JNTU
JNTU B.Tech II ELEMENTS OF ELECTRICAL AND ELECTRONICS ENGINEERING Previous Question Paper (November/December - 2017 - R15)
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
Explain Kirchhoff’s Laws.
Answer
Kirchhoff's Current Law (KCL) states that the algebraic sum of currents meeting at a junction or node is zero (ΣI = 0). Kirchhoff's Voltage Law (KVL) states that the algebraic sum of all voltages around any closed loop in a circuit is zero (ΣV = 0).
Derive the emf equation of DC generator.
Answer
Let Φ be flux per pole in Webers, P be number of poles, N be speed in rpm, Z be total armature conductors, and A be parallel paths. The emf induced in one conductor is dΦ/dt. For one revolution, time taken is 60/N seconds. Average emf per conductor = ΦP / (60/N) = ΦPN/60. Total emf E = (Average emf per conductor) × (Total conductors / Parallel paths). Thus,
Define voltage regulation of transformer and draw vector diagram of leading and lagging power factor.
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Define slip and write the significance of slip in induction motor.
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Why scale of moving iron instruments is non-uniform while that of PMMC instruments is uniform?
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List the advantages & disadvantages of MI type instruments.
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Define transistor and write different types of transistors.
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Define peak inverse voltage (PIV) and list out the values of PIV for HWR, FWR and Bridge rectifier.
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Write applications of CRO.
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Explain Sensitivity of CRO.
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Part B
Derive expression for delta-star and delta-star transformations.
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The armature of a 2-pole, 220 V Lap wound generator has 400 conductors and runs at 300 rpm. Calculate the useful flux/pole, if the number of turns in each field coil is 1200.
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When running on no load, a 400V shunt motor takes 5A. Armature resistance is 0.5 ohms and field resistance is 200 ohms. Find output of the motor and efficiency when running on full load and taking a current of 50A.
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Explain three point starter, with a neat sketch.
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Explain principle operation of single phase transformer and derive emf equation of transformer.
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Explain synchronous impedance method for regulation of alternator.
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Explain principle of operation of three-phase induction motor.
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Explain slip-torque characteristics of 3-phase induction motor.
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Explain damping techniques used in instruments.
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Explain different types of controlling torques in instruments.
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Explain the construction and working of PMMC instrument with a neat sketch.
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Discuss PN diode with VI characteristics.
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With neat diagrams, explain SCR with its characteristics.
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Explain construction and operation of a Half Wave rectifier and derive its expressions.
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In an NPN transistor if β=50 is used in common emitter circuit with VCC=10V and RC=2KΩ. The bias is obtained by connecting 100KΩ resistor from collector to base. Find the operating point.
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What is CRT and with neat sketch describe the different parts of CRT?
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Explain deflection sensitivity and Deflection factor of a CRO.
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Describe how the following measurements can be made with the use of CRO: i) Phase Angle ii) Frequency.
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Explain Electrostatic and Magnetic deflection instruments.
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