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Biju Patnaik University of Technology BPUT
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B.Tech
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**Electrical and Electronics Engineering**Offline Downloads:
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Subject: BASIC ELECTRICAL ENGINEERING
Subject Code: BE2102
Semester: 2nd 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: J 367
Year of Examination: 2015
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

BASIC ELECTRICAL ENGINEERING –BE2102
Registration No.
Mr. Mitu Baral, ECE,Dept. NIST, Berhampur
:
B.Tech
BE2102
Second Semester Regular Examination-2015
BASIC ELECTRICAL ENGINEERING
BRANCH(S): AEIE, AERO, AUTO, BIOMED, BIOTECH, CIVIL, CSE, EC,
EEE, EIE, ELECTRICAL, ETC, IT, MECH, MINING,
MM, PLASTIC, TEXTILE
QUESTION CODE: J 367
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) Differentiate between an ideal voltage source and practical voltage source?
Answer:
Ideal Voltage source
Practical Voltage source
(i) Its internal resistance is zero.
(i) It has finite value of internal
(ii) Its terminal voltage is constant
and independent of load.
resistance.
(ii) Its terminal voltage depends
upon
load
impedance
hence
terminal voltage does not remain
constant with change in load.
b) Explain the significance of the power factor.
Answer: Power factor is the ratio between active power and apparent power. So it gives
the idea about how much percentage of the total power is utilized for useful work.
NATIONAL INSTITUTE OF SCIENCE &TECHNOLOGY
PALUR HILLS, BERHAMPUR, ORISSA – 761008, INDIA

BASIC ELECTRICAL ENGINEERING –BE2102
Mr. Mitu Baral, ECE,Dept. NIST, Berhampur
c) What do you understand by retentivity?
Answer:
The power of retaining residual magnetism
by a magnetic specimen is called retentivity.
d) Write down the equation of a sinusoidal
source voltage of 60 Hz frequency having
a r.m.s. value of 250V.
Figure 1.c: B- H Curve
Answer:
V (t ) vm sin t
V (t ) 2 250 sin( 2 60)t 354 sin 378t
e) What is the time constant of a RL circuit having R=10Ω and L= 10 H ?
Answer: Time constant for a RL circuit is given by
L 10
1sec
R 10
f) Two impedances of value (2+j6) Ω and (8-j12) Ω are connected in series. What
would be the resulting impedance in polar form?
Solution: let Z1 =2+j6, Z 2=8-j12.
Then the equivalent impedance of for series connection of Z 1 and Z2 is, Z= Z1+Z2
Z= (10-j6) ohms
In rectangular Z=
11.662 30.964 𝝮
g) Describe constant losses occurring in a DC Machine.
Answer:
Iron Losses:
Hysteresis Loss
Eddy Current Loss
Mechanical Losses:
Friction Loss
Windage Loss
NATIONAL INSTITUTE OF SCIENCE &TECHNOLOGY
PALUR HILLS, BERHAMPUR, ORISSA – 761008, INDIA

BASIC ELECTRICAL ENGINEERING –BE2102
Mr. Mitu Baral, ECE,Dept. NIST, Berhampur
h) A 3-Phase, 50 Hz, 415V, six pole induction motor runs at 960rpm. What is the slip
speed and slip?
Answer: Given that,
Ns
P=6, f-50Hz, Vs=415V, Nr=960rpm.
120 f 120 50
1000 rpm
P
6
Slip speed = N s Nr 1000 960 40 rpm
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) A transducer is a physical device which measures physical quantity such as forces,
stresses, temperature, pressure etc.
(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 value 530 Ω, 1060 Ω and
4-j8 Ω are connected in series with a 230 V, 50 Hz supply.
i. Find the total combined impedance in rectangular form?
ii. Magnitude of the current flowing in the circuit?
5 Marks
Solution: Given that:
Z1 530 4.33 j 2.5,
Z 2 1060 5 j8.66,
Z 3 4 j8
i.
The total combined impedance in rectangular form
Z Z1 Z 2 Z3
Z 4.33 j 2.5 5 j8.66 4 j8 13.33 j 3.16
ii.
Magnitude of the current flowing in the circuit
Z 13.33 j3.16 13.7
NATIONAL INSTITUTE OF SCIENCE &TECHNOLOGY
PALUR HILLS, BERHAMPUR, ORISSA – 761008, INDIA

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