West Bengal Institute of Technology (WBIT) 2010 B.Tech Semester 1 - BASIC ELECTRICAL AND ELECTRONICS ENGINEERING -1 - Question Paper
West Bengal University of Technology (WBUT)
FIRST SEMESTER B.TECH. exam
10 DECEMBER 2010
BASIC ELECTRICAL AND ELECTRONICS ENGINEERING - one (SUBJECT CODE: HU-101)
Time: three hours Max. Marks: 70
Name :
RoUNo.:..................................................................
Invigilator's Signature ......................................
CS/B.TECH (NEW)/SEM-1/ES-101/2010-11 2010-11
BASIC ELECTRICAL & ELECTRONICS ENGINEERING-I
Time Allotted : 3 Hours Full Marks : 70
THIS QUESTION BOOKLET CONSISTS OF 2 PARTS PART I & PART II.
TO ANSWER THE QUESTIONS USE SEPARATE ANSWER BOOKS FOR SEPARATE PARTS.
DO NOT ANSWER BOTH THE PARTS IN THE SAME ANSWER-BOOK.
The figures in the margin indicate full marks.
Candidates are required to give their answers in their own words
as far as practicable.
PART - I ( Marks : 35 )
GROUP - A ( Multiple Choice Type Questions )
1. Choose the correct alternatives for any five of the following :
5x1=5
i) The form factor of a wave is 1. Its shape is a) sinusoidal b) triangular
c) square d) sawtooth.
ii) The admittance of a parallel circuit is 0-5 Z - 30. The circuit is
a) inductive b) capacitive
c) resistive d) in resonance.
iii) The force experienced by a small conductor of length L, carrying a current I, placed in a magnetic field B* at an angle 0 with respect to B* is given by
a) BIL b) BIL sin 0
c) BIL cos 0 d) zero.
iv) The mutual inductance between two coupled coils is 10 mH. If turns of one coil are doubled and that in other are halved, the mutual inductance will be
a) 5 mH b) 10 mH
c) 14 mH d) 20 mH.
v) Three resistors of 4 Q, 6 Q and 8 2 are connected in
parallel. The maximum power dissipation will occur in
- i
a) 4 Q b) 6 Q
c) 8(2 d) equal in all resistors.
a) 5 V, lOfl b) 10 V, 10 Q
vi) For the circuit shown, the Thevenins voltage and resistance as seen at ab Eire
c) 5 V, 5 Q d) 15 V, 15 Q.
GROUP -B ( Short Answer Type Questions )
Answer any two of the following. 2x5= 10
2. State and prove maximum power transfer theorem.
3. Compare electric and magnetic circuits with respect to their similarities and dissimilarities.
4. What is resonance ? Deduce the expression of frequency in a series RLC circuit at resonance.
5. At t = 0, the instantaneous value of a 50 Hz, sinusoidal current is 5 Amp and increases in magnitude further. Its R.M.S. value is 10 Amp.
a) Write the expression for its instantaneous value
i
b) Find the current at t= 0-01 and t = 0-015 sec
c) Sketch the waveform indicating these values.
GROUP -C ( Long Answer Type Questions )
CS/B.TECH (NEW)/SEM-1/ES-101/2010-11
Answer any two of the following. 2x10 = 20
6. a) For the circuit shown below, determine the current 11 , l2 , l3 using nodal analysis : ,
b) For the circuit shown below, find the potential difference between a and d :
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S'S*- |
6 + 4
Explain what are meant by phase and phase difference of sinusoidal waves.
a)
b)
7.
A coil of resistance 30 Q and inductance 320 mH is connected in parallel to a circuit consisting of 75 Q in series with 150 yiF capacitor. The circuit is connected to a 200 volt, 50 Hz supply. Determine supply current and circuit power factor. 2 + 8
8. 0 State and explain Biot-Savart law.
b) A ring having a mean diameter of 21 cm and a crosssection of 10 cm 2 is made of two semicircular sections of cast iron and cast steel respectively with each joint having reluctance equal to air gap of 0-2 mm as shown in figure. Determine the ampere turns required to produce a flux of 0-8 mWb. The relative permeabilities of cast iron and cast steel are 166 and 800 respectively. Neglect fringing and leakage effects. 4 + 6
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Cast steel |
9. a) Prove that current in purely resistive circuit is in phase with applied A.C. voltage and current in purely capacitive circuit leads applied voltage by 90 and draw their waveforms.
b) A circuit consists of series combination of elements as reistance of 6 2, inductance of 0-4 M and a variable capacitor across 100 V, 50 Hz supply. Calculate
(i) value of capacitance at resonance, (ii) voltage drop across capacitor and (iii) Q factor of coil. 5 + 5
USE SEPARATE ANSWER-BOOK TO ANSWER PART-II QUESTIONS. PART - II ( Marks : 35 ) GROUP - A ( Multiple Choice Type Questions )
1. Choose the correct alternatives for any five of the following :
5x1=5
i) Barrier potential of Ge diode is
a) 0-3 V b) 0-7 V
c) 04 V d) 0 V.
ii) With both junctions reverse biased the transistor operates in
a) active region b) cut-off region
c) saturation region d) inverted region.
ill) If a resistor has the colour code ( brown-black-red ), the value of the resistor equals
a) 1000 Q b) 10 k2
c) 110 Q d) 100 Q.
iv) For full-wave rectifier
a) one centre-tapped transformer is required
b) two centre-tapped transformers are required
c) more than two centre-tapped transformers are required
d) centre-tapped transformer is not required.
v) X has high current, voltage, power gain. X is
a) CE amplifier b) CB amplifier
d) none of these.
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c) CC amplifier d) vi) a and P of a BJT are related as |
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b) d) |  |
GROUP -B ( Short Answer Type Questions )
Answer any two of the following. 2x5= 10
2. Differentiate between Avalanche and Zener breakdowns.
3. a) Explain with appropriate diagram why a semiconductor
acts as an insulator at about O K and why its conductivity increases with increasing temperature.
b) If a donor type of impurity is added to the extent of one
atom in 10 million Ge atoms, calculate the resistivity and conductivity of the N-type material so formed. What is the percentage of increase in the conductivity compared to the intrinsic Ge at 399 K. Given at 300 K, atoms/m 3 of Ge = 4-4 x 10 28 , Ni = 2 5 x 10 19, p = 0-38 m 2/V-s, p = 0-18 m 2/V-s. 2 + 3
4. Compare two types of full-wave recitifier :
a) Centre tapped transformer
b) Bridge type.
5. Find the values of (i) IB , (ii) IE , (iii) V CE , (iv) V E and V B for the following circuit. Assume (3 = 49 and VBE = 0-7 V.
GROUP-C ( Long Answer Type Questions )
Answer any two of tJie following. 2 x 10 = 20
6. a) What is thermal runaway ? Can we interchange the
emitter and collector of a transistor ? In what region of the characteristic curve does a transistor operate when it is used as a switch. 4 + 3+1
b) What do you mean by load line for a transistor circuit ?
2
7. Define h-parameters used in hybrid model of transistor with diagram. Compare the characteristics of CE, CC and CB transistors. 6 + 4
8. a) Explain the principle of n-channel depletion MOSFET.
b) Write a short note on CMOS. 6 + 4
9. Write short notes oh any two of the following : 2x5
i) Clipper circuit
ii) Ripple factor 1
iii) Varactor diode.
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Attachment: |
| Earning: Approval pending. |
