JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD

JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech I Year BASIC ELECTRICAL ENGINEERING Previous Question Paper (September - 2023 - R22)

B.Tech | I Year | I-I | R22 | September - 2023

Answer PaperPaper Code: 181ABMaximum Marks: 60Time: 3 Hours

Note: Part-A is a compulsory question. Part-B consists of five questions by choosing one from each unit.

Part A

Answer all sub-questions:

10 marks

What are the limitations of Ohm’s law?

1 marks

Answer

The limitations of Ohm's Law include:

It is not applicable to non-linear devices such as diodes, transistors, and vacuum tubes, where the current does not vary linearly with voltage.
It does not apply to unilateral networks, which allow current to flow in only one direction (e.g., semiconductor devices).
It does not hold for materials where resistance changes with temperature or current, such as thyrite or incandescent lamp filaments.

State Norton’s theorem.

1 marks

Answer

Norton's Theorem states that any linear, active, two-terminal bilateral network containing energy sources and resistances can be replaced by an equivalent circuit consisting of a constant current source (I_N) in parallel with a Norton resistance (R_N). The current source is equal to the short-circuit current across the terminals, and the resistance is the equivalent resistance of the network viewed from the same terminals with all independent sources turned off.

Write any two advantages and disadvantages of 3-phase system.

1 marks

Answer

Define power factor of an AC circuit.

1 marks

Answer

Write the applications of auto-transformer.

1 marks

Answer

Define the regulation of a transformers.

1 marks

Answer

Why the core of the machine is laminated?

1 marks

Answer

Why single-phase induction motor is not self-starting?

1 marks

Answer

What is the function of MCCB?

1 marks

Answer

What are the characteristics of batteries for longer life?

1 marks

Answer

Part B

210 marks

What is difference between a current source and a voltage source? Explain about ideal and practical voltage and current sources.

5 marks

Answer

A series R-C circuit consists of a resistor of 10 Ω and capacitor of 0.1 F with a constant voltage of 20 V, is applied to the circuit at t=0. Obtain the current equation. Determine voltage across resistor and capacitor.

5 marks

Answer

310 marks

Obtain the Transient Response of series R-L circuit with DC excitation.

5 marks

Answer

Three resistances 2 ohms, 4 ohms and 6 ohms are connected in series across 24V supply. Find the voltages across three resistors and current through each resistor. Also calculate the total power consumed in the circuit.

5 marks

Answer

410 marks

Derive expression of resonance frequency for series RLC circuit.

6 marks

Answer

Derive the relation between line current and phase current in case of three phase delta connected balanced load.

4 marks

Answer

510 marks

A voltage of 125 V, 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.

5 marks

Answer

With the help of phasor diagram, show that the current drawn by the R-L series circuit lags the applied voltage by an angle θ with respect to voltage.

5 marks

Answer

610 marks

Draw and explain the equivalent circuit of a single-phase transformer.

5 marks

Answer

The efficiency of a 10 kVA, 2000/400 V single phase transformer at unity power factor is 97% at rated load and at half rated load. Determine the transformer core losses and copper losses.

5 marks

Answer

710 marks

Explain briefly the principle of working of a transformer and show the voltage ratio of the primary and secondary windings is same as their turn’s ratio.

5 marks

Answer

Find the efficiency of a 150 kVA transformer at 25% of its full load at 0.8 power factor lagging if copper losses are 1600 W at full load and iron losses are 1400 W.

5 marks

Answer

810 marks

With the help of a neat sketch, explain the construction and working principle of a DC machine.

5 marks

Answer

The frequency of the e.m.f. in the stator of a 4-pole induction motor is 50 Hz, and that in the rotor is 2 Hz. What is the slip and at what speed is the motor running?

5 marks

Answer

910 marks

Explain the concept behind the generation of rotating field in a three-phase induction motor.

5 marks

Answer

Explain the construction and working of a three-phase induction motor.

5 marks

Answer

1010 marks

Explain the working principle of SFU and MCB.

5 marks

Answer

What are the drawbacks of low power factor? Describe how it is improved?

5 marks

Answer

1110 marks

Explain the components of LT switch gear in detail.

5 marks

Answer

Briefly explain following: (i) Need of Earthing (ii) Battery backup.

5 marks

JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech I Year BASIC ELECTRICAL ENGINEERING Previous Question Paper (September - 2023 - R22)

Part A

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Part B

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