Gujarat Technological University 2009 B.E Elements of electrical engineering-110005 ch- - Question Paper
GUJARAT TECHNOLOGICAL UNIVERSITY
B.E. Sem-I Remedial examination March 2009
Seat No. Enrolment No.
Subject code: 110005 Subject Name: Elements of Electrical Engineering.
Date: 19 / 03 /2009 Time: 02:00pm To 04:30pm
Instructions: Total Marks: 70
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
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Q1. (A) |
Derive an expression for the capacitance of a parallel plate capacitor with plate area A and distance of separation between the plates d in M.K.S. |
(07) |
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(B) |
Two capacitors having 8 F and 4 F are connected in series and charged from a constant voltage of 210 Volts supply. Calculate (a) The voltage across each capacitor (b) The charge on each capacitor. |
(07) |
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OR | ||
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(B) |
A capacitor of 10 F is connected to a DC supply through a resistance of 1.1 MQ. Calculate the time taken for the capacitor to reach 90 % of its final charge. |
(07) |
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Q2(A) |
Prove that if a DC current of I amperes is super-imposed in a conductor by an AC current of maximum value I amperes, the root mean square (rms) value of the resultant is (V3/V2)I. |
(07) |
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(B) |
Two branches numbered 1 and 2 having impedances of 3 + j4 Q and 3 -j4 Q respectively are connected to a 230 Volt, 50 Hz rms source. Find out : (i) The total current drawn from the source. (ii) Power factor of that current. (iii) Draw the phasor diagram for I1, I2, the total current and supply voltage. |
(07) |
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Q3( A) |
State and explain Kirchoffs voltage and current laws. |
(05) |
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(B) |
Draw Wheatstones bridge network ABCD as follows: Resistance between terminals A-B, B-C, C-D, D-A and B-D are 10, 30, 15, 20 and 40 ohms respectively. A 2 volt battery of negligible resistance is connected between terminals A and C. Determine the value and direction of the current in the 40 Q resistor. |
(05) |
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(C) |
Show that Rt= Ro(1 + a t) . Notations have usual meaning. The resistance of tungsten filament of a lamp is 20 Q at the room temperature of 20 C. What is the operating temperature of the |
(04) |
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filament if the resistance temperature co-efficient of tungsten is 0.005/ C at 20 C. The base of the lamp is marked 120 Volt, 50 W. | ||
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OR | ||
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Q3 (A) |
Draw the circuit diagram of tubelight with the wiring of choke and starter. Explain the functioning of the circuit. |
(05) |
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(B) |
Explain the biological effect of electric current keeping the electric safety in view. Explain plate earthing. |
(05) |
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(C) |
Sketch the staircase wiring. |
(04) |
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Q4 (A) |
Give the comparison between electric and magnetic circuit. |
(05) |
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(B) |
Give the comparison of series resonance and parallel resonance. |
(05) |
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(C) |
State and explain Faradays laws of electromagnetic induction. |
(04) |
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OR | ||
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Q4 (A) |
Two coils having 100 and 1000 turns respectively have a common magnetic circuit of 25 cm. diameter and 625 cm2 cross-section and a constant relative permeability of 2000. Calculate (i) The self inductance of both the coils. (ii)The mutual inductance between them if the co-efficient of coupling is 0.5. |
(07) |
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(B) |
Write down the line value and phase value relationship of voltages and currents in 3 phase star and delta connected systems. |
(07) |
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Q5 (A) |
Draw and explain the wiring diagram of supply mains with energy meter and distribution box. |
(07) |
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(B) |
Give the circuit diagram of ELCB. Explain its working in brief. |
(07) |
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OR | ||
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Q5 (A) |
Explain the construction and working of any type of battery you know. What is its voltage when it is fully charged ? |
(07) |
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(B) |
The input power to a 3 phase load is measured by two wattmeter method. The ratio of the readings of the two wattmeters connected for 3 phase balanced load is 4:1. The load is inductive. Find the load power factor. |
(07) |
2
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Attachment: |
| Earning: Approval pending. |
