 23 Ω resistor using the superposition theorem, we consider the contribution of each independent source acting alone while replacing all other independent voltage sources with short circuits and all independent current sources with open circuits.
- Deactivate all sources except the first one and calculate the current component I' flowing through the 23 Ω resistor using series-parallel circuit reduction or nodal analysis.
- Repeat this process for every independent source in the circuit to find subsequent current components I'', I''', and so on.
- The total current through the 23 Ω resistor is the algebraic sum of all individual components: I = I' + I'' + ...
Ensure that the direction of each component current is carefully tracked to maintain consistent polarity during the final summation.
Find the value of RL so that maximum power is delivered to the load resistance shown in figure 3.
Answer
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Define duality and explain in detail about the dual networks.
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Derive an expression for current response of RLC series circuit transient for unit step input.
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For a source free RLC series circuit, the initial voltage across C is 10V and the initial current through L is zero. If L = 20mH, C = 0.5 μF and R = 100 Ω. Evaluate i(t).
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Obtain the current expression in a RL series circuit when it is excited by υ(t) = Vm sin ωt. Also, draw the waveform for power.
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Define RMS value and Average value of an alternating quantity. Determine these values for a half wave rectified sine wave.
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A three phase delta connected load has Zab = (100+j0) Ω, Zbc = (-j100) Ω and Zca = (j70.7) Ω is connected to a balanced 3 phase 400V supply. Determine the line currents Ia, Ib and Ic. Assume the phase sequence abc.
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Explain the following:
Dot convention in coupled circuits.
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Ideal transformer.
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Complex power in a 1-φ circuit.
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A series RLC circuit with R = 3 Ω, L = 1H and C = 0.5F, is excited by a unit step voltage. Obtain the expression for I(t) using Laplace Transform method. Assume that the circuit is initially relaxed. Sketch the variation of I(t) and state whether the circuit is over damped, or under damped or critically damped.
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Obtain the expression for Y-parameters in terms of transmission parameters.
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Determine the Hybrid parameters for the Two Port network shown in figure 4.
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