University of West London
BEng (Hons) Electrical and Electronic Engineering
Module: Electrical Theory 1 (TC40052E) Coursework
This assignment carries 50% of the marks available for this module.
Submission deadline: Word-processed copy on Blackboard 6.00 pm Friday 22th May 2020
All work should be the student’s own work. Plagiarism and collusion are serious assessment offences and will be reported.
Section A DC Measurements
Learning Outcomes:
• Use basic circuit laws to calculate currents and voltages in DC electrical circuit networks.
• Verify results using measurements.
Guidance to students
This technical report should be properly formatted and should include contents page, introduction, results, discussions and conclusions. All figures and tables are to be numbered and provided with a respective legend. All theoretical workings, simulation results, tables and plots obtained from practical work should also be included. It is recommended that equations be written using for example, Microsoft Equation Editor. Do not include screen dumps in your report. The report is to be written using a suitable text editor such as Microsoft Word and submission is done electronically using Turnitin on Blackboard.
Technical reports are written in the third person. Do not use ‘I’, ‘we’ etc. All figures and tables should be numbered and labelled and referenced from the text.
Care should be taken when using the equipment to ensure safe working practices. You will need to check that the range of the multimeter is working as incorrect operation or connection in the circuit by you or a previous user can blow the internal fuse. Measurements should be made as accurately as possible. The marking scheme is provided at the end of this document.
Task 1: Use of multimeter to carry out circuit measurements in a DC network
Equipment:
DC Power Supply
Digital Multimeter
Breadboard
Resistors: 100Ω, 220Ω, 390Ω, 470Ω, 560Ω.
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Procedure
1. Identify resistors R1 to R5 supplied and measure each of their resistances on the multimeter.
2. Record your results in Table 1.
Table 1: Resistor values
Resistor
Nominal Resistor Value (Ω)
Measured Resistor Value (Ω)
R1
100
R2
220
R3
390
R4
470
R5
560
Figure 1: Measurement of resistance in resistor network.
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3. Using a breadboard, connect the circuit as shown in Figure 1.
4. Measure the total resistance of the network and record your result in Table 2 indicating
clearly the units of measurement.
5. Connect the circuit as shown in Figure 2.
6. Set up the power supply, VS, to the value specified by your tutor and checking the reading
on the multimeter. Record this voltage value.
Figure 2: Measurement of voltage and current in resistor network
7. Measure the total circuit current, IT and record the result clearly indicating the units of measurement.
8. Measure the voltage across each resistor and record the results in table 2, indicating clearly the units of measurement.
Task 2: Use DC theory to calculate current, voltage and resistance in DC Network.
Using the resistor values measured for R1 to R5 in Figure 2 calculate:
i. The total resistance of the circuit
ii. The total circuit current, IT
iii. The current in each resistor
iv. The voltage across each resistor
You need to show all of your working on a separate sheet. Record the results in Table 2. Compare the results obtained for measured and calculated.
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Table 2: Voltage, Current and Resistance values
Circuit Measurement
Measured Value
Calculated Value
Circuit Resistance
DC supply Voltage
Circuit Current
Voltage across R1
Voltage across R2
Voltage across R3
Voltage across R4
Voltage across R5
Current in R1
Current in R2
Current in R3
Current in R4
Current in R5
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Learning Outcomes:
Section B
The Superposition Theorem
• Apply the superposition theorem to linear circuits with more than one voltage source.
• Verify results by simulation.
Task 1 – Theoretical analysis
Figure 3
You are required to use the superposition theorem to compute the currents flowing through each resistor in Figure 3 and the voltages across each of them. Your steps should consist of finding the total resistance when considering each voltage source, the current contribution from each source for each resistor and their corresponding voltage drop. You can tabulate your results for each step if you wish.
Task 2 – Simulation
Construct the circuit in Figure 3 using a suitable circuit simulation package such as OrCAD and compute the current through each resistor and the voltage across each of them.
Task 3 – Analysis and conclusion
Compare the results from Tasks 1-2 and provide an appropriate conclusion.
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Section C Voltage Divider Design Task
You are provided with a 12 V supply and a set of E12 series resistors. Your task is to design a voltage divider which produces a 5 V supply across a load resistor, which varies between 40 kΩ → 400 kΩ.
The detailed specifications for the circuit is given below:
• The 5 V supply should be accurate to within ± 7.5% across the range
• A maximum of 3 resistors should be used
• Assume that the nominal values of the resistors are the actual one, i.e., ignore their tolerances.
• The current drawn by the divider should not exceed 1.5 mA. Your solution should include:
i. A circuit diagram of your design with component values
ii. Calculations of the voltages supplied to the range of load resistors, showing that the
minimum and maximum values are within the specified range
iii. Calculation of the maximum current supplied by the source
iv. Simulation of your circuit, with a DC sweep of the load resistors for the above range
v. Determine the Thévenin’s equivalent circuit of your voltage divider and use it to find the current that would flow in a 30 kΩ resistor
vi. An analysis of the work undertaken.
Assessment criteria:
• The degree to which the work uses standard conventions, is clearly presented and requires little or no editing from the marker of the work.
• Clearly shows that the problem has been understood and makes process of solving the problem clear by annotating the process that is being undertaken.
• Coherence, clear expressions and arguments, referencing, including an introduction and a conclusion.
A detailed marking scheme is provided in pages 7 and 8.
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