JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II BASIC ELECTRICAL ENGINEERING Previous Question Paper (November/December - 2017 - R15)
Note: This question paper contains two parts A and B. Part A is compulsory which carries 25 marks. Answer all questions in Part A. Part B consists of 5 Units. Answer any one full question from each unit.
PART- A
State the Superposition theorem.
Answer
The Superposition theorem states that in any linear, bilateral network containing two or more independent sources, the response (voltage or current) in any branch is equal to the algebraic sum of the individual responses caused by each independent source acting alone, while all other independent sources are replaced by their internal resistances.
For this purpose, independent voltage sources are replaced by a short circuit (zero internal resistance) and independent current sources are replaced by an open circuit (infinite internal resistance).
A conductor is 50 m long. It has a cross – sectional area of 2 mm² while it offers a resistance of 10 Ω. Find the conductivity of the material.
Answer
To find the conductivity, we first calculate the resistivity of the material using the resistance formula:
Given: R = 10 Ω, L = 50 m, and A = 2 mm² = 2 × 10⁻⁶ m². Rearranging for resistivity (ρ):
Conductivity (σ) is the reciprocal of resistivity:
How does inductance and capacitance will behave when an alternating sinusoidal voltage is applied to them.
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A coil has an inductance of 50 mH and negligible resistance. Find its reactance at 100 Hz.
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What are the conditions to be fulfilled to work as step up transformer?
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Distinguish between Ideal and a practical transformer.
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Explain the principle of operation of DC Generator.
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What is the difference between a separately excited and a self excited generator?
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List the advantages of Moving coil instruments.
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List the necessary purpose of providing the controlling torque in indicating Instrument.
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PART-B
State and explain Kirchhoff’s current law and Kirchhoff’s Voltage law.
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Find the equivalent capacitance of the system across terminals a-b shown in the figure 1.
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Explain the process followed for Star (Y) – Delta (Δ) transformation.
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Find the Thevenin’s equivalent for the network shown in figure 2 across RL.
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How do you generate alternating emf and explain the terms phase angle and Amplitude.
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Find the average and rms of the waveform shown in the figure 3.
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Explain the terms with respect to Alternating Quantity: i) Average value ii) Form factor.
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A voltage of 400 V is applied to a series circuit containing a resistor, an inductor and a capacitor. The respective voltages across the components are 250 V, 200 V and 180 V and the current is 5 A. Determine the phase angle of the current.
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Explain the principle of operation of a transformer.
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Define the term Regulation and derive the expression for regulation of a transformer.
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Explain in detail about Core type and shell type transformers.
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A 200 KVA single – phase transformer has 1000 turns in the primary and 600 turns on the secondary. The primary winding is supplied from a 440 V, 50 Hz source. Find the i) Secondary voltage at no load and ii) Primary and secondary currents at the full load.
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Distinguish between the short shunt and long shunt compound generators.
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A 4 pole lap wound DC Generator has 680 conductors; a flux of 30 mWb per pole driven at 550 rpm. Find the generated emf.
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Explain in detail about lap and wave windings in DC Machines.
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A three phase, 50 Hz, 6- pole induction motor runs at 950 rpm. Calculate: i) the synchronous speed ii) the slip and iii) frequency of the rotor emf.
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Explain the different methods of generating Damping torque and explain them with neat sketches.
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List the different types of errors that occur in Moving iron instruments and how can we compensate them.
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Explain in detail about Indicating, Integrating and recording electrical instruments with an example of each type.
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With a neat sketch explain the working of Repulsion type moving iron instrument.
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