JNTU
JNTU B.Tech II ELECTRICAL AND ELECTRONICS ENGINEERING Previous Question Paper (May - 2019 - 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
What is meant by linear and nonlinear elements? Give one example for each.
Answer
A linear element is one whose V-I characteristics are a straight line passing through the origin, obeying Ohm's Law (e.g., a resistor). A nonlinear element is one whose V-I characteristics are not a straight line, meaning its parameters change with voltage or current (e.g., a p-n junction diode).
Present the expression for deflection in a MI instrument. Why the MI meter has non uniform scale?
Answer
The deflection torque in a Moving Iron (MI) instrument is given by:
The scale is non-uniform because the deflection torque is proportional to the square of the current (I2), resulting in a square-law scale that is cramped at the beginning and expanded at the higher end.
What is the difference between Lap winding and Wave Winding of a DC Machine armature.
Answer
Sign in to view the complete answer paper.
State the function of No-volt coil of the starter.
Answer
Sign in to view the complete answer paper.
Does transformer draw any current when secondary is open? Why?
Answer
Sign in to view the complete answer paper.
Mention the differences between salient pole and non salient pole synchronous machine.
Answer
Sign in to view the complete answer paper.
Sketch the voltage versus current graph for p-n junction diode.
Answer
Sign in to view the complete answer paper.
How does current increase in the transistor when breakdown occurs due to avalanche multiplication?
Answer
Sign in to view the complete answer paper.
List out the applications of CRO.
Answer
Sign in to view the complete answer paper.
What is meant by deflection and sensitivity of a CRO?
Answer
Sign in to view the complete answer paper.
Part B
State Ohm’s law and define resistance. How do you express ohm’s law in terms of conductance? Can we apply Ohm’s law in any electrical circuit?
Answer
Sign in to view the complete answer paper.
Find the resistance between terminals XY of the bridge circuit shown in Figure by using delta-star transformations.
Answer
Sign in to view the complete answer paper.
State the advantages and disadvantages of PMMC instrument.
Answer
Sign in to view the complete answer paper.
Three equal resistors each of R ohms are connected in star. Derive the value of resistors in the equivalent delta.
Answer
Sign in to view the complete answer paper.
Derive from the fundamental, torque equation of DC motor.
Answer
Sign in to view the complete answer paper.
A long shunt dc generator delivers a load current of 120A at 320V. The resistance of the armature, series and shunt fields are 0.15 Ω, 0.05 Ω and 125 Ω. Calculate the emf induced in the armature. Allow a brush contact drop of 2V.
Answer
Sign in to view the complete answer paper.
What is the necessity of starter in a DC motor? Explain the working principle of 3-point starter with a neat sketch.
Answer
Sign in to view the complete answer paper.
A 6-pole DC generator has 150 slots. Each slot has 8 conductors and each conductor has resistance of 0.01Ω. The armature terminal current is 15 A. Calculate the current per conductor and the drop in armature for Lap and Wave winding connections.
Answer
Sign in to view the complete answer paper.
Discuss the constructional details of synchronous machine.
Answer
Sign in to view the complete answer paper.
In a 6-poles, 3-phase, 50Hz induction motor with star-connected rotor, the rotor resistance is 0.25Ω/ph, the reactance at standstill is 1.25 Ω/ph, and an emf between the slip-rings on open-circuit is 15V. Calculate slip at a speed of 900 rpm and rotor frequency and reactance at a speed of 900 rpm.
Answer
Sign in to view the complete answer paper.
Describe briefly various losses in a transformer and also obtain the condition for maximum efficiency.
Answer
Sign in to view the complete answer paper.
Draw the slip-torque characteristics of 3-phase induction motor.
Answer
Sign in to view the complete answer paper.
How does the reverse saturation current in a PN junction diode vary with temperature?
Answer
Sign in to view the complete answer paper.
List out the basic transistor configurations and obtain the interrelationship between the current gains in any one.
Answer
Sign in to view the complete answer paper.
What is a p-n junction? How is a potential barrier formed in it?
Answer
Sign in to view the complete answer paper.
Draw the equivalent circuit of NPN transistor along with its output characteristics.
Answer
Sign in to view the complete answer paper.
How is the phase difference between two signals measured with the help of CRO? Explain.
Answer
Sign in to view the complete answer paper.
What is CRT? How it is used? Distinguish between a CRT and a CRO.
Answer
Sign in to view the complete answer paper.
Derive the expression for the vertical deflection on the screen of a cathode ray tube in terms of length of plates, separation distance, accelerating voltage and distance of screen from the origin.
Answer
Sign in to view the complete answer paper.