Question

Question 7 a) A The Circuit below was used to collect measurements of the current through and Potential difference across an unknown piece of material labelled as the 'Eureka Wire'. The table below shows the results of this experiment. Use the table below to plot a graph of Potential difference against current, with current on the X-axis. Use the Graph paper on the next page (8 marks) b) Use your graph to estimate the resistance of the 'eureka wire' between 0.1 A and 0.6A. Are there any anomalies in these results? State which value of current you may consider repeating a measurement for (3 marks) c) Explain the shape of the graph after 0.7A of current flows through the wire. What has happened to the resistance and why? (3 marks) d) Eureka wire is now replaced by a thermistor. Sketch below the graph of potential difference against current that may be expected for a Thermistor (4 marks) Total 18 marks Space to answer Question 7 here Current/A Potential Difference/ 0.1 1.0 0.2 2.0 0.3 2.6 0.4 4.0 0.5 4.9 0.6 6.0 0.7 7.5 0.8 9.0 LV power supply Eureka wire

Answer 1

7. a. The graph for the given data is as follows:

Resistance 10.00 9.00 8.00 7.00 6.00 y = 5.4762x2 +6.3333x + 0.3786 R2= 0.9977 Potential Difference/V 5.00 4.00 3.00 2.00 1.00 0.00 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 Current/A

The graph shows the relation between Potential Difference and Current to be a polynomial of order 2 and a curve fitting of 99.77%.

7.b. There are very few deviations from the graph but none enough to be considered an anomaly.

7.c. The graph after the current of 0.7 A shows almost a linear growth suggesting resistance becomes constant.