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Solution to Previous Year Exam Questions pyq for Basic Electrical Engineering - BEE of 2014 - bput by Mitu Baral

  • Basic Electrical Engineering - BEE
  • 2014
  • PYQ Solution
  • Biju Patnaik University of Technology Rourkela Odisha - BPUT
  • Electronics and Communication Engineering
  • B.Tech
  • 70 Offline Downloads
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Subject: BASIC ELECTRICAL ENGINEERING Subject Code: BE2102 Semester: 1st SEMSTER Applicable Branch (es): AEIE,AERO,AUTO,BIOTECH,CHEM,CIVIL,CSE,EC, EEE,EIE,ELECTRICAL,ENC,FASHION,FAT,ETC,IEE,IT,MANUFACT,MANUTECH, MECH,MINERAL,MINING,MM,MME,PLASTIC,TEXTILE Question Code: H 456 Year of Examination: 2014 Exam Type: (Special/Regular/Back): Regular Examination Solution Prepared by Sl. No. 1 Faculty Name Mitu Baral Email ID mitubaral@gmail.com NATIONAL INSTITUTE OF SCIENCE &TECHNOLOGY PALUR HILLS, BERHAMPUR, ORISSA – 761008, INDIA

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Mr. Mitu Baral, ECE,Dept. NIST, Berhampur. BASIC ELECTRICAL ENGINEERING –BE2102 Registration No. : B.Tech BE2102 First Semester Back Examination-2014 BASIC ELECTRICAL ENGINEERING BRANCH(S): AEIE,AERO,AUTO,BIOTECH,CHEM,CIVIL,CSE,EC, EEE,EIE,ELECTRICAL,ENC,FASHION,FAT,ETC,IEE,IT, MANUFACT,MANUTECH, MECH,MINERAL,MINING, MM,MME,PLASTIC,TEXTILE QUESTION CODE: L 354 Full Marks – 70 Time: 3 Hours Answer question No. 1 which is compulsory and any five from the rest The figures in the right – hand margin indicate marks 1. Answer the following question: 2 X10 a) Define an ideal voltage source? (i) A voltage source that maintains constant terminal voltage irrespective of variations in load current is called as ideal voltage source. (ii) For ideal voltage source, internal resistance doesn’t exist and may be treated as zero. Where, E- Source emf , V- Terminal voltage b) How Controlled current source is different from other independent source? Answer: (i) A controlled current source depends on some other quantity in the circuit which may be either a voltage or current. Such a source is represented by a diamond shaped symbol. (ii) An independent source is one which do not depend on any other quantity in the circuit. (iii) There are two types of controlled current sources. (a) Voltage Dependent Current Source (VDCS) NATIONAL INSTITUTE OF SCIENCE &TECHNOLOGY PALUR HILLS, BERHAMPUR, ORISSA – 761008, INDIA

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BASIC ELECTRICAL ENGINEERING –BE2102 Mr. Mitu Baral, ECE,Dept. NIST, Berhampur. (b) Current Dependent Current Source (CDCS) c) Explain briefly residual magnetism and it’s reason? Answer: (i) The magnetism remaining in the magnetic material, even when the magnetizing field is reduced to zero is called residual magnetism. (ii)The reasons for residual magnetism for ferromagnetic materials are welding, Figure 1.c: B- H Curve bending, drilling, erosion, some type of induction, induced magnetism caused by machining etc d) For a single phase AC voltage write down the relationship among peak value, r.m.s. value and the average value. Answer: For a single phase AC voltage source RMS value= (Peak value)/ 2 (for sinusoidal a.c.) RMS value= Average value  Form Factor e) What is the time constant of a RC circuit having R=10𝝮 and C=10µF? Answer: Time constant of a RC circuit is given by, ζ =RC= 10 × 10 × 10-6= 10-4 sec f) In a circuit the voltage and current equations are given by V= 15sin (⍵t+300) and I= 15sin (⍵t-300). Find the power consumed in the circuit. Answer: V= 15sin (⍵t+300) and I= 15sin (⍵t-300) Power consumed (P) = Vrms Irms cos⏀ = (15/ 2 ) (15/ 2 ) cos600= 56.25 watt (since⏀=300-(-300) = 600) g) Describe various losses occurring in a DC machine. Answer: The losses in a DC machine consist of NATIONAL INSTITUTE OF SCIENCE &TECHNOLOGY PALUR HILLS, BERHAMPUR, ORISSA – 761008, INDIA

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BASIC ELECTRICAL ENGINEERING –BE2102 Mr. Mitu Baral, ECE,Dept. NIST, Berhampur. (i) Copper losses :- Armature copper loss, shunt field copper loss, series field copper loss (ii) Magnetic losses:- Hysteresis loss, eddy current loss (iii) Mechanical losses:- Frictional loss at the bearings & commutator, brush frictional loss, air frictional loss due to rotating armature. h) Find the probable number of poles of an induction motor having no load speed of 1750rpm when supplied from a three phase 60Hz supply. Answer: Ns=1750rpm, f= 60 Hz We now, Ns=120f/P  P  120 f 120  60   4.114  4 Ns 1750 Hence probable number of poles=4 i) What is noise and write various sources of noise? Answer: (i) Any undesirable signal interfering with measurement is known as noise. (ii) The various sources of noise in measurement are the electromagnetic fields caused by fluorescent light fixtures, video monitors, power supplies, switching circuits and high voltage or current circuits. j) What is a transducer? Answer: (i) Transducer is a physical device which measures physical quantity such as forces, stresses, temperature, and pressure. (ii)A transducer converts the change of a physical quantity (eg: humidity, pressure) to a corresponding change in an electrical quantity (eg: voltage or current). 2 a) In an AC single phase circuit, three impedances of values 5  300𝝮, 3+j6 𝝮 and 4-j8𝝮 are connected in series with a 230V, 50Hz supply. (i) Find the total combined impedance in polar form. (ii) Magnitude of the current flowing in the circuit. [5] NATIONAL INSTITUTE OF SCIENCE &TECHNOLOGY PALUR HILLS, BERHAMPUR, ORISSA – 761008, INDIA

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