Download GTU (Gujarat Technological University Ahmedabad) B.Tech/BE (Bachelor of Technology/ Bachelor of Engineering) 2020 Summer 1st and 2nd Sem 3110005 Basic Electrical Engineering Previous Question Paper
Seat No.: ________
Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE ? SEMESTER 1&2 EXAMINATION ? SUMMER 2020
Subject Code: 3110005 Date:10/11/2020
Subject Name: Basic Electrical Engineering
Time: 10:30 AM TO 01:00 PM
Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
Marks
Q.1 (a) A resistance of 10 is connected in series with two resistances each
03
of the 15 arranged in parallel. What resistance must be shunted
across this parallel combination so that total current taken shall be
1.5 A with 20 V applied?
(b) State the superposition theorem with suitable example.
04
(c) For the Wheatstone bridge diagram shown in Figure 1, obtain the
07
current flowing through the 20 resistance using Thevenin's
equivalent network.
Q.2 (a) Explain Kirchoff's law for DC series network in brief.
03
(b) Define the following terms for AC (alternating current) signal:
04
(i) Crest Factor (ii) Form Fator (iii) Average Value (iv) RMS
Value.
(c) A current of 5 A flows through a non-inductive resistance in series
07
with a choking coil when supplied at 250V,50Hz. If the voltage
across the resistance is 125 V and across the coil 200V, calculate
(i) impedance, reactance and resistance of the coil (ii) the power
absorbed by the coil (iii) and total power.
OR
(c) Prove that the current in purely inductive circuit lags its voltage by
07
90? and average power consumption in pure inductor is zero.
Q.3 (a) Write the comparison between series resonance and parallel
03
resonance condition in AC circuit.
(b) Derive the relation between line-voltage and phase-voltage for
04
three-pha
se four wire star connection network. Also, prove that the
total three-phase power consumption in star connection is PT = 3
VL IL cos .
(c) Explain various connections of three phase transformer with diagram.
07
OR
Q.3 (a) Explain magnetic hysteresis.
03
(b) Derive the E.M.F. equation of a single phase transformer
04
(c) State the difference in core type and shell type transformer with neat
07
and clean construction diagram.
Q.4 (a) How the rotating magnetic field is produce in three-phase induction
03
motor? Explain in brief.
(b) Why single-phase induction motor is not self starting while three-
04
phase induction motor is self starting. Explain in brief.
(c) Explain construction of Alternator with neat diagram.
07
OR
1
Q.4 (a) Justify that how back e.m.f. in DC motor acts like a governor.
03
(b) State the comparison of generator and motor action with respect to
04
design and working principle. Draw the necessary diagram.
(c) Write working principle of DC motor with neat diagram.
07
Q.5 (a) Calculate the resistance of a 100 m length of wire having a uniform
03
cross sectional area of 0.02 mm2 and having resistivity of 40 ?-
cm.
(b) Discuss types of cables used for residential and commercial wiring.
04
(c) Explain the following protective devices in detail:
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(i) SFU (ii) MCB (iii) ELCB
OR
Q.5 (a) A d-c generator has an e.m.f of 200 volts and provides a current of 10
03
amps. How much energy does it provide each minute?
(b) Explain the construction of the lead-acid battery with neat diagram.
04
(c) Explain different types earthing and its importance in electrical
07
utility system in detail.
2
This post was last modified on 04 March 2021