JNTU
JNTU B.Tech II ELECTRICAL AND ELECTRONICS ENGINEERING Previous Question Paper (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
Explain the basic circuit components.
Answer
The basic circuit components are resistors, which dissipate energy as heat; inductors, which store energy in a magnetic field; and capacitors, which store energy in an electric field. These are categorized as passive elements.
What are the different types of torques acting on the moving system of measuring instrument?
Answer
The three essential torques acting on the moving system are: 1) Deflecting torque, which moves the pointer from the zero position; 2) Controlling torque, which opposes the deflecting torque to bring the pointer to a steady state; and 3) Damping torque, which prevents oscillations and brings the pointer to rest quickly.
Mention the parts of a DC Machine.
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What is the need for starter in a motor?
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Write the properties of ideal transformer.
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Define slip and slip speed of a 3-φ Induction motor.
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Draw the V-I characteristics of SCR.
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Distinguish between PNP and NPN junction transistors.
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Define deflection and sensitivity.
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How frequency can be measured using CRO?
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Part B
State and explain Kirchoff’s laws.
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A 20mH coil is connected in series with another coil of same value. The total inductance is 80mH. Find the inductance of the second coil, mutual inductance and coefficient of coupling. Derive the expression used.
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Find the equivalent resistance across AB, in the circuit shown in figure. All the resistances are equal to 6Ω.
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Describe the moving coil permanent magnet instrument with neat circuit diagram.
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Explain the constructional details and working of a DC Generator with neat sketch.
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Derive the torque expression of a DC motor.
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A 220V DC shunt motor takes a total current of 90A and runs at 700 rpm. The resistance of the armature winding and shunt field winding is 0.1 ohms and 40 ohms respectively. Find the torque developed by the armature.
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Derive the induced e.m.f equation of transformer.
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The full load copper and iron losses of a 20KVA, 1-ϕ transformer are 350W and 150W respectively. Calculate the efficiency on: i) full load ii) half load when load power factor is 0.8 lagging in each case.
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Discuss the principle of operation 3-phase induction motor.
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Explain the synchronous impedance method of computing the voltage regulation of an alternator.
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What is a PN junction diode? Draw its V-I characteristics when it is: i) forward biased ii) reverse biased.
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Explain how is a transistor used as an amplifier?
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Describe the operation of PNP junction transistor.
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Draw the basic structure of a SCR and explain its working.
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Describe how voltage and current can be measured using a CRO.
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An electrostatic cathode ray tube has a final anode voltage of 500V. The deflection plates are 4cm long and 2cm apart. The screen is at a distance of 10cm from the centre of plates. A voltage of 20 V is applied to the deflection plates. Calculate: i) Velocity of electron on reaching the field ii) Acceleration due to deflection field. iii) Deflection produced on the screen in cm and iv) Deflection sensitivity in cm/V.
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Draw and explain the construction of CRT.
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How can the phase difference between two AC voltages be measured by a CRO?
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