BTEC National Diploma in Engineering

Unit 6

Electrical and Electronic Principles

Unit Name and Number Student Assessor

Task book issue date Completion date (pass outcomes) Learner Signature

Outcomes included in this task bookTasks are ordered in accordance with the outcomes listed

Achieved? AssessorSignature

P1Use DC circuit theory to calculate current, voltage and resistance in DC Networks

P2Use a multimeter to carry out circuit measurements in a DC circuit

P3Compare the forward and reverse characteristics of two different semi conductor diode

P4Describe the function of different types of capacitors

P5Carry out and experiment to determine the relationship between voltage and current for a charging and discharging capacitor

P6Calculate the charge, voltage and energy values in a DC network for both three capacitors in series and three capacitors in parallel

P7Describe the characteristics of a magnetic field

P8Describe the relationship between flux density (B) and field strength (H)

P9Describe the principles and applications of electromagnetic induction

P10Use single phase AC circuit theory to determine the characteristics of a sinusoidal waveform

P11Use an oscilloscope to measure and determine the inputs and outputs of a single phase AC circuit

M1Use Kirchoff’s laws to determine the current in various parts of a network having four nodes and the power dissipated in a load resistor containing two voltages sourcesM2Evaluate capacitance, charge, voltage and energy in a network containing a series-parallel combination of three capacitors

D1Analyse the operation and the effects of varying component parameters of a power supply circuit that includes a transformer, diodes and capacitorsD2Evaluate the performance of a motor and a generator by reference to electronic theory

Learner Declaration

I confirm that the work submitted to complete the given tasks is my own. I have indicated where research and other resources have been used to confirm the conclusions reached within the submission and listed those resources in a bibliography

Sign and date for each task

P1 P2 P3 P4

P5 P6 P7 P8

P9 P10 P11 M1

M2 M3 D1 D2

Task 1 Covering P1

Before you submit your work to be marked for this task please check the following, if you omit any of the items listed in the table you may have to repeat the submission.

Check the following Tick to confirm you have fulfilled the requirements for this outcome

Have you properly introduced the task, explaining what you are trying to achieve?Are your calculations clearly laid out with answers double underlined?Have you put your name on the submitted work?

Have you produced drawings to back up your calculations? Especially drawings showing how the circuit is broken down to calculate resistance.Have you used a simulator to check your calculated results?

Have you provided screen dumps with this submission to prove the accuracy of your calculations?

Task 1 P1

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 Voltage values for V1

10 Ω 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

Calculate:

The total circuit resistance Rt

The total circuit current It

The current flowing through R3The voltage dropped across R2The power dissipated by R1Confirm the results of your calculation using the laboratory simulator (Multisim)

Care should be taken by each student to ensure that the combination of components and supply voltage are unique for each assessment.

Task 2 P2

Evidence requirements

Check the following Tick to confirm you have fulfilled the requirements for this outcome

Have you made sure you have the performance evidence statement signed?

Have you evaluated the differences between the calculated, measured and simulated results? What could cause the difference in the results for exampleHave you provided a plan of the circuit you made along with the correct test points to make the required measurements?

Once again have you properly introduced the task to your reader and informed them of what you are attempting to accomplish?

You are required to construct the circuit used for P1 above. You are to use test equipment to carry out the following measurements as listed in the table below. You need to have the witness statement.

Parameter Calculated values Measured values Simulated values

Total circuit resistance

Total circuit current

Current flowing through R3

Voltage dropped across R2

Power dissipated in R1

For this observation the learner:

Safely constructed a DC network comprising of 5 resistorsConnected the network to a DC source (5 volts)Correctly demonstrated the safe use of a multimeterUsed a multimeter to measure voltage, current and resistance in accordance with the set tasksWas able to contrast and compare the readings taken by a multimeter with calculated and simulated results

Signed Observer ……………………………….. Date …………………………….

Task 3 P3

Evidence requirements

Check the following Tick to confirm you have fulfilled the requirements for this outcome

Have you introduced the task to your reader?

Are your drawings neatly completed in pencil?

Are all of your drawings and graphs completed in pencil and neatly labeled or given headings where appropriate?

Have you provided a table for all of the results you measured both in the simulator and using the laboratory test equipment?

Have you properly read all of the tasks below to make sure you are providing all of the evidence required?

You are required to use test equipment to measure the forward and reverse characteristics of two semi-conductor diodes. In order to carry out this experiment you will need to read through the instructions on www.mindfyre.co.uk.

Tasks

Draw and label a diagram of a general purpose diode connected in forward bias and reverse bias modeMeasure the forward and reverse characteristics of the 1N4001 diode using Multisim, record your results in a suitable table and use them to plot a graph.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 graphCompare 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

Task 4 P4

Check the following Tick to confirm you have fulfilled the requirements for this outcome

Have you introduced the task to your reader?

Have you drawn and labeled a simple diagram explaining how a capacitor is constructed?

Have you given a typical application for each of the types of capacitor listed? For example electrolytic capacitors are used in power supplies because of their high capacitance and energy storage.Have you attempted to explain in your own words how a capacitor works?

Describe the function and type of capacitors

This is best completed using a table of values, consult www.mindfyre.co.uk for more information on this task

Tasks

Describe the following list of capacitors in terms of their construction, working voltages, dielectric, flux density, permittivity and energy storage:

ElectrolyticMicaPlasticPaperCeramicFixed and variable

Task 5 P5

Check the following Tick to confirm you have fulfilled the requirements for this outcome

Have you introduced the task to your reader?

Have you checked your measured results and your calculated results?Have you provided a photograph of the oscilloscope trace showing the capacitor charging and discharging?Have you evaluated this task?

Did you use the formula below to plot a basic graph of showing how the voltage changes across a charging capacitor?Did you use the formula below to show how the current decreases through a discharging capacitor

Construct the circuit shown below, if you need further guidance you can consult www.mindfyre.co.uk

Tasks

Connect the circuit to the power supply as shown Calculate the time constant of the circuitSet up an oscilloscope to measure the voltage across the capacitor using suitable time and amplitude settingsSwitch on the circuit and measure the rise in capacitor voltage for 5 time constants. Save your results as a screen dumpSwitch off the circuit and measure the decay in capacitor voltage for 5 time constants. Save your results as a screen dumpShow how the rise in capacitor voltage is related to v =Vmax (1 – e –t/cr)Show how the decay in current is related to i = Imaxe-t/cr

Task 6 P6 (Evidence requirements should be apparent by this stage)Calculate the charge, voltage, capacitor and energy values stored by each capacitor for the following networks. Check www.mindfyre.co.uk for further details and support.

Task 7 P7

Check the following Tick to confirm you have fulfilled the requirements for this outcome

Where you are asked to describe something, it should be your description in your own words. You can use other information sources to confirm your explanationIt’s fine to use information sources to define the properties of a magnetic field. However make sure you confirm your understanding in your own wordsHave you provided labeled sketches to back up your descriptions of the items listed below?

1) Draw the magnetic field associated with a permanent bar magnet and use the diagram to carry out the following tasks.

a. Give 5 general properties of a magnetic field.b. Define flux, flux density and magnetic field strengthc. Describe the effects of reluctance and hysteresis with respect to magnetic circuits.d. Define the term ferromagnetic and give three examples of a ferromagnetic materiale. Describe the process and advantages of magnetic screening

Task 8 P8

Check the following Tick to confirm you have fulfilled the requirements for this outcome

Have you provided two graphs? One for relative permeability and the other for flux density?Have you briefly explained what you deduce is happening to both materials as the magnetizing force is increased?Have you provided a table showing how you calculated the relative permeability of each material for the 5 given stages?

Plot the B/H curve on a suitable graph for the materials shown on the table from the given data and determine the relative permeability (µr) of the material for each stage. Given that µo = 4 x 10-7 H/m find the range of relative permeability for each material.

Use the data plotted on the graph to analyse and explain the relationship between the two given materials in terms of flux density (B) and magnetizing force (H)

Remember relative permeability µr = B/(H x µo)

Plot the graph that shows relative permeability against the magnetizing force

Describe what happens to a material as the magnetizing force is increased in terms of flux density and relative permeability

Magnetizing

Force (H) At/m

Mild steel

Flux density (B) Tesla’s

Cast Iron

Flux density (B)

Tesla’s

1000 0.7 0.3

2000 1.24 0.48

3000 1.45 0.6

4000 1.55 0.67

5000 1.6 0.72

Task 9 P9

Check the following Tick to confirm you have fulfilled the requirements for this outcome

Have you explained the laws using your own words?

Have you used sketches to show how the laws listed below operate, and are the provided sketches completed in pencil and neatly labeled?Have you included any of the simple transformer calculations which help to show how a transformer operates?In both the case of the 3 phase motor and the transformer, how does your description of how both machines operate relate to Faraday’s laws?

Use the following tasks to describe the principles and applications of electromagnetic induction.

a. Define Faraday’ laws in your own words using diagrams where appropriate.b. Define Lenz’s law in your own words using diagrams where appropriate.c. Draw a diagram of a simple AC generator and use Fleming’s right hand rule to demonstrate the

direction of the current in the rotating conductor when it is perpendicular to the North Pole.d. Explain the principle of operation of a simple transformere. Explain the principle operation of a 3 phase AC induction motor.

Task 10 P10 & P11

Check the following Tick to confirm you have fulfilled the requirements for this outcome

Have you included a sketch of a sine wave showing the major characteristics listed below e.g. periodic time?

Have you included a screen dump from Multisim to confirm your results showing circuit operation?

Have fully described and evaluated the experiment using calculations, sketches and photographs as appropriate to the tasks listed below?Have you suggested where and when this time of circuit might come in useful?

V1 is a function generator. You can use it to vary the frequency and amplitude of an ac voltage (for further details see the handbook). You can carry this experiment out either using a real oscilloscope, a virtual oscilloscope or by using Multisim (simulation software).

Remember the equation for a sine wave VInstantaneous = VSupply x sin(ωt +/- φ)

Set up the function generator to generate a sinusoidal waveform with an amplitude of 5 volts and a frequency of 1000 HzSet up an oscilloscope to measure the input signal(applied across both the resistor and capacitor) and the output signal applied just across the capacitor.Apply an input signal and measure the input and output using the oscilloscopeWith reference to your measurements define frequency, amplitude, periodic time, phase shift and the RMS value of the input and output waveforms.With reference to theory at what time (after t = 0) should the positive peak of the input signal occur?From your measurements, at what time does the first positive peak (after t = 0) of the output signal occurWith this information can you find the phase shift introduced by this circuit at 1000 Hz?

Task 11 M1

For the circuit shown below:

Use the same table as for P1 in order to choose component values.

Circuit 2

From the attached table choose different values for R1 – R3 From the attached table choose different voltages for V1 –V2Use Kirchoff’s laws to determine the current flowing through R1, R2 and R3Determine the power dissipation in R1

Use Multisim to confirm the results of your calculations and attach to the assignment as a screen dump.

Task 12 M2

Calculate the total capacitance, total charge, the voltage dropped across each capacitor and the total energy stored for the following network.

Task 13 D1

Tasks

Use an oscilloscope to measure the output voltage of this circuit at the point shownCompare the output voltage with the input voltage V1 (Screen dump)

From you initial measurements use the graphing function in Multisim to measure the ripple voltage of this circuitAdjust R1 until the ripple voltage of the circuit reads 200 mVFrom your results calculate the time constant for this circuitIf R1 = 100Ω what value of capacitance would be required to produce a ripple voltage of 200 mV?If the instantaneous current conducted by the capacitor on its charge phase is I = C x dv/dt, find the repetitive forward current conducted by the circuit on each charge phase (use the grapher function)Explain the importance of the Vrrm rating when designing power supply circuitsExplain why the voltage rating of the capacitor and the diodes should be at least twice the V rrm rating given

Task 14 D2

1) Draw and label the component parts of a basic DC machine.

2) Describe the action of a two segment commutator using appropriate diagrams.

3) Define:

a. Wave windingsb. Lap Windings

4) Briefly describe the operation of DC machines that are wound in:

a. Shuntb. Seriesc. Compound

5) Briefly describe armature reaction and show one way in which it can be overcome.

6) 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.

7) 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.

8) With reference to the basic construction of a d.c. machine state the principle difference between a d.c. generator and a d.c. motor.

9) 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 Ab. as a motor taking 80 A