JNTU
JNTU B.Tech II ELECTRICAL CIRCUITS Previous Question Paper (March 2022 - R13)
Answer any five questions. Each carries equal marks.
Main
Find the current flowing through 20Ω resistor shown in the figure 1.
Answer
To find the current through the 20Ω resistor, first identify the circuit configuration. Assuming a standard network where the 20Ω resistor is in series with a voltage source or part of a bridge circuit, apply Kirchhoff's Voltage Law (KVL) or Node Voltage Analysis. If the 20Ω resistor is in a branch with a voltage V and a total series resistance R_eq, the current I is calculated as:
If the circuit involves multiple loops, set up the mesh equations: ΣV = Σ(I * R). Solve the resulting system of linear equations for the mesh current passing through the 20Ω branch. If the resistor is shared between two meshes with currents I1 and I2, the current through the resistor is the algebraic difference (I1 - I2) or (I2 - I1) depending on the assumed direction.
Derive the expressions required for the conversion of star to delta transformation.
Answer
For a star network with resistances R1, R2, and R3 connected to nodes 1, 2, and 3, and a delta network with resistances R12, R23, and R31 connected between the same nodes, the transformation is derived by equating the resistances between any two terminals. The resistance between nodes 1 and 2 in delta is R12 in parallel with (R23 + R31), and in star, it is (R1 + R2). Equating these for all pairs yields:
- R12 = (R1*R2 + R2*R3 + R3*R1) / R3
- R23 = (R1*R2 + R2*R3 + R3*R1) / R1
- R31 = (R1*R2 + R2*R3 + R3*R1) / R2
These expressions allow the conversion from a star configuration to an equivalent delta configuration by calculating the sum of the products of the star resistances taken two at a time, divided by the resistance of the star arm not connected to the junction between the two delta nodes.
A current waveform as shown in the figure 2 is applied to a capacitor of 2µF. Obtain the voltage waveform equation.
Answer
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What is the difference between an ideal source and a practical source? Draw the relevant characteristics of the above sources.
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The voltage of a circuit is
The average power, reactive volt-amperes and apparent power.
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Find the circuit elements if
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Define the following: i) RMS value ii) Average Value and iii) Form factor of an alternating quantity.
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The equation of an alternating quantity is
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Draw and explain the locus diagram of series RL circuit with the variation of resistance value.
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A resistance and a capacitance is connected in series across a 150V AC 40 Hz supply. The current in the circuit is measured as 5A. If the frequency of the supply is raised to 50 Hz, the current becomes 6A. Find the values of resistance and capacitance.
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State and explain Faraday’s law of Electro-magnetic Induction.
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Obtain the expression for resonant frequency of RLC series circuit excited by constant voltage and variable frequency.
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Write a short note on Duality and Dual networks.
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Define the following terms: i) Node ii) Tree iii) Sub-graph iv) Link v) Twig.
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Find the current in the 50 Ω resistor in the figure 3 using superposition theorem.
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Prove that the efficiency of a network supplying maximum power is 50%.
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