PREN 1000 Study & IT Skills

PEME 1000 Electrical CircuitsAssessed Exercise Laboratory ObjectivesThe objective of assessed exercise is to give you the opportunity to demonstrate your competence in a range of areas covered in the lecture and practical sessions in this module specifically by: Designing an experimental method to investigate electrical circuit behaviour; Collecting experimental data and quantifying measured information; Presenting data in a standard format using MS Excel; Analysing these results and using further functionality in MS Excel to fit a model to the data; Producing an experimental report, in a recognised standard format, using MS Word.Format of your ReportYour experimental report must be word processed using MS Word and incorporate other MS Office components, e.g. MS Excel and MS Powerpoint, as necessary.Your report must conform to the standard layout and grammatical conventions for an experimental report, as follows. Title and Author Abstract a brief (100-150 words) summary of what was done, why it was done, what was found and what was concluded. Background an introduction including context, background science, aims and objectives. Experimental Method a description of what was done, including figures (which must have captions and be cited in the text), with sufficient detail to enable another researcher to assess and reproduce the experiment. Past tense, passive voice must be used since it is an impersonal report it is not a recipe! Results the data generated by the experiment presented in tables and/or basic graphs with description but not interpretation or analysis (this belongs in the next section). Tables and graphs to have captions (e.g. Table 1, Figure 1) and to be cited in the text. All dimensioned data must have units clearly indicated in tables and graphs. SI units only. Discussion interpretation of the data presented in the previous section. This would normally include comparison with existing data and/or mathematical models, explanation of anomalies in the data, assessment of significance of the results. Additional graphs may well be presented, e.g. to illustrate the fitting of a model to the data. As before, all figures and tables must be captioned and cited, and it is conventional to number any equations so that they can be referenced in the text. Conclusions a brief summary of what was carried out, what was found, what interpretation was drawn from this and what is its significance. Bullet points or lists can often be very effective. References a list of references consulted in drawing up the report. As with previous exercises, these must be cited in the text of the report in a manner which clearly indicated which material is taken/ adapted from which source. Harvard or Numeric referencing style is required.SupportDemonstrators will be present in the laboratory to assist you with planning and carrying out your experiment. If you are unclear about the interpretation of your data or how to write your report, please consult them for advice before leaving the laboratory.

HelpTry the following link for some further guidance on report writing: http://www.leeds.ac.uk/lskills/TLTP3/WS/repintro.htmlThe ExperimentBackgroundElectrical current in a simple circuit depends on the value of the applied voltage and the combined resistance of components in the path between the positive and negative points of the voltage source. The value of the current is determined by:

(1)

where I is the current, V the applied voltage and R the value of the resistance.

The power consumed by an electrical component is determined by the current that flows throw it and voltage that is applied. In the most basic case this power is dissipated as heat causing a temperature rise in the component. In other cases the applied power can be transformed into light, sound or movement. The power P is calculated with the expression:

(2)

An electric current flowing trough a wire generates a magnetic field. Winding the wire into spool has an additive effect on the magnetic field of the individual loops. If the magnetic effect is strong enough it can be used to move other objects with magnetic properties. Applications of this effect are found in relays and electric motors.

Experiment 1. Plot graph of Voltage vs. current and confirm resistor value.Connect voltage and current meter to Resistor 1 for the experiment. Apply voltage source to circuit. Use at least 5 different voltage values ranging from 1 V to 12 V. Record voltage and current values from meters and plot a graph. What is the actual resistor value from the measurements? Repeat the experiment connecting the two resistors in series, then two resistors in parallel.

Figure 1. Resistor and voltage source connection for measurement of voltage and current.

Experiment 2. Plot temperature vs. voltageAttach the temperature sensor to the resistor. Apply around 5 different voltages to one resistor and this time record the temperature. Plot a graph of the temperature versus voltage allowing time for the temperature to stabilise.

Experiment 3. Relay magnetically controlled switch.Connect the switch to the coil of the relay and the 12 V voltage source. Be careful not to apply more than 12V! Observe what happens when the switch is pressed. Explain how the circuit works and what other applications a magnetically controlled switch could have.

Figure 2. Diagram for connection of experiment with relay and LEDs

Experiment 4. Electric motor FanConnect the fan motor to the 12 V power supply through the switch. The fan moves because of the magnetic field generated by the electric current. Explain how the circular movement is created as opposed to the linear action of the relay in the previous experiment.

Experiment 5. Magnetism Set the power supply to a maximum current of 1 A. a) Connect a wire to the supply and the switch. Position the wire over a magnetic compass or next to it and press the switch. Observe the needle of the compass and explain why this happens.b) Make a coil by turning the wire several times around an object like a pen. Repeat the experiment and observe the compass. Is there a difference? If so why?