PDF International Islamic University Chittagong

International Islamic University Chittagong Department of Electrical and Electronic Engineering

B. Sc. Engineering in EEE Final Examination, Spring 2022

Course Code: EEE 1201 Course Title: Electrical Circuits II Full Marks: 50 Time: 2 hours 30 minutes

(i) The figures in the right-hand margin indicate full marks

(ii) Course Outcomes and Bloom's Levels are mentioned in additional Columns Course Outcomes (COs) of the Questions

Reflect a basic understanding of alternating current waveforms, phase shifting, impedance, CLOI power factor, impedance and phasor diagram, circuit theorems for solving series-parallel

~

circuits, poly phase system, magnetic coupling, resonance, and two port network.

Apply complex variable, various circuit rules and theorems for solving complex series CL02

parallel networks.

CL03 Design various series-parallel resonant circuits, passive filters, and two port networks.

Bloom's Levels of the Questions

Letter Symbols R

I

^U

I

^App

I

^An

I

^{E C}

Meaning Remember

I

Understand

I

Apply

I

Analyze

I

Evaluate Create

Q. Part A COs BL M

No. [Answer the questions from the followings]

1. a) Why the maximum voltage across the capacitor lies before the resonance C03 E 5 condition? Give proper explanation in in this regard. Show the plot of VR, VL,

Ve, 1, XL and Xc in terms of capacitance variation for a series RLC resonance circuit.

b) Design a bandpass filter having R, Land

e

in series connection with a lower C03 C 5 cutoff frequency of 20.1 KHz and an upper cutoff frequency of 20.30 KHz.

Consider a suitable value of R in the range of 10 to 20 KQ. Calculate L, C, and Q. Show the response curve for the filter.

Or,

1. a) What are the conditions for series resonance? Show necessary figures to C03

E 5

explain the resonance conditions.

1. b) Design a band reject filter having R, Land

e

in series connection with a C03

C 5

lower cutoff frequency of 20.1 KHz and an upper cutoff frequency of 20.30 KHz. Consider a suitable value of R in the range of 10 to 20 Ki). Calculate L, C, and Q. Show the response curve for the filter.

Page 1 of3

2. a) For the three coupled coils in the following figure (Fig. 1), determine the total COl inductance considering the mutual inductance and the dot conventions.

Ap 5

2H

4H 5H

,-----. r:'>,

o---!-'TH' r~'ffi'----o

6H SH IOH

Fig. 1. Series inductors for finding equivalent inductance for Q. 2. a) ..

2. ^b) What is mutual inductance? Calculate the voltage Vo in the circuit shown in Fig: 2. (X and Yare last two digits of your ID)

J I,

I;:y~j ^{r l}

⁺

OO~ \' ~

fl) X ~ ~ Y

[I

>

IOU

v

. L ^{r I,---~} _t ~

COl Ap 5

Fig. 2 Circuit diagram for the question of 2. b)

PARTB

[Answer the questions from the followings]

3. a)

Discuss the process to find the magnitude of the line current of a l!. connected

generator is

..fj

times the phase current. Explain why it is

..fj

^times.

3. b) Show that the instantaneous power for a three phase system under steady U 5 state condition is independent of time whereas the single phase power has a COl

double-frequency variation with respect to time. Also illustrate the comparison graphically.

Ap 5 COl

4 a) A line voltage of a balance Y-connected source is V AB=240

noD.

If the Ap 5 source is connected to a balanced .6.-connected load and considering each of COl

the load to be 20 L40°

n,

determine the phase and line currents of the system. Assume positive phase sequence.

4 b) The unbalanced .6.-load of Fig, 3 is supplied by a balanced line to line voltage Ap 5 of 240 V in the positive sequence. Determine the line currents. Take Vab as COl

reference.

-- A

0---

--~7'z

lon,if ^t: n

-J5

!.ll~

^'~J6 n

I;,

o---:::___L---

-A/'vVv- --- C

r, /) 16.0

Fig. 3, Part of the network for Questio no 4. b)

Page 2 of3

·_

Or,

4 a) A positive-sequence, balance A-connected source supplies a balance ~- connected load. If the impedance per phase of the load is 18+j 12 Q and la=19.202 U5° A, determine the phase current lAB and phase voltage VAB.

4 b) A unbalance ~- load is connected with a balance Y-connected supply. Where the line voltages are indicated in the figure (Fig. 4). Cosidering a positive sequence and the voltage V ^AB as reference, determine the phase current and line currents for the load. Sketch the phasor diagram for the currents.

2011 100 volts 100 volts

b 61l 81l

b'~~---J

. '~.:~ .. ' .. Fig -. 4_._ .

.e?r.!

of!he netw?r~.fQr Questio no 4. b)

COl

COl

5. a) What is the significance of two port network? What are the essential C03 information we can get from this analysis?

5. b) Determine the current I ^I and h for the following network indicated in Fig. 5.

I I 12

2Q

Z!l =6Q +

ZI2=-j4Q

Z21

=

-)4 Q z22 = 8

n

Fig. 5. Part of the network for Questio no 5 . b)

Page 3 of3

C03

Ap 5

Ap 5

u

5 E 5