JNTU
JNTU B.Tech II BASIC ELECTRICAL ENGINEERING Previous Question Paper (August/September - 2022 - R13)
Answer any five questions. All questions carry equal marks.
Main
State and explain superposition theorem.
Answer
The Superposition Theorem states that in a linear, bilateral network containing two or more independent sources, the response (voltage or current) in any branch is the algebraic sum of the individual responses produced by each source acting alone, while all other independent sources are replaced by their internal resistances.
To apply the theorem, follow these steps:
- Retain one independent source and replace all other independent voltage sources with a short circuit (0 Ω) and all other independent current sources with an open circuit (∞ Ω).
- Calculate the current or voltage in the desired branch due to the single active source.
- Repeat the process for each independent source present in the circuit.
- Determine the total response by taking the algebraic sum of all the individual responses calculated in the previous steps.
Calculate the resistance between the points A and B for the following network (figure 1):
Answer
Since the figure is not provided in the prompt, the general procedure to determine the equivalent resistance between terminals A and B involves identifying series and parallel combinations of resistors.
- Identify resistors connected in series: If the same current flows through multiple resistors, they are in series, and their equivalent resistance is the sum of their individual values (R = R1 + R2 + ...).
- Identify resistors connected in parallel: If the same voltage appears across multiple resistors, they are in parallel, and their equivalent resistance is calculated using the reciprocal formula: 1/R = 1/R1 + 1/R2 + ...
- Simplify the network step-by-step by replacing these combinations with their equivalent resistances until the entire network reduces to a single equivalent resistance between terminals A and B.
- If the circuit contains delta (Δ) or star (Y) configurations that cannot be simplified by series/parallel rules, apply the Delta-to-Star or Star-to-Delta transformation formulas to convert the network into a simpler form.
Using delta to star transformation, determine the resistance between terminals a and b and the total power drawn from the supply in the circuit for the following figure 2:
Answer
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State and explain Thevenin’s theorem.
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Explain the following terms with respect to alternating quantities: i) Instantaneous value, ii) Cycle, iii) Time period, iv) Frequency, v) Amplitude.
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Find the average value of the periodic function shown below in figure 3:
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Draw the phasor and wave diagram for voltage and current in an R – C series circuit connected with sinusoidal excitation.
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A voltage of 125 V at 50 Hz is applied across a non-inductive resistor connected in series with a capacitor. The current in the circuit is 2.2 A. The power loss in the resistor is 96.8 W and that in the capacitor is negligible. Calculate the resistance and the capacitance.
Answer
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Distinguish between core-type and shell-type transformers in detail.
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The secondary of a 500 kVA, 4400/500 V, 50 Hz, single-phase transformer has 500 turns. Determine (i) emf per turn, (ii) primary turns, (iii) secondary full-load current, and (iv) maximum flux.
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Explain the principle of working of a transformer. Draw its phasor diagram on no-load.
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A 230/110 V single-phase transformer has a core loss of 100 W. If the input under no-load condition is 400 VA, find core loss current, magnetizing current, and no-load power factor angle.
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Explain the principle of operation and brief constructional details of a DC machine.
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A three-phase, four-pole induction motor is supplied from three-phase, 50 Hz AC supply. Calculate (i) synchronous speed, (ii) rotor speed when slip is 4%, and (iii) rotor frequency, when rotor runs at 600 rpm.
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Explain the various methods for providing damping torque in an instrument.
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Explain construction and principle of operation of a moving coil instrument with a neat diagram.
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