Case Study 1

References Provides full details of sources of information Author. (YEAR). Title. Place of Publishing. Publisher. Lave, J. (1988) Cognition in Practice, Cambridge: Cambridge University Press. Minimum of 3 different sources of information – EG: Web page, Newspaper, TV program, Textbook, Scientific Journal, Magazine... 2

Physics Behind the Case Study Paragraph describing the case study in general and it’s applications. Paragraph on the Physics behind the case study. 3

Scientific Language + Spelling + Grammar + Subheadings + Picture Use correct scientific terminology fluently Spelling Grammatical mistakes kept to a minimum Use subheading to structure you planning and analysis Provide a graph, picture or diagram that helps to explain a point you have talked about 4

Contexts and Implications Write a paragraph on the social/environmental/historical impacts of your case study. How has it affected societies/cultures? Benefits AND risks of the technology 5

How does the Case Study relate to the Experiment? Relate the case study to the experiment you will be doing A couple of sentences 6

Planning 7

List Materials + List Safety Issues List all materials required in dot points Safety? What happens to the wire if you increase the voltage too much? Gets hot. 8

Appropriate Equipment Correct Measuring Technique Cross-Sectional Area of Wire (m2) – Mircometer Length of Wire (m) – Ruler Resistance (Ohms) - Multimeter 9

Number of measurements to be taken and why 1.Micrometer – How many measurements of the diameter of the wire? 2.Multimeter - What is the Scale you used in your measurement? Explain why this is the most accurate range to use. 10 Scale of instrument and why

Independent and Dependent Variable Independent Variable – The thing that you change in the experiment Dependent Variable – The thing that you measure in the experiment 11

Controlled Variables What other variables can affect your experiment? 1.Temperature 2.Thickness of Wire And how can you control these? 12

Repeated Reading You should take 3 resistance readings for each length Think about your results table. 13

Discuss Why you are collecting the Data and what you intend to do with it Read Page of Revision Guide Making a graph... Using this graph to calculate the gradient.. What will the gradient tell you.. Can you calculate Resistivity from the Gradient... (see A7) 14

Sources of Uncertainty Equipment – Ruler ( m) – Mircometer ( ) – Multimeter ( ) 15

Diagram + Organised Planning Draw a labelled diagram of equipment Plan is well organised Step-by-step procedure 16

Multimeter 1.Insert the probes into the correct connections - this is required because there may be a number of different connections that can be used. 2.Set switch to the correct measurement type (Ohms). When selecting the range, ensure that the maximum range is above that anticipated. The range on can then be reduced as necessary. By selecting a range that is too high, it prevents the meter being overloaded. 3.If possible enable all the leading digits to not read zero, and in this way the greatest number of significant digits can be read. 17

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Analysis 19

Significant Figures Ruler = 3 significant figures. Eg: 0.100m Multimeter = Micrometer = Significant Figures In a calculation involving multiplication/division, the number of significant digits in an answer should equal the least number of significant digits in any one of the numbers being multiplied/divided. Thus in evaluating AxB, where A = (2 significant digits) and B = 4.73 m (3 significant digits), the answer should have 2 significant digits. 20

Table Use correct units – Metres – Ohms Obtain appropriate number of measurements At least 6 Obtain measurements over an appropriate range. Eg: over a whole metre 21

Graph Axis labelled correctly Correct units Points plotted accurately and neatly Line of best fit Do not join the dots Graph should be a straight line 22

Sensible scales Your increments on the y and x-axis should be equal. – Eg: 0, 5, 10, 15, , 10, 20, 30, Graph 23

Comment on Trend Comment on trend / pattern obtained Graph should be Directly Proportional Two quantities are said to be Directly Proportional if they vary in such a way that one of the quantities is a constant multiple of the other, or equivalently if they have a constant ratio (eg: they have a constant gradient). 24

Calculating the Gradient Determines the constant (Gradient) The gradient will allow you to say what you said in A5, but be able to use numbers to explain it in more detail You should be able to make a statement such as “For every 1m increase in length, the resistance increases ‘insert gradient’ Ohms”. 25

Related Physics Principles From the gradient calculation, you should now be able to calculate the Resistivity Gradient = Resistivity / Cross Sectional Area Resistivity = Gradient x Cross Sectional Area Compare this with the actual resistivity of the material. 26

Sources of Error Instrumental Limitations Uncertainties are inherent in any measuring instrument. A ruler, even if as well-made as is technologically possible, has calibrations of finite width; Analogue devices such as thermometers or burettes often require the observer to interpolate between graduations on the scale. Some people will be better at this than others. Human Error Really it hinges on the experimenter doing the experiment truly to the best of his ability, but being let down by inexperience. Such errors lessen with practice. Errors Due To External Influences Such errors may come from draughts on the electronic balance, for example or maybe from impurity in the chemicals used. Such things are unlikely to be significant in a carefully-designed and executed experiment, but are often discussed by students, again because they are fairly obvious things. Not All Measurements Have Well-Defined Values Properties such as the diameter of a planet, for example, although quoted in tables of data, is a mean value, do not have well- defined values. The same is true for the thickness of a piece of paper or the diameter of a wire. These measurements will vary somewhat at different places. It is important to realise what sort of data you are dealing with. 27

Experiment Improvements Modifications – Was temperature properly controlled? – Could more accurate equipment be used? 28

Calculating Uncertainties Ruler – The minimum measurement on a 1 meter ruler is 0.001m (1mm). Therefore the uncertainty in this measurements is half of this = m (half a mm). Vernier Callipers / Micrometer – The minimum measurement Multimeter - The minimum measurement on a multimeter is The uncertainty in the cross sectional area will need to be doubled because the radius is squared. 29

Conclusion Final Conclusion State the resistivity of the material with the percentage uncertainty you calculated. Compare your answer to the correct value (Teacher will have on the front desk) 30