JNTU
JNTU B.Tech II BASIC ELECTRICAL AND ELECTRONICS ENGINEERING Previous Question Paper (September - 2021 - R18)
Answer any five questions. All questions carry equal marks.
Main
Explain the ideal voltage source and current source.
Answer
An ideal voltage source is a two-terminal circuit element that maintains a constant terminal voltage regardless of the current flowing through it. Its internal resistance is zero, meaning the terminal voltage remains fixed at its rated value even if the load current changes. The V-I characteristic is a horizontal line parallel to the current axis.
An ideal current source is a two-terminal circuit element that provides a constant current to any load connected across its terminals, regardless of the voltage across it. Its internal resistance is infinite, ensuring the current remains constant regardless of the terminal voltage. The V-I characteristic is a vertical line parallel to the voltage axis.
A 10µF, a 20µF and a 40µF capacitor are connected in series to a 230 volts source of e.m.f.
i) What is the equivalent capacitance?
ii) What is the magnitude of charge across each capacitor?
iii) What is the potential difference across each capacitor?
Answer
Given: C1 = 10 µF, C2 = 20 µF, C3 = 40 µF, V = 230 V.
i) The equivalent capacitance (Ceq) for capacitors in series is given by:
ii) The total charge (Q) supplied by the source is:
Since the capacitors are in series, the charge across each capacitor is the same:
iii) The potential difference across each capacitor (V = Q/C) is:
Derive the relationship between line current, line voltage, phase current and phase voltage in case of star and delta connection of three phase windings.
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Explain how the electrical energy from a supply company is distributed in a building.
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Describe the function of switch fuse unit with diagram.
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What is meant by battery backup? Give its four important applications.
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Explain the procedure of calculating energy consumption in the building with suitable example.
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Explain the principle of working of transformer. What is meant by step up and step down transformers?
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The primary winding of a 50 Hz transformer has 480 turns and is fed from a 6400 V supply. Determine (i) the peak value of flux in the core and (ii) the secondary voltage if the secondary winding has 20 turns.
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Explain the construction features of a DC motor.
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A 6 pole induction motor is fed from a 50 Hz supply. IF the frequency of the rotor emf at full load is 2 Hz, find the full load slip and speed.
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Explain how a p-n junction can be used to work as a diode.
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What is a Zener diode? How is it different from a p-n junction diode?
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Explain the working principle of an p-n-p transistor.
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Explain the characteristics of CB and CC configurations of Transistors.
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