JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II Year FUNDAMENTALS OF ELECTRICAL ENGINEERING Previous Question Paper (May/June - 2019 - 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
Briefly explain the relationship between current and voltage for passive elements.
Answer
For passive elements, the relationship between voltage (v) and current (i) is defined by their specific physical properties:
- Resistor: Follows Ohm's Law, where voltage is directly proportional to current: v = iR
- Inductor: Voltage is proportional to the rate of change of current: v = L(di/dt)
- Capacitor: Current is proportional to the rate of change of voltage: i = C(dv/dt)
Explain Faraday’s Laws of electromagnetic induction.
Answer
Faraday's laws of electromagnetic induction describe the process by which a changing magnetic field induces an electromotive force (EMF) in a conductor. The laws are stated as follows:
- First Law: Whenever the magnetic flux linked with a circuit changes, an EMF is induced in it. This induced EMF lasts only as long as the change in flux continues.
- Second Law: The magnitude of the induced EMF is directly proportional to the rate of change of magnetic flux linkages.
Mathematically, the second law is expressed as:
where e is the induced EMF, N is the number of turns in the coil, and dΦ / dt is the rate of change of magnetic flux. The negative sign, derived from Lenz's Law, indicates that the induced EMF opposes the change in flux that produced it.
What is Power factor? Explain.
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Define the terms band width and Q factor.
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State Norton’s Theorem.
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State and explain Reciprocity theorem.
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Explain O.C.C characteristics of DC generator.
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With the help of neat circuit diagram, explain different types of DC motors.
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Give the principle of operation of 1-ϕ synchronous generator.
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Explain the principle of operation of 1-ϕ induction motors.
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Part B
For the circuit shown in figure 1, find the total resistance between terminals A and B, the total current drawn from a 6V source connected from A and B, and the current flowing through 4.7 kΩ.
Answer
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What is self and Mutual inductances? Explain with necessary equations.
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What is coefficient of coupling? Derive its equation.
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A two branch parallel circuit with one branch of R = 100Ω and a single unknown element in the other branch, has the following applied voltage and total current. V = 2000 cos (1000 t - 45°) volts; It = 45 sin (1000 t + 135°) Amperes. Find the unknown element.
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Obtain the current expression when R-L circuit is excited by an A.C source. Draw the vector diagram.
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For the circuit shown in figure 2, what will be the value of RL to get the maximum power across it?
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Find the current ‘I’ in the circuit shown in figure 3 by using the superposition theorem.
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Explain the working principle and constructional details of DC Motor.
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Derive the expression for emf generated in DC generator.
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Explain the principle of operation and constructional details of single-phase Transformers.
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Give the equivalent circuit of 1-ϕ transformer. Explain the significance of each term in the equivalent circuit. Mention few advantages of equivalent circuit.
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