JNTU
JNTU B.Tech II BASIC ELECTRICAL ENGINEERING Previous Question Paper (November/December - 2018 - R13)
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
When three capacitors of 5µF each are connected in series, find its equivalent Capacitance?
Answer
For capacitors connected in series, the equivalent capacitance Ceq is given by 1/Ceq = 1/C1 + 1/C2 + 1/C3. Since all capacitors are 5µF, 1/Ceq = 1/5 + 1/5 + 1/5 = 3/5. Therefore, Ceq = 5/3 = 1.67µF.
State Kirchhoff’s laws with an example.
Answer
Kirchhoff's Current Law (KCL): The algebraic sum of currents meeting at a node is zero. Example: In a junction where 5A enters and 3A and 2A leave, 5 - 3 - 2 = 0.
Kirchhoff's Voltage Law (KVL): The algebraic sum of voltages around any closed loop is zero. Example: In a single loop circuit with a source V and resistors R1 and R2, V - IR1 - IR2 = 0.
Define form factor and peak factor.
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Write the significance of ‘j’ operator in ac circuits.
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What is meant by eddy current losses in a transformer?
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What are the properties of ideal transformer?
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A 3-phase induction motor is wound for 4 poles and is supplied with 415 V, 50 Hz system, Find its synchronous speed.
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What are the difference between long shunt and short shunt DC compound motor.
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Why controlling torque is necessary in an indicating instruments?
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Write the classification of instruments.
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Part B
Discuss the classification of sources in detail.
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State and explain Super position theorem.
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Determine the current flowing through 15 Ω, 30 Ω and 40 Ω resistors if the applied DC voltage is 220 V. Also find power dissipated in 10 Ω resistor shown in figure 1.
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Obtain the relation between star to delta transformation.
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What is a phasor diagram? Develop a phasor diagram for series RL circuit connected across a.c. supply.
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Determine RMS value of the voltage defined by v(t) = 5 sin(314t + π/6).
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Find the average value and form factor of the following voltage waveform shown in figure 2.
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Obtain the phase relations between voltage and current in a pure capacitive circuit excited with 1-ϕ ac supply.
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Discuss the main constructional components of a single phase Transformer.
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Define efficiency and regulation in a Transformer. Give their formulae.
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Discuss the practical transformer on no load condition.
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A 1-ϕ transformer has 500 turns in the primary winding and cross sectional area of the core is 80 cm2 and the primary winding is connected to a 50 Hz, 230 V supply. Calculate maximum flux induced in it.
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Derive the EMF equation of a DC Generator.
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What is the importance of back EMF in a DC machine?
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Describe the principle of operation of 3-ϕ induction motor.
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Explain the following losses in a DC machine: i) Copper losses ii) Iron losses iii) Mechanical Losses.
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Explain the working of PMMC instrument with a neat sketch. Also write its merits and demerits.
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Describe the essential features of measuring instruments.
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Write a short note on damping in measuring systems.
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