National Institute of Technology
We seek to create and develop Vibrant, Skilled, Competent and Work-prepared Entrepreneurial Technicians, Technologists and
Professionals for the industry and the national economic vitality.
School of Applied Engineering and ICT
Diploma in Electrical and Electronic
Engineering
(Level 6)
TOTAL
MARKS: 100
Main
Assignment
2EEE305: Electrical and Electronic Principles
Due date: 03 June 2021
Total marks: 100
Assessor: Ms. Kaarina Ngula
Moderator: Mr. Ndahepele
Instructions to Students
1. Answers must be typed (font size 12, Arial)
2. An assignment submitted after the deadline will NOT be marked
3. Plagiarism is a serious offence and can disqualify your assignment
4. Assignments and Projects are subject to be checked through TURNITIN for plagiarism
Verification.
1
Scenario:
You are presented with the following tasks by the company where you train. The
electric network company must carry out these tasks within a specified time limit
and most importantly with the highest of standards and proficiency. To prove to
the company that you are the right person to work for it you must carry out these
tasks with utmost efficiency and professionalism and within the specified time limit.
All the tasks involve solving AC and DC networks using the theory and practical
experiences you acquired in your modules. All the tasks must be clearly and
professionally presented.
Task 1
1. For the circuit shown below: Circuit 1
Choose 5 different value resistors from the following table for resistors R1 – R5
Choose a value of supply voltage from the table for V1
Resistor values for R1 –
R5
10 Ω
Voltage values for V1
3 volts
22 Ω
5 volts
33 Ω
6 volts
47 Ω
9 volts
100 Ω
10 volts
220 Ω
12 volts
330 Ω
15 volts
470 Ω
24 volts
1k Ω
2
Calculate:
a) The total circuit resistance Rt
b) The total circuit current It
c) The current flowing through R3
d) The voltage dropped across R2
e) The power dissipated by R1
f) Confirm the results of your calculation using the laboratory simulator
(Proteus)
[2]
[2]
[2]
[2]
[2]
[10]
Task 2
2. Use Proteus to run the simulation:
a) Draw and label a diagram of a general purpose diode connected in forward
bias and reverse bias mode.
[5]
b) Measure the forward and reverse characteristics of the 1N4001 diode using
Proteus, record your results in a suitable table and use them to plot a graph.
[5]
c) Measure the forward and reverse characteristics of a zener diode of your
choice using test and measuring equipment, record your results in a
suitable table and use them to plot a graph.
[5]
d) Compare the two graphs showing the conduction characteristics of both
diodes, consult the data sheets and evaluate your findings in terms of
forward and reverse voltages, power dissipation and maximum operating
current.
[5]
3
Task 3
3. Construct the circuit shown below in Proteus:
a) Connect the circuit to the power supply as shown
[1]
b) Calculate the time constant of the circuit
[4]
c) Set up an oscilloscope to measure the voltage across the capacitor using
suitable time and amplitude settings
[2]
d) Switch on the circuit and measure the rise in capacitor voltage for 5 time
constants. Save your results as a screen dump
[4]
e) Switch off the circuit and measure the decay in capacitor voltage for 5
time constants. Save your results as a screen dump
[3]
f) Show how the rise in capacitor voltage is related to v =Vmax (1 – e –t/cr) [3]
g) Show how the decay in current is related to i = Imaxe-t/cr
[3]
Task 4
4. For the circuit shown below:
Use the same table as for Q1 in order to choose component values.
4
a) From the attached table choose different values for R1 – R3
b) From the attached table choose different voltages for V1 –V2
c) Use Kirchoff’s laws to determine the current flowing through R1, R2 and
R3
[5]
d) Determine the power dissipation in R1
[5]
Use Proteus to confirm the results of your calculations and attach to the
Assignment as a screen dump.
[10]
Task 5
5. A 4 pole generator has a lap-wound armature with 50 slots with 16 conductors
per slot. The useful flux per pole is 30 mWb. Determine the speed at which
the machine must be driven to generate an e.m.f. of 240 V.
[5]
Task 6
6. A d.c. shunt-wound generator running at constant speed generates a voltage of
150 V at a certain value of field current. Determine the change in the generated
voltage when the field current is reduced by 20%, assuming the flux
is proportional to the field current.
[5]
5
Task 7
7. The armature of a d.c. machine has a resistance of 0.25 Ω and is connected to
a 300 V supply. Calculate the e.m.f. generated when it is running:
a) as a generator giving 100 A
[5]
b) as a motor taking 80 A
[5]
Total Marks: 100
6