JNTU
JNTU B.Tech II Year BASIC ELECTRICAL AND ELECTRONICS ENGINEERING Previous Question Paper (March - 2021 - R18)
Answer any five questions. All questions carry equal marks.
Main
State and explain Kirchoff’s Laws.
Answer
Kirchhoff’s Current Law (KCL) states that the algebraic sum of currents meeting at any junction or node in an electrical circuit is zero. Mathematically, ΣI = 0. This is based on the principle of conservation of charge, implying that the total current entering a junction must equal the total current leaving it.
Kirchhoff’s Voltage Law (KVL) states that the algebraic sum of all voltages around any closed loop in a circuit is zero. Mathematically, ΣV = 0, or the sum of EMFs equals the sum of voltage drops in a loop. This is based on the principle of conservation of energy, as the potential energy gained by charges moving through a source must be dissipated across the circuit components.
Six resistors are connected as shown in figure. If a battery having an emf of 30V and an internal resistance of 2 ohms is connected to terminals A and B. Find: i) Current supplied from battery ii) Potential difference across 12 ohms resistance.
Answer
To find the current supplied by the battery, first determine the equivalent resistance of the network connected to terminals A and B. Assuming the six resistors are arranged in a standard bridge or series-parallel configuration, calculate the total external resistance R_ext. The total circuit resistance is R_total = R_ext + R_internal, where R_internal = 2 Ω.
i) The current supplied by the battery is calculated using Ohm's Law: I = E / R_total, where E = 30 V.
ii) To find the potential difference across the 12 Ω resistor, identify its position in the circuit. If it is in series with the main current, V = I × 12. If it is part of a parallel branch, use the current division rule to find the current flowing through that specific branch (I_branch) and then calculate V = I_branch × 12.
What are the merits of polyphase system over a single phase system?
Answer
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A choke coil of resistance 8 ohms and inductance of 0.5H is connected in series with a capacitor of capacitive 125 × 10-6 Farads across a 230V, 50Hz supply, calculate: i) The inductive reactance ii) Current iii) Voltage across the coil and across the capacitor iv) p.f of the circuit.
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Explain the construction and working principle of MCCB.
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What is meant by battery backup? Give its four important applications.
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Explain different types of wires used in electrical Installations.
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Why do you need to improve the p.f of a system?
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Explain the construction and working principle of DC generators.
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A 100 kVA, 2200/400 V transformer has R1= 0.3 ohm, X1 = 1.1 ohm, R2= 0.01 ohm and X2 = 0.035 ohm. Calculate (i) the equivalent impedance of the transformer referred to the primary and (ii) total copper losses.
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List out the speed control of three-phase induction motor. Explain any one method.
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A 250V, DC shunt motor takes a line current of 20A resistance of shunt field winding is 200 ohms and resistance of the armature is 0.3 ohms. Find the armature current and the back emf.
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Describe the working of a PN junction diode with neat diagram.
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Explain the V-I characteristics of Zener diode.
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Compare between the CE, CB and CC configurations of transistor.
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Explain the construction and principle of operation of FET with neat diagram.
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