LO1: Demonstrate solutions for engineering problems that meet a combination of societal, user, business and customer needs as appropriate.

Learning Outcomes

This assessment satisfies the following learning outcomes as specified in your Module Guide.

It is the students’ responsibility to familiarise themselves with the University’s policies on plagiarism and use of unfair means contained within the Student handbook.

How to submit

Please see Module Guide Section 12 “Guidelines for the Preparation and Submission of Assignments” which will give you details on how to submit your work electronically.  You are required to submit only electronic copies of your written assessments.

1. Introduction

This module aims to introduce you to basic electrical and electronic principles. You will explore the laws and theorems related to DC / AC electrical and electronic systems in the classroom, you will also have the opportunity to relate this to physical systems by undertaking practical experiments in the laboratory. Within these laboratory sessions, you will learn to use electrical measuring instruments, and be introduced to electrical machines such as transformers,generators and motors. Further topics include magnetism, inductance, electric fields, and capacitance. 

The purpose of this assignment is to provide hands-on sessions in the laboratory, examining simple DC/AC circuits, MATLAB simulation to show DC/AC circuit transients of RLC circuit. This will help in understanding the basic principles of the above topics and apply the knowledge to electrical systems.

1. Equipment Required

Oscilloscope, DC and AC power supplies, Breadboard, Multi-meter, AC Signal Generator, PC (with MATLAB/Simulink installed and access to Multisim).

3. Physical Outcomes

• Report

Students are asked to work as an individual and produce a report explaining what they have done in response to the given experiments, the Multisim and/or MATLAB simulation. This laboratory report should be no longer than 3000 words and contain the following contents:

The report should be word-processed, and formatted to look like a professional report, with alignments on both left and right side. Suitable font size should be used (12 for example) and font should be traditional like Arial, or Times New Roman, or others of your choice. But be consistent with the choice, do not mix them up in the middle of the report.  All diagrams should have a caption and a figure number. For example: Fig 10: Circuit Diagram of the integrator.  Always refer to this diagram in the text, and it forms a link from your discussion to the diagram.  This is good practice, and you will be penalized if you do not follow such rules.  Apart from diagrams, you should include experimental results – photos, or captured waveform from the digital oscilloscope.  Extra bonus marks will be awarded if you do the extra mile.  

All work will put through the Turn-it-in software to detect plagiarism. Just be warned.

4. Assessment Weighting:

This assessment will carry 60% of the total marks for this module.

The report should consist of the experiments results, calculations, the mathematical model, the simulation model & its responses and the solutions of four biweekly tutorial sheets.

The report will be graded based on the following criterias:-

1. Overall structure of the report (10%)
2. Five experiment reports (75%)
3. Mathematical model and MATLAB/SIMULINK Model (10%)
4. Evidence of the simulation responses and practical (or published) data (5%)

For the MATLAB/SIMULINK simulation the students are required to write the mathematical model of an RLC series circuit with DC/AC source first. Then build a simulation model using the MATLAB/SIMULINK software package. Finally analyse the time responses with the applied source, current in the circuit as well as voltage drop across each element of the circuit.

• Part A: 
• Objective: Use your theoretical knowledge of series-parallel circuits to calculate the values and record them in a table. Then build the circuit and measure the values.

• Procedure:

• Part B:
• Objectives: To calculate the equivalent total resistance of a circuit and compare calculated values with measured values.

• Procedure:

Using the same circuit from Part A:

• Part A:  Thevenin’s Theorem

• Objective:

To measure the Thevenin’s voltage and Thevenin’s resistance of a circuit.

To find out whether Thevenin’s theorem lets us correctly predict currents and voltages.

• Procedure

Table B: Thevenin Equivalent of Circuit 1

• This theorem says that our original Circuit 1 is equivalent to the simplified circuit shown below as Circuit 2.

• What does it mean to say that the original circuit and this simplified circuit are equivalent? It means that if we connect any additional components to Circuit 1, and connect the same additional components to Circuit 2, the resulting voltages and currents in those added components will be the same in the two circuits. In other words, the added components will have no way of "knowing" whether they are connected to the original Circuit 1 or to the simpler Circuit 2.
• For instance, suppose we just connect a single resistor to points a and b in the two circuits.
• By connecting a 470 Ω resistor across points a and b, we`ll end up with Circuit 3 and 4 as shown below.

• Measure voltage (V4) and current (I4) and record in Table C below.

Table C: V₄ and I₄ in Circuit 3

By connecting a 470 Ω resistor across points a and b in Circuit 2, we`ll end up with Circuit 4, shown below. Building Circuit 4 will be a bit trickier. Why?

Because you probably will not find a resistor in the cabinet whose resistance is equal to the value of RTH that you need. So how do you build Circuit 4?

By using a potentiometer that is carefully adjusted so that its resistance is equal to the desired value of R_TH.

Locate a potentiometer whose total resistance is greater than the R_TH that you need. Then, while using a DMM to monitor the resistance between the middle terminal and one end terminal of the potentiometer, adjust the potentiometer until you get the desired resistance.

Now you can build Circuit 4, using the potentiometer as your R_TH.   

1. After building Circuit 4, measure V₄ and I₄, and record their values in Table D.

Table D: V₄ and I₄ in Circuit 4

11. Your measured values of V4 and I4 for the two circuits (3 and 4) should be very similar to each other.

• Part B:  Superposition Principle

• Objective:

              - To build and make measurements on circuits with more than one voltage source.

              - To find out whether the superposition principle correctly predicts currents and voltages in such circuits.

              - To find out whether Kirchhoff`s laws apply to such circuits.

• Procedure

1. Use the superposition principle to calculate the values in the circuit below. Enter these values in table E.
2. Then build the circuit and measure the quantities.
3. Record your measured values, along with percentage errors. 

Table E

• Objective: To create Alternating Current (AC) frequencies we use the Function Generator, it can generate AC frequencies from zero to 10MHz with amplitudes up to 30volts pp (peak to peak)                                                                                                               

We use the Digital Oscilloscope to observe these signals.

The Oscilloscope cannot change the parameters of the signal, but we can use the functions on the Oscilloscope to analyse, observe and take readings of the signal. 

• Procedure

• Switch ON the Function Generator and Switch ON the Digital Oscilloscope.
• Connect using the BNC cables provided from the 50Ω OUTPUT terminal on the Function Generator TO the CH1(yellow) terminal on the Digital Oscilloscope
• Press the ‘AUTOSET’ button on the oscilloscope and observe the waveform from the Function Generator
• By pressing the FUNCTION button on the Function Generator you can observe various waveforms, Sine, Triangular, Square and Digital.

• Part A

1. Set up a sine waveform with a frequency (F) of 75Hz

2.  Using the VOLTS/DIV control knob on the Oscilloscope set the display at   1volt/div observe the sinewave and adjust the amplitude control on the Function Generator to give a display showing 6v peak to peak (Vpp).

1. Using the timescale adjustment, measure the time T of one complete cycle (360º)
2. Using the equation       ,          

Find and confirm the frequency of 75Hz.

Part B

Setup and observe a sine wave on the oscilloscope with a 110Hz frequency and with a Vpp shown in the table below.

Complete the table below:

Peak Voltage (Vp) = 0.5(Vpp)

RMS values = 0.707(Vp)

Part C

• To set up a Digital pulse 

1. Set the signal generator to 50Hz sine wave with a Vp-p of 6v.
2. Locate and enable the digital function, to switch to a digital waveform.
3. Locate and enable the ‘Offset’ control.
4. Using the ‘Offset’ adjust, set up a digital pulse of 5ms ON time and 15ms OFF time on the oscilloscope.
5. What is the TOTAL time period for the pulse.
6. For the timings above we have a 25% duty cycle

1. Set up a digital pulse with a duty cycle of 50%

Part D

 In a circuit which dissipates electrical energy, the ratio of voltage (V) to current (I) is termed the circuit resistance (R).

In a circuit which stores energy, the ratio of voltage (V) to current (I) is termed the circuit reactance (X).

Capacitors and inductors store electrical energy and both have reactance.

• Part A – Capacitance (C)

Capacitive Reactance (Xc) is inversely proportional to frequency f, and inversely proportional to capacitance C.

For a pure capacitance in a circuit with a sinusoidal input waveform, the current leads the voltage by 90°. 

• Procedure:

1. Construct the circuit below on the breadboard.
2. Use a multimeters to measure current Ic- (mA)
3. Use a multimeter to measure Voltage Vc- (V)
4. Set up the Oscillator to provide an AC Sinewave at 500Hz and a Voltage (amplitude) of 1V rms on the Voltage multimeter at Vc
5. Find the value of Ic for differing frequencies and complete the table below. 

For each set of measured readings, find the capacitive reactance Xc and

record these values in the table below.

Where;  Vc= RMS voltage

and where;  Ic=RMS Current

Using measured values -Plot the Capacitive Reactance/Frequency characteristic graph. 

• Part B – Inductance (L)

Since inductors store electrical energy, the ratio of applied voltage to current flowing through an inductor is the inductive reactance.

Inductive Reactance s(XL) is proportional to frequency f and proportional to inductance L.

                               XL = 2πfL

For a pure inductance in a circuit with sinusoidal input waveform, the current lags behind the voltage by 90°.

• Procedure:

1. Construct the circuit below on the breadboard.
2. Use a multimeter to measure current IL- (mA)
3. Use a multimeter to measure Voltage VL- (V)
4. Set up the Oscillator to provide an AC Sinewave at 500Hz and a Voltage (amplitude) of 1V rms on the Voltage multimeter at V_L
5. Find the value of I_L for differing frequencies and complete the table below. 

For each set of readings, calculate the value of Inductive reactance XL and record these values in the table below.

Where, V_L= RMS voltage

and where; I_L=RMS Current

Using measured values- Plot the Inductive Reactance/Frequency characteristic graph.