JNTU
JNTU B.Tech II FUNDAMENTALS OF ELECTRICAL ENGINEERING Previous Question Paper (November/December - 2018 - 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. Each question carries 10 marks and may have a, b, c as sub questions.
Part A
Write a note on independent and dependent sources.
Answer
An independent source provides a specified voltage or current that is independent of any other circuit element or variable. A dependent (controlled) source provides a voltage or current whose value depends on a voltage or current elsewhere in the circuit.
Three 17.2 ohm resistors are connected in Star. Calculate the star equivalent resistances.
Answer
For a star connection where all three resistors are equal (Ra = Rb = Rc = 17.2 Ω), the star equivalent resistances are simply the values of the resistors themselves in the star configuration. Thus, each branch resistance is 17.2 Ω.
Define Form Factor and Peak Factor.
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Write the characteristics of parallel resonance.
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State Compensation theorem.
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Give the statement of Millman’s theorem.
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Write short notes on the various losses in dc machine.
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A 230V, dc shunt motor at no load takes a current of 2 Amps. The resistances of armature and shunt field are 0.7Ω and 220Ω respectively. Calculate the efficiency of the motor if the input current is 30 Amps.
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Why are transformers rated in KVA and not in KW?
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Mention few applications of Single phase Induction motor and single phase synchronous generator.
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Part B
Find the current in 12 ohms resistor by using star-delta transformation shown in figure 1.
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State and explain Faraday’s laws of electromagnetic induction.
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Obtain the equivalent resistance between A and B terminals as shown in figure 2.
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Derive the expression for Co-efficient of coupling.
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Deduce the relation between bandwidth and resonant frequency in series resonant RLC circuit.
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An inductive coil takes 10A and dissipates 1000 watts when connected to a supply of 250 V, 25 Hz. Calculate: i) the impedance ii) reactance iii) the inductance iv) power factor. Also, draw the vector diagram.
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A parallel RLC circuit consists of R = 1 kΩ, L = 100 mH, C = 10µF. If a voltage of 100 V is applied across the combination, determine resonant frequency, Q factor and bandwidth.
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State Norton’s theorem. By using Norton’s theorem find the current flowing through (5+j5) ohms impedance shown in figure 3.
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State Maximum Power Transfer Theorem.
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When the load impedance R draws the maximum power? Find the maximum power delivered to the load by using maximum power transfer theorem for the given network shown in figure 4.
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Derive an expression for the emf of DC generator.
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Explain the characteristics of DC Shunt Motors with equations and neat diagrams.
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Explain the construction of DC Generator with a neat diagram and explain the function of each part.
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Sketch the characteristics of DC Series Motors and explain with necessary equations.
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Compare Core type and Shell type 1-ϕ transformers.
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Describe how revolving double field is developed in induction machine?
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Explain the Principle of operation of a single-phase transformer.
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Sketch Torque-slip characteristics of 1-ϕ induction motor. Explain.
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