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GTU First Year Engineering (Semester 1)
Elements of Electrical Engineering
June 2013
Total marks: --
Total time: --
INSTRUCTIONS
(1) Assume appropriate data and state your reasons
(2) Marks are given to the right of every question
(3) Draw neat diagrams wherever necessary

1 (a) Explain effect of temperature on resistance
3 M
1 (b) Derive equivalent resistances for delta to star transformation.
6 M
1 (c) A 100 V, 100 W lamp is connected in series with a A 100 V, 60 W lamp across 200 V supply. Determine current drawn and power consumed by each lamp.
5 M

2 (a) Draw wiring diagram for staircase wiring.
3 M
2 (b) Derive expression for voltage across capacitor (vc) during charging of capacitor.
6 M
2 (c) Three capacitors having capacitances of 10 μF, 20 μF and 40μF are connected in series to a 400 V d.c. source. Find (i) total capacitance (ii) total charge in circuit (iii) total energy stored.
5 M

3 (a) State similarities between magnetic circuit and electrical circuit
4 M
3 (b) Explain self induced emf and mutually induced emf.
6 M
3 (c) An iron ring has mean diameter of 57.3 cm. It carries a coil having 450 turns and the current flowing through coil is 2 A. The relative permeability of the iron is 1200. Calculate the flux density produced.
4 M

4 (a) Define : (i) Frequency (ii) Average value (iii) power factor.
3 M
4 (b) Prove that current in pure inductive circuit lags its voltage by 90°
6 M
4 (c) Two currents are given by expression: i1=40 sin(314t+30°) and i2=20 sin(314t-60°). Find expression for (i1 - i2).
5 M

5 (a) Explain series resonance circuit. Draw resonance curve.
7 M
5 (b) A coil resistance 15Ω and inductance 0.05 H is connected in parallel with a non-inductive resistance of 20Ω. The circuit is connected across 200 V, 50 Hz supply. Determine (i) current in each branch (ii) total current supplied (ii) power factor of the combination.
7 M

6 (a) Establish relation between line voltage & phase voltage and current relation in 3-phase star connection. Draw phasor diagram.
7 M
6 (b) Explain two wattmeter method for 3-phase power measurement
7 M

7 (a) State types of fuse and explain any one.
4 M
7 (b) Explain different types of lighting schemes.
5 M
7 (c) Explain construction of cable.
5 M

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