University of Rajshahi
Department of Electrical & Electronic Engineering
B.Sc. Engineering Part-III Odd Semester Examination- 2017
Course Code: EEE 3141
Course Title: Electronic Circuit-III
Time: 3 Hour
Total Marks: 52.5
Notes:
i.
Answer to all parts (a), (b), (c) etc. of a question must be contiguous.
ii.
Use separate answer script for each Section (A/B).
iii.
Right margin indicates the full marks.
Section-A (Answer any THREE set of questions)
1 (a) Define step voltage. Discuss the step voltage response of high pass RC circuit.
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(b) Draw the circuit diagram and response of the low pass RC circuit for (i) pulse input (ii) exponential
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input and (iii) ramp input.
2 (a) Explain diode clipping at different bias levels for both cycles of a sinusoidal input signal with
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appropriate diagrams.
(b) Determine and sketch vo for the following circuit. Consider the diode as Silicon one and R= 1k Ω.
3
R
Vi
+
16 V
Vi
t
0
Vo
+
V
-
4V
-16 V
-
3 (a) Discuss the operation of a basic positive clamper circuit.
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(b) Sketch vo for the following circuit with the input shown. Consider the diode as an ideal one
vi
f = 1000 Hz
C = 1 µF
10 V
0
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+
t1
t2
t3
t4
t
vi
-20 V
T
R
+
V
-
100 kΩ
vo
5V
-
4 (a) Draw the characteristics curve of a tunnel diode and explain it with energy band theory.
(b) Draw the structure of a Triac and explain its operation.
(c) Describe voltage controllable and current controllable negative resistance devices.
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Section-B (Answer any THREE set of questions)
5 (a) Draw a monostable multivibrator circuit.
(b) What determines the output signal’s period and frequency of the monostable multivibrator?
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2
(c) What is rounding? Explain how the rounding distortion is eliminated in astable multivibrator?
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6 (a) What is 555 timer? Explain why normally control terminal of 555 timer is connected to ground
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through a 0.01μF bypass capacitor?
(b) Explain two basic modes in which the 555 timer operates.
7 (a) What are the limitations of OP-AMPS as a comparator?
(b) Draw the circuit diagram of an astable multivibrator and derive the equation for its frequency of
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3
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oscillation.
8 (a) Draw a Schmitt-trigger circuit with transistors and show the operation principle of Schmitt-trigger
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using transfer characteristics.
(b) Write a short note on VCO.
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University of Rajshahi
Department of Electrical & Electronic Engineering
B.Sc. Engineering Part-III Odd Semester Examination- 2017
Course Code: EEE 3143
Time: 3 hours
Course Title: Electrical Machine-III
Full Marks: 52.5
Notes:
i.
Answer to all parts (a), (b), (c) etc. of a question must be contiguous.
ii.
Use separate answer script for each Section (A/B).
iii.
Right margin indicates the full marks.
Section-A (Answer any THREE set of questions)
1 (a) Define distribution factor kd of an alternator.
(b) What is a fractional pitch winding? Why is it used in alternators?
(c) With the help of phasor diagram, explain the effect of load power factor on generated voltage of an
1
2
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alternator.
(d) A six-pole three-phase armature has a total of 432 conductors in 48 slots. The flux per pole is 0.0225
3
webers and has a sine-wave distribution. If the frequency is 50 Hz, find the distribution factor and
generated voltage per phase.
2 (a) What do you mean by armature reaction of an alternator?
(b) Briefly discuss the factors that determine the type of field used for a particular alternator.
(c) Show that, for an alternator the resultant field set up by the currents in the armature remains constant in
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2
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magnitude and rotates at synchronous speed.
(d) A 5-kVA 220-V 60-Hz polyphase alternator is Y-connected. The effective armature resistance per phase
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is 0.60 Ω, and the armature reactance per phase is 3.2 Ω. What is the generated voltage when rated load
is being supplied at (i) unity power factor, (ii) 0.80 lagging power factor, and (iii) 0.85 leading power
factor?
3 (a) Define percent voltage regulation of an alternator.
(b) Give five reasons for placing the armature of an alternator on the stator and the field on the rotor.
(c) Explain the method for determining synchronous impedance of an alternator.
(d) A 1250-kVA 600-V three-phase alternator is tested by means of the open-circuit and short-circuit tests.
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2
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With the rotor revolving at rated speed and the armature short circuited, rated line current flows with a
field excitation of 85 A. With this same dc field current, the open circuit terminal voltage is 250 V. The
average d-c resistance measured across the armature terminals is 0.16 Ω. Calculate the percent voltage
regulation at (i) unity power factor, (ii) 0.80 lagging power factor, and (iii) 0.80 leading power factor.
4 (a) Why synchronization is necessary for parallel operation?
(b) What are the necessity for parallel operation between alternators?
(c) What are the requirements for parallel operation of two alternators? Briefly explain the synchronizing
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2
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procedure between them.
(d) A calibrated shunt motor drives a 1000-kVA 4600-V polyphase alternator at rated speed. With the field
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unexcited, the motor output is 27.2 kW; with rated field excitation, the output is 51.7 kW; with the
armature short-circuited and rated generator line current flowing, the motor output is 60.9 kW; the power
required for the field excitation alone is 13.6 kW. Calculate the overall full-load efficiency of the
alternator at unity power factor.
Section-B (Answer any THREE set of questions)
5 (a) How can synchronous motor be started by reducing the speed of the stator magnetic field?
(b) How does the damper winding of a synchronous motor minimize hunting?
(c) A polyphase synchronous motor has a full load speed of 250 r/min when a 25 Hz supply is applied to
the stator. How many poles does it have?
3
3
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6 (a) Explain how a three-phase synchronous motor can be operated as a variable p.f. load.
(b) What is synchronous condenser? Why is it rated at KVA instead of horse power?
(c) For the preceding 1200 kW 0.60 lagging power factor load, find the KVA rating of a synchronous
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3
condenser required to raise the power factor to 0.90 lagging.
7 (a) What changes are necessary in a series dc motor to adapt it for operating from an ac power source?
(b) Explain the operating principle of a stepper motor.
(c) A stepper motor has a step angle of 2.5 0. Determine the number of steps required for the shaft to move
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3
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25 revolutions.
8 (a) Explain the operating principle of a two-phase AC servomotor.
(b) What mechanism produces the starting torque in a hysteresis motor?
(c) What are the advantages and disadvantages of brushless DC motors compared to ordinary brush DC
motors?
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University of Rajshahi
Department of Electrical & Electronic Engineering
B.Sc. Engineering Part-III Odd Semester Examination- 2017
Course Code: EEE 3145
Course Title: Microprocessor and Microcomputer System
Time: 3 Hours
Total Marks: 52.5
Notes:
i.
Answer to all parts (a), (b), (c) etc. of a question must be contiguous.
ii.
Use separate answer script for each Section (A/B).
iii.
Right margin indicates the full marks.
Section-A (Answer any THREE set of questions)
1 (a) Mention the difference between a microprocessor and a microcomputer.
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(b) Define different units of a microcomputer system.
4
(c) Draw and explain the microcomputer bus structure.
4
2 (a) List the operations that are commonly performed by a microprocessor.
(b) Write about different types of registers in context to 8086 microprocessor.
(c) Draw the flag register of 8085 microprocessor and state the purpose of zero flag.
3 (a) What are the different types of addressing mode used in 8086 microprocessor? Explain them.
(b) Differentiate
between
direct and
indirect addressing. Considering Motorola 680x0
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3
5
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microprocessor, explain the difference between the following two statements:
i) MOVE 99,D1 ii) MOVE #99,D1
4 (a) What are the purposes of RD and ALE signal in microprocessor?
4
(b) Write an assembly language program to evaluate the following:
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a*b+c
(c) What are the differences between a High Level language and Machine Language?
1
Section-B (Answer any THREE set of questions)
5 (a) Define serial IO and parallel IO.
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(b) Differentiate between IO-mapped IO and memory-mapped IO.
3
(c) List the steps involved in DMA transfer.
4
6 (a) What is the major objective for designing a memory system? Explain about the following memory
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device characteristics:
(i)access time (ii) cost
(b) Draw a mapping between a virtual memory and a physical memory.
7 (a) Briefly explain the different modes of operation of 8255 PPI.
(b) Explain the functions of HOLD and HLDA signals.
8 (a) Briefly explain the synchronous and asynchronous data transmission.
(b) Interface a matrix keyboard to a microprocessor.
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4
3
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University of Rajshahi
Department of Electrical & Electronic Engineering
B.Sc. Engineering Part-III Odd Semester Examination- 2017
Course Code: EEE 3149
Time: 3 hours
Course Title: Power Transmission and Distribution
Full Marks: 52.5
Notes:
Answer to all parts (a), (b), (c) etc. of a question must be contiguous.
Use separate answer script for each Section (A/B).
Right margin indicates the full marks.
Section-A (Answer any THREE set of questions)
1 (a) What is an ACSR conductor? Draw the cross section of a 24 AL/7 St conductor.
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(b) Derive the equation of flux linkage of one conductor in a group with proper description.
3
(c) A single circuit with three phase line operated at 60 Hz is arranged as shown in Fig. 1. The
3
conductors are ACSR drake. Find the value of inductive reactance per mile per phase where
Ds = 0.0373 ft.
20'
20'
38'
Fig. 1
2 (a) What is meant by generalized circuit constants of a transmission line? Show that 𝐴𝐷 − 𝐵𝐶 = 1 for
3
short lines.
(b) A short 3-φ transmission line with an impedance of (6 + j8) Ω per phase has sending and receiving
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end voltages of 120 kV and 110 kV respectively for some receiving end load at a p.f. of 0.9 lagging.
Determine the sending end power factor.
(c) What are the various methods of voltage control in a power system?
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3 (a) Define GMD and GMR.
2
(b) Write down the generalized circuit constants of the transmission line with proper configuration.
(c) One circuit of a single-phase transmission line is composed of three solid 0.25 cm radius wires.
3
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The return circuit is composed of two 0.5 m radius wires. The arrangement of conductor is shown
as in Fig. 2. Find the inductance due to the current in each side of the line and the inductance of the
complete line in henry per meter and millihenry per mile.
a
9m
d
6m
b
e
6m
{
c
{
iv.
v.
vi.
Side y
Side x
Fig. 2
4 (a) How does an auto tap-changing transformer work?
(b) What is an induction regulator? Write down the working principle of an induction regulator.
(c) Find the capacitive susceptance per mile for a single-phase line operating at 60 ft. The conductor
is partridge and spacing is 20 ft between centers (outside diameter of partridge = 0.0642 inch).
3
3
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Section-B (Answer any THREE set of questions)
5 (a) Why the consumer having low power factor is charged at higher rates?
(b) Derive an expression for the most economical value of power factor which may be attained by a
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3
consumer.
(c) A 3-φ line having an impedance of (5 + j20) Ω per phase delivers a load of 30 MW at p.f. of 0.8
3
lagging and voltage 33 kV. Determine the capacity of the synchronous condenser required to be
installed at the receiving end if voltage at the sending end is to be maintained at 33 kV.
6 (a) Why are insulators used with overhead lines? Discuss the desirable properties of insulators.
(b) Define and explain string efficiency. Can its value be equal to 100%?
(c) An overhead line has a span of 260 m, the weight of the line conductor is 0.68 kg per meter run.
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3
Calculate the maximum sag in the line. The maximum allowable tension in the line is 1550 kg.
7 (a) What is meant by grading of cables? Why is it required in practice? What are the methods of grading
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of cables?
(b) A single lead sheathed cable is graded by using three dielectrics of relative permittivity 5, 4 and 3
3
respectively. The conductor diameter is 2 cm and overall diameter is 8 cm. If the three dielectrics
are worked at the same maximum stress of 40 kV/cm, find the safe working voltage of the cable.
(c) Compare between overhead transmission line and underground cable. Which is preferred in
3
Bangladesh and why?
8 (a) Show that, the maximum voltage drops in a uniformly loaded distributor fed at both ends with equal
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voltage is IR/8, where the symbols have their usual meanings.
(b) An electric train runs between two substations 6 km apart maintained at voltages 600 V and 590 V
3
respectively and draws a constant current of 300 A while in motion. The track resistance of go and
return path is 0.04 Ω/km. Calculate
i.
The point along the track where minimum potential occurs.
ii.
The current supplied by the two substations when the train is at the point of minimum
potential.
(c) What is corona? How corona effect can be reduced?
2
University of Rajshahi
Session: 2013-2014
Department of Electrical & Electronic Engineering
B.Sc. Engineering Part-III Odd Semester Examination- 2017
Course Code: EEE 3149 Course Title: Electromagnetic Fields and Waves
Time: 3 hours
Notes:
i.
ii.
iii.
Full Marks: 52.5
Answer to all parts (a), (b), (c) etc. of a question must be contiguous.
Use separate answer script for each Section (A/B).
Right margin indicates the full marks.
Section-A (Answer any THREE set of questions)
1 (a) Define “electric scalar potential” and “magnetic vector potential”.
3
(b) Write Maxwell’s equation in differential and integral forms.
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(c) What is displacement current? Write down its significance.
3
2 (a) What are the fundamental properties of the em wave? Find out the velocity of em wave in free space.
(b) Show that the intrinsic impedance of the em wave in free space is equal to 377 Ω.
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3 (a) Find out the attenuation constant, phase constant, intrinsic impedance, phase velocity and wavelength
5
of the em wave in a good conducting medium.
(b) What is Poynting vector? State and explain Poynting theorem.
4 (a)
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

What is uniform plane wave? Prove that a uniform plane wave is transverse in nature and

H
E
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.
(b) What is skin depth? Find out intrinsic impedance and attenuation constant for perfect dielectric.
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Section-B (Answer any THREE set of questions)
5 (a) Define reflection and transmission coefficients. What is the relationship between them? Explain with
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figure.
(b) Show that reflection coefficient, R can be expressed as: -1 < R < 1.
6 (a) State Snell’s law of refraction. Given two mediums having permeabilities µ1 and µ2, prove that,
4
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tan 1 1
, where 1 and 2 represents the angles that the magnetic fields make with the normal

tan  2  2
to the interface in the two mediums.
(b) What do you mean by total reflection? Write down the boundary condition of reflection.
7 (a) What is waveguide? Give examples. Why are rectangular waveguides preferred over circular
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3
waveguides?
(b) Derive the expression for electric and magnetic field components of a rectangular waveguide. Hence
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show that the TEM is not possible in such a wave-guide.
8 (a) Define “gain” and “radiation resistance” of an antenna.
(b) Derive the expression for the radiation pattern of a center-fed /2 dipole antenna. Sketch the radiation
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pattern.
(c) An antenna has a radiation resistance of 720 ohms, a loss resistance of 8 ohms and a power gain of
12 dB. Determine the antenna efficiency and its directivity.
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University of Rajshahi
Department of Electrical & Electronic Engineering
B.Sc. Engineering Part-III Odd Semester Examination- 2017
Course Code: HUM 3141
Course Title: Legal Issues for Engineering and Introduction to
Management
Time: 3 hours
Full Marks: 52.5
Notes:
i.
Answer to all parts (a), (b), (c) etc. of a question must be contiguous.
ii.
Use separate answer script for each Section (A/B).
iii.
Right margin indicates the full marks.
Section-A (Answer any THREE set of questions)
1 (a) What do you mean by contract?
(b) Distinguish between a void agreement and illegal agreement.
(c) “An agreement becomes enforceable by law when it fulfils certain conditions.” Explain those
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5
conditions.
2 (a) When is an offer completed? How and when may an offer be revoked?
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(b) Define the term ‘Acceptance’. What are the essentials of a valid acceptance?
3
(c) What is the difference between a promissory note and bill of exchange?
3
3 (a) Define ‘goods’ and state the different types of ‘goods’.
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(b) Explain the difference between a condition and warranty.
3
(c) Under what circumstances a breach of condition can be treated as a breach of warranty?
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4 (a) Define cheque.
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(b) Explain essential elements of a bill of exchange.
(c) Write short notes on: company, worker, wage and salary.
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3
Section-B (Answer any THREE set of questions)
5 (a) Define management.
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(b) Explain the relationship between management and administration.
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(c) “Authority is transferable, not responsibility”. Explain the statement.
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6 (a) Describe the basic training process.
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(b) Describe and illustrate how you would go about identifying training requirements.
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(c) Explain how to distinguish between problems you can fix with training and those you can’t.
3
7 (a) What do you mean by material Handling?
(b) What are the reasons for using material Handling?
(c) Describe the various principles of material Handling.
8 (a) What is inventory control?
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3
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(b) Discuss briefly the objectives of inventory control.
3
(c) What are the techniques of inventory control?
3