JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II ELEMENTS OF ELECTRICAL AND ELECTRONICS ENGINEERING Previous Question Paper (September - 2021 - R15)
Answer any five questions. All questions carry equal marks.
Main
Three capacitors of 2µF, 4µF and 6µF are connected in series across 200 V D.C supply. Find the total capacitance, charge and voltage drop across each capacitance. Also, find the energy stored across each capacitor.
Answer
Given capacitors in series: C1 = 2 µF, C2 = 4 µF, C3 = 6 µF, V = 200 V.
Total capacitance (C_eq) is given by:
C_eq = 12/11 ≈ 1.091 µF.
Total charge (Q) = C_eq × V = (12/11) × 10^-6 × 200 ≈ 218.18 µC. Since they are in series, charge on each capacitor is the same: Q1 = Q2 = Q3 = 218.18 µC.
Voltage drops:
Energy stored (E = 0.5 × Q × V):
Explain the principle of operation of DC generator with neat diagram.
Answer
A DC generator operates on the principle of Faraday's Law of Electromagnetic Induction, which states that whenever a conductor cuts magnetic flux, an electromotive force (EMF) is induced in it.
The operation involves:
- A magnetic field is produced by field poles.
- An armature winding is rotated within this field by a mechanical prime mover.
- As the armature conductors cut the magnetic flux, an alternating EMF is induced according to Fleming's Right-Hand Rule.
- A commutator and brush assembly are used to convert this alternating EMF into unidirectional (DC) voltage at the external terminals.
The magnitude of the induced EMF is given by the equation:
where Φ is flux per pole, Z is the total number of armature conductors, N is speed in rpm, P is number of poles, and A is the number of parallel paths.
A 230V DC shunt motor takes 51A full load. Resistances of armature and field Windings are 0.1 ohms and 230 ohms respectively. Determine:
Armature current
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Field current.
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Back emf developed at full load.
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Explain the working principle of transformer with neat diagram.
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A 125 KVA transformer having primary voltage of 2000V at 50 Hz has 182 primary and 40 secondary turns. Neglecting losses. Calculate:
i) The full load primary and secondary currents.
ii) The no load secondary induced emf.
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Explain the principle of operation of alternator with neat diagram.
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Explain the working principle of permanent magnet moving coil instrument with neat diagram.
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Explain the working of attraction type M.I instrument with neat diagram.
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Discuss the behaviour of a P-N junction under forward and reverse biasing.
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Explain how the transistor can be work as amplifier?
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Explain the working principle of CRT with neat diagram.
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