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:

**07**

(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.

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This post was last modified on 04 March 2021