EAT119 – Electrical & Electronic Principles

EAT119 – Electrical & Electronic Principles Laboratory 1 – DC Circuits Introduction This activity allows you to experimentally test and confirm your understanding of DC circuit theory including: - a) component recognition, b) resistors in series (Kirchhoff’s Voltage Law), c) resistors in parallel (Kirchhoff’s Current Law), d) Maximum Power Transfer theorem, e) circuit simulation using Proteus. To complete this exercise, you will require the following items, which are available on request from the technician who is based in room DG201: - ? 9 volt PP3 battery and battery clip (or a variable DC power supply) ? Single strand wire and wire stripper ? Pack of 4 resistors1 ? Multimeter ? Prototype board (breadboard) 1. Ten different resistor sets are available, and you must request the correct set, based on the last digit of your student number, prior to the ‘/’. For example, if your number is 123456789/1 then you should request resistor set ‘9’. These items must be returned in good condition after use. FAILURE TO USE THE CORRECT SET OF RESISTORS WILL RESULT IN A MARK OF ZERO! Task 1 – Resistor Colour Codes (10 marks) Your resistor pack contains 4 resistors, consisting of three unique colour codes, but with two resistors identically marked. a) Use the resistor colour code to identify the stated value and tolerance band of each unique resistor code (2 marks). b) Measure the actual resistance of each resistor by using a multimeter (2 marks). c) Create a table showing the colours of each band, nominal value, tolerance and measured value of each of your resistors (2 marks). d) Comment on whether your measured resistance values are within the stated tolerance, the accuracy of your results, and any potential sources of error (4 marks). Task 2 – Resistors in Series (Kirchhoff’s Voltage Law – 10 marks) Use a prototype board to construct a series circuit with your 4 resistors, as shown. a) Measure the actual EMF produced by the battery and the potential difference across each resistor (V1, V2, V3 and V4) (2 marks). b) Use your results from part a) to prove Kirchhoff’s Voltage Law (2 marks). c) Calculate the total resistance of the circuit and then use Ohm’s law to predict the current which would be expected to flow through the circuit (2 marks). d) Connect an ammeter in series with the battery and measure the current flowing (2 marks). e) Comment on your results and whether these agree with theory, and explain any differences (2 marks). Task 3 – Resistors in Parallel (Kirchhoff’s Current Law – 10 marks) Use a prototype board to construct a parallel circuit with your 3 unique resistors2 , as shown. 2. Do not use the duplicate resistor for Task 3. a) Measure the actual EMF produced by the battery (2 marks). b) Connect your multimeter as an ammeter (i.e. in series) and measure the total current from the battery ( ), and also the current flowing through each resistor ( , , and ) (2 marks). c) Use your results from b) to confirm Kirchhoff’s current law (2 marks). d) Calculate an equivalent single resistance which could replace R1–R3. Use this value to calculate the expected total current, and compare this with the total current measured in b) (2 marks). e) Comment on your results (2 marks). Task 4 – Maximum Power Transfer Theorem (10 marks) Begin by constructing the above circuit, setting the source and load resistors to be your two identical resistors. a) Measure the battery voltage, the voltage across RS and RL and calculate the power dissipated in each resistor (2 marks). b) Replace the load resistor with each of your other three resistors, repeating the calculations from part a) in each case (2 marks). c) Comment on which load resistor allows the maximum power to be transferred, and the efficiency of power transfer (2 marks). d) Is ‘maximum power transfer’ the same as ‘maximum efficiency’? Explain your answer (4 marks). Task 5 – Proteus simulation (10 marks) Pick ONE of your circuits from Tasks 2-4. a) Create a Proteus simulation3 of your chosen circuit, and include a screenshot in your report as evidence (3 marks). b) Use your simulation to repeat the chosen activity, recording all simulation results and repeating all calculations (3 marks). c) Discuss your findings, commenting on whether they agreed with theory, and with your experimental results, accounting for any differences (4 marks). 3. Proteus simulation software is available in areas E + F of the David Goldman Informatics Centre. A Proteus user guide for DC Circuits is available on SunSpace. Task 6 – Written Report (30 marks) You must produce an individual word processed report which gives evidence that you have completed all required activities. This must be submitted online through SunSpace by 11.59 PM Friday 5th February 2016. Marks will be awarded for: - a) Appropriate report structure, use of language and style (10 marks) b) Effective use of IT (10 marks) c) Linking of experimental results with theory, supported by appropriate references (10 marks) Task 7 – Electrical Health and Safety (20 marks) As part of the practical you have been asked to give an overview of the current UK standards and approved codes of practice that should be observed when working in the electrical laboratory. The activities a student would be expected to carry out in the laboratory include using testing and measuring equipment that is supplied by the mains power. Your overview should also include a “Code of Practice” which gives brief instructions to users of the lab on how to comply with the standards. This section of your report should be no longer than 500 words. Marking Scheme Task 1 Resistor Colour Codes /10 Comments Task 2 Resistors in Series (Kirchhoff’s Voltage Law) /10 Comments Task 3 Resistors in Parallel (Kirchhoff’s Current Law) /10 Comments Task 4 Maximum Power Transfer Theorem /10 Comments Task 5 Proteus Simulation /10 Comments Task 6 Report Structure /10 Use of IT /10 Links to Theory, supported by References /10 Comments Task 7 Health and Safety /20 Comments Total: ______ / 100 Appendix A – Circuit Construction Hints and Tips Example Wiring - Series Resistor Prototype Board Circuit Example Wiring – Parallel Resistor Prototype Board Circuit Measuring resistance The resistor must be disconnected from the circuit before attempting to measure resistance. Measuring Voltage and Current Voltage may be measured by connecting the meter in parallel with the chosen component. Voltage is measured while the circuit is ‘live’. (The voltmeter has a very high internal resistance so should not affect the circuit.) Current is measured by connecting an ammeter in series with the component whose current is to be measured. Current is measured while the circuit is live. (Caution: The ammeter has a very low internal resistance and will be damaged if it is connected in parallel, unlike a voltmeter.)