GTU BE 1st and 2nd Semester 110005 Elements of Electrical Engineering Summer 2018 Question Paper

1
Seat No.: ________ Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE- SEMESTER ? 1
st
/ 2
nd
(OLD) EXAMINATION ? SUMMER 2018
Subject Code:110005 Date: 28-05-2018
Subject Name: Elements of Electrical Engineering
Time: 02:30 pm to 05:00 pm Total Marks: 70
Instructions:
1. Attempt any five questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
Q.1 (a) State and explain Kirchhoff?s laws. 07
(b) Derive the equation of Star to Delta and Delta to Star transformation. 07

Q.2 (a) Give comparison between electric circuit and magnetic circuit. 07
(b) An iron ring of mean length 1 m has air gap of 1 mm wound with 200 turns.
The relative permeability is 500. If the current flow through coil is 1 A,
calculate flux density.
07

Q.3 (a) Derive the equation of capacitance of parallel plate capacitor with uniform
dielectric medium and with composite dielectric medium.
07
(b) Two capacitors of capacity 2 ?F and 4 ?F are connected in series. A potential
difference of 900 V. Calculate: (i) Voltage across each capacitor (ii) Charge
on each capacitor
07

Q.4 (a) Define (i) Frequency (ii) Peak Factor (iii) Average value (iv) Form factor (v) Power factor (vi) Instantaneous value (vii) Amplitude
07
(b) The following expressions represent the instantaneous values of e.m.f. in
three coils connected in series
e1 = 50 sin ?t
e2 = 40 sin(?t+60?)e3 = 60 sin (?t-30?)Find an expression for the resultant e.m.f.
07

Q.5 (a) Explain series R-L-C circuit with the phasor diagram. 07
(b) Prove that average power consumption in pure inductor is zero when
A.C. voltage is applied.
07

Q.6 (a) Derive the relation between line voltage and phase voltage, line current and
phase current in star connection.
07
(b) What is the construction of three core cable? Explain each parts and its
importance
07

Q.7 (a) Explain charging of battery from AC supply with schematic diagram 07
(b) Explain the working of earth leakage circuit breaker (ELCB) with diagram. 07
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