Jawaharlal Nehru Technological University Hyderabad
Jawaharlal Nehru Technological University Hyderabad B.Tech II ELECTRICAL SYSTEMS Previous Question Paper (October - 2020 - R13)
Answer any five questions. All questions carry equal marks.
Main
Define the Ohm's law and mention units of each quantity?
Answer
Ohm's law states that the current flowing through a metallic conductor is directly proportional to the potential difference applied across its ends, provided that the physical conditions such as temperature remain constant.
Where:
- V is the potential difference measured in Volts (V).
- I is the current measured in Amperes (A).
- R is the resistance measured in Ohms (Ω).
State and explain the Kirchoff’s Laws.
Answer
Kirchhoff’s laws are fundamental principles used to analyze electrical circuits:
1. Kirchhoff’s Current Law (KCL): Also known as the junction rule, it states that the algebraic sum of currents meeting at any junction in an electrical circuit is zero. This is based on the law of conservation of charge.
This implies that the total current entering a junction must equal the total current leaving it.
2. Kirchhoff’s Voltage Law (KVL): Also known as the loop rule, it states that the algebraic sum of all potential differences (voltages) around any closed loop in a circuit is zero. This is based on the law of conservation of energy.
In any closed loop, the sum of the electromotive forces (EMFs) is equal to the sum of the potential drops across the resistances in that loop.
State and explain superposition theorem.
Answer
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In the circuit as shown in following figure, maximum power is absorbed by the resistance R. Compute the value of R and the value of maximum power consumed.
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A coil of resistance 10 ohms, inductive reactance of 20 ohms is connected in series with a capacitive reactance of 40 ohms across a 230 V, 50 Hz supply. Determine the following:
- Inductance and capacitance of the circuit
- Total impedance of the circuit
- Current
- Power factor and power consumed
- Draw the phasor diagram.
Answer
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What are the advantages of three phase system over single phase system?
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Obtain the response of R-L circuit for DC energy excitation using Laplace transform method.
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What is a transformer? How does it transfer electrical energy from one circuit to another?
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A 3300/300 V single phase transformer gives 0.9A and 50W as ammeter and wattmeter readings when supply is given to the low voltage winding and high voltage winding is kept open, determine the i) power factor of no load current, ii) Magnetizing Component, and iii) Iron loss component.
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A 200/1000V, 50Hz single phase transformer gave the following test results: O.C. Test (LV Side) : 200V, 0.7A, 70W; S.C. Test (HV Side): 15V, 10A, 85W. Calculate the parameters of the equivalent circuit referred to the LV Side.
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Derive the expression for emf generated in a DC generator.
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Describe the double field revolving theory with neat diagram.
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Explain the working principle of single phase induction motor.
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