Assessment Details and Submission Guidelines
School SITE
Course Name Bachelor of Engineering (Telecommunication)
Unit Code BE104
Unit Title Electrical Circuit Fundamentals
Assessment Author
Assessment Type Individual
Assessment Title Assignment 2
Unit Learning Outcomes covered in this assessment a)
b) Describe basic electrical circuits and circuit elements schematically and analytically, and analyse their steady states using phasor diagrams, including their voltage-current characteristics.
Apply electrical circuit laws to calculate currents, voltages and powers in linear and nonlinear AC and DC electrical circuits using a variety of analytical methods.
d) Simp lify complicated electrical circuits into their equivalent Thevenin and Norton circuits.
e) Design and simulate basic electrical circuits using software.
f) Write laboratory reports on experiments in a professional manner.
g) Understand basic electrical quantities and their units, as well as the relationships between them.
Weight 30%
Total Marks 220
Final Marks = Total Marks x SPARKPLUS RPF Factor
Word/page limit N/A
Release Date Week 6
Due Date Report, Week 11, Tuesday, 2/6/2020, 23:55
Demonstration, Week 11, Tuesday, 2/6/2020, 15:30
Submission Guidelines All work must be submitted on Moodle by the due date along with a completed Assignment Cover Page.
Students need to submit an assignment file and simulation file in Moodle submission link.
SPARKPLUS Self & Peer Assessment and Feedback for group assignment is a compulsory task for each student. The SPARKPLUS results will determine the final assignment mark.
The assignment must be in MS Word format, 1.5 spacing, 11-pt Calibri (Body) font and 2 cm margins on all four sides of your page with appropriate section headings.
Reference sources must be cited in the text of the report, and listed appropriately at the end in a reference list using the IEEE referencing style.
Students must ensure before submission of final version of the assignment that the similarity percentage as computed by Turnitin has to be less than 10%. Assignments with more than 10% similarity may not be considered for marking.
Late submission penalty: a penalty of 10% (of total available marks) per day, 0% score for more than 5 days late submission.
April, 2020

This assignment is a group assignment. Students will work in max groups of three and only the group leader will submit the files required at Moodle assignment submission link. Note that the groups will be created randomly. Contribution of each member must be included in the report.
SPARKPLUS is Self & Peer Assessment and Feedback for group assignment. It is an individual and compulsory task for each student. Student who does not use SPARKPLUS will have 0 mark for the assignment.
SPARKPLUS RPF factor is a value between 0 and 1 which will determine the final assignment mark. This factor is generated by the SPARKPLUS website as soon as the group members do the SPARKPLUS review task. Please read Student’s SPARKPLUS Guideline in the assignment folder for how to use it.

Question 1: [4 marks x 5 = 20 marks]
Briefly explain your understanding of what an op-amp is, including how it operates.
Do a research of 741 op-amp, then state two manufacturer vendors of it and their popular applications. Read the specification, explain what is the open-loop amplifier and close-loop amplifier in your own words and find what the maximum voltage can supply to the op-amp.
Circuit shown in Figure 1 contains an op-amp, resistor R1 and R2 as one of its elements. Student will select the value of resistor in Table 1 regarding their group number.
Compute the closed-loop gain v0/vs.
Find the current i if vs = 3V.
Construct the circuit of question (c) in LTspice. Measure the gain and find the current i by the simulation in LTspice. Note that the op-amp needs ± 12V DC power supply and you can use LT1001 op-amps model.
Consider applying the 2V peak-to-peak sinewave and frequency 1KHz to the input (vs) of op-amp, plot the output v0 and explain the reason why you get that result.

Figure 1 Circuit for Question 1

Table 1 Resistors

Group R1 R2
1 1 kΩ 3 kΩ
2 10 kΩ 20 kΩ
3 1.5 kΩ 3 kΩ
4 25 kΩ 50 kΩ
5 10 kΩ 30 kΩ
6 2 kΩ 4 kΩ

Question 2: [10+5+5 = 20 marks]
You have been given to design the engineering application for controlling the water flow from two streams. Assume that the flows of stream are measured as v1 and v2 and both can be calculated as the following operation. Note that student will select the operation in Table 2 regarding their group number

Group vo
1 4v1 – 2v2
2 5v1 + 2v2
3 -3v1 + 4v2
4 -3v1 – 2v2
5 3v1 – 1.5v2
6 3v1 – 2v2

Using two op-amp and variety of resistors (from 1kΩ to 100kΩ), design the circuit to perform the operation. Explain in detail how you design it.
Construct the circuit of question (a) in LTspice. Make sure you select the suitable voltage supply for the circuit
Consider in the normal day and rain day, the stream velocity flows as the following waveform:
Normal day
v1 as the 10 mV peak-to-peak sinewave and frequency 1KHz
v2 as the 20 mV peak-to-peak sinewave and frequency 2KHz
Rain day
v1 as the 1V peak-to-peak sinewave and frequency 100KHz
v2 as the 2V peak-to-peak sinewave and frequency 300KHz
Simulate the results in LTspice and explain the reason why you get that result?

Question 3: [5 +5+10 marks = 20 marks]
Describe the meaning of a passive electrical circuit.
Describe the differences between capacitor, inductor and resistor. Include in your description their current-voltage relationships, impedances and admittances.
Figure 2 shows the voltage across a capacitor of capacitance 300 µF, time is measured in msec.
Determine the mathematical formula for the current flowing through the capacitor.
Plot the current waveform across the time.
Compare the energy stored in the capacitor at the times t = 1 ms and t = 4 ms.
Draw the phasor diagrams for the voltage across and the current flowing through the capacitor.

Figure 2 Voltage waveform across a capacitor.

Question 4 [5 marks x 4 = 20 marks]
Consider the circuit in Figure 3, the current 𝑖(𝑡) = 50 sin(120𝜋𝑡) 𝑚𝐴 pass through a 10 mH inductor.
Compute the voltage across the inductor.
Compute the energy stored in the inductor.
Draw the phasor diagrams for the voltage across and the current flowing through the inductor.
Using LTspice, model the current source through the inductor above and plot the voltage and current waveform across the inductor. Hint: to model current source, you need to find the frequency (Hertz) first.

Figure 3 Current source across an inductor

Question 5 [10 marks x 2 = 20 marks]
A simple relaxation oscillator circuit is shown in Figure 4. The neon lamp fires when its voltage reaches 75 V and turns off when its voltage drops to 30 V. Its resistance is 120 Ω when on and infinitely high when off.
(a) For how long is the lamp on each time the capacitor discharges? (b) What is the time interval between light flashes?

Figure 4: RC relay circuit for Neon lamp

Question 6 [5 marks x 4 = 20 marks]
Consider the circuit of Figure 5. Assume that the switch is closed at time t=0. Noting that u(-t)=1, t<0; and u(-t)=0, t>0; and u(-t)=1-u(t), compute and plot:
(a) List the solution to find the transient response and steady-state response (b) i(t) for all time.
v(t) for all time.
Analyse the steady-state of the circuit using phasor diagram.
Use LTSpice, a computer software used for the analysis of electric circuits, to find the voltages at the nodes of the circuit in Figure 5 when the switch is closed.

Figure 5: Circuit for Question 6

Question 7 [4 marks x 5 = 20 marks]
Consider the two AC voltages 𝑣1(𝑡) = 20 sin(60𝜋𝑡 + 60𝑜) and 𝑣2(𝑡) = 60 𝑐𝑜𝑠(60𝜋𝑡 − 10𝑜).
Compute the:
Amplitude of each of voltages.
Phase in degrees and radians of each of voltages.
Period of each of voltages.
Angular frequency in rad/s and the frequency in Hertz of each of voltages.
Using MATLAB, plot the two waveforms v1(t) and v2(t) then:
Find the phase angle between the two waveforms.
State which of the waves is leading the other.

Question 8 [5 marks x 4 = 20 marks]
A complex number is given in its polar form as 𝑋 = 8∠40𝑜 and 𝑌 = 10∠30𝑜.
Rewrite this number in its equivalent:
Rectangular form.
Exponential form.
Evaluate the following quatities and express the results in polar form:
In the 2-dimensional complex plane, sketch your results of parts (b).

Question 9 [4 marks x 5 = 20 marks]
A circuit contains a capacitor with capacitance C=20 µF and an inductor of inductance L=200 mH.
These two electrical elements are connected in parallel.
The circuit is excited with the voltage 𝑣(𝑡) = 10 sin(500𝑡 + 60𝑜).

Sketch and label the electrical circuit.
Express v(t) and all the electrical elements in phasor form.
Compute the current passing through the inductor and capacitor.
Draw the phasor diagram of the capacitor and the phasor diagram of the inductor.
Using LTspice, model the electrical circuit above and plot the voltage and current waveform across the inductor. (Hint: to model current source, you can find the frequency in Hertz first).

Peer evaluation:
As part of this assignment you are required to evaluate contribution to the assignment of all the group members by using peer evaluation SparkPlus software at The evaluation includes self-evaluation and peer evaluation, you are also required to justify your evaluation by writing comments why you gave a group member a certain mark. Student can see the overall score given to them by other group members, but cannot see the comments or scores given by each individual group member, e.g. evaluation is anonymous. The SparkPlus evaluation is a requirement of the assignment, students who do not do the peer evaluation will not get mark for the assignment. Students who were evaluated as contributing less will have the mark reduced.
For example:
If total assignment mark for the group is 12 out of 15, Student who contributed well will get 12×1=12 marks.
Student who did not contribute well will get 12x 0.8 =9.6 marks, where 0.8 is the peer evaluation score. Marking Criteria

Criteria Description Marks
Introduction and conclusion Brief introduction to the report
Provide a brief report indicating each student contribution to the project must appear in the first page of the report.
Sum up your report (how have you learnt, the most important aspects….) 10
Question 1-9 • The marking point are mapped with the questions. Regarding each question, full marks are awarded for the correct solution, description or explanation and the answer responds clearly the question asked. The use of supporting evidence, illustration and calculation is correctly relevant to the answers. The answers show all the steps solved for the question.
Demonstration The demonstration will be run during the laboratory in Week 10 and 11.
Student should demonstrate their simulation in LTSpice and Matlab for the question.
Software/program must include in the moodle 20
Reference Style and presentation IEEE reference style
Nice presentation of the report including format report, spelling and grammar. 10
Poor writing • Inadequate structure, careless presentation, hard to read or the report is too short – 40
Plagiarism Type of plagiarism
Copy from other student
Copy from internet source/textbook
Copy from other sources -220
Total Marks 220
SPARKPLUS RPF Factor 0 – 1
Final Marks = Total Marks x SPARKPLUS RPF Factor


Question Marking Scale
HD 80%+ D 70%-79% C
60%-69% P
50%-59% MN
Introduction and conclusion Concise and specific to the exercise Topics are relevant and soundly presented. Generally relevant and sufficiently presented. Some relevance and briefly presented. Not relevant to the assignment topic.

Question 1
Question 9 All answers are present with excellent solution. Logic is clear and easy to follow with strong arguments, explanation and calculation. Proper writing. Professionally presented. Answers present with very good solution. Consistency logical and convincing. Properly written, with some minor deficiencies. Answers present with good solution. Mostly consistent and convincing. Mostly good, but some unclear or presentation problems. Most answers present. Adequate correct and conviction. Acceptable presentation. Lacks answers or unclear to question. Poor structure and careless presentation.
Demonstrati on Student demonstrates full knowledge and provides interesting presentation sequence of information that one can follow easily. Student demonstrates good knowledge and provides logical sequence of information which one can follow. Student demonstrates average knowledge and provides average logical sequence of presentation. Student demonstrates average knowledge and provides no logical sequence of information with few mistakes. Student demonstrates poor knowledge and provides no logical sequence of information with lots of mistakes.
Style and presentation Clear styles with excellent source of references. Clear referencing style. Generally good referencing style. Unclear referencing style. Lacks consistency with many errors.
Report is presented professionally. Report is written properly with some minor mistakes. Report is mostly good, but some structure or presentation problems. Report is presented acceptably. Report presented carelessly with
poor structure.

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