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To investigate how the length of a wire affects the current flowing through it.

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Introduction

PHYSICS COURSEWORK

Aim- To investigate how the length of a wire affects the current flowing through it.

For me to investigate this I must first use my scientific knowledge to understand exactly how and why the length of a wire should affect the current flowing through it. From this I will then be able to devise a suitable test.

Scientific Knowledge

Electric current- is the flow of electrons round a circuit. The current is produced from moving electrons, which are free to move around the circuit. They flow opposite to conventional current which, means they travel from negative to positive. Current is measured in Amperes (A).

Electrons can only move from the negative terminal of a battery to the positive end if there is an electric path between them. Materials that allow electrons to move through them easily, to form an electric current, are called conductors. These are mainly metals such as copper, gold and silver and also carbon (non-metal). Materials that do not allow electrons to move through them easily are called insulators. The wire going to be used is a metal and so this is why a current will pass through.

Anything that slows the electrons down, by the atoms of the material resisting the flow, is a source of electrical resistance. All materials oppose current passing through them. It is this opposition that is the resistance.

Middle

2.73

The results of the amount of current proved to not show enough range between the results and so would not give an accurate and reliable answer, after analysis, to either prove or disprove the prediction. It was therefore evident that I would have to change the resistance of the variable resistor to create more resistance to hopefully give a better range to the current results. This would make the data easier to analysis.

The same test was repeated three times so that an average of the three tests could be calculated creating fairer and more reliable results that would, hopefully, give constant results.

Results of 3 tests

TEST 1

 Length (cm) Current (A) Voltage (V) 0 -0.92 0.04 5 -0.85 0.52 15 -0.71 1.48 25 -0.61 2.15 35 -0.54 2.64 45 -0.48 3.04 55 -0.44 3.35 65 -0.40 3.64 75 -0.37 3.87 85 -0.34 4.05 95 -0.32 4.21

TEST 2

 Length (cm) Current (A) Voltage (V) 0 -0.92 0.03 5 -0.85 0.55 15 -0.70 1.53 25 -0.61 2.23 35 -0.54 2.72 45 -0.49 3.10 55 -0.44 3.40 65 -0.40 3.68 75 -0.37 3.89 85 -0.34 4.06 95 -0.32 4.20

TEST 3

 Length (cm) Current (A) Voltage (V) 0 -.090 0.10 5 -0.85 0.52 15 -0.71 1.51 25 -0.61 2.14 35 -0.54 2.68 45 -0.48 3.07 55 -0.44 3.41 65 -0.41 3.67 75 -0.37 3.89 85 -0.35 4.15 95 -0.32 4.25

The current ranges were 0.6.

Conclusion

Evaluation

I feel that I have performed this investigation to my best capability and I believe that I have made a fair and valid conclusion.

However, there were some odd results shown in my graphs and tables, although all the currents has a range of 6 so the results were not too obscure which means I still believe that my results are valid. These were probably due human error on my behalf or matters beyond my control.

I believe that my experiment was suitable as it clearly showed a good conclusion, it was not hard to follow and formed a good basis for my investigation. Yet there are ways in which my experiment could be improved to overcome any errors that occurred such as; I could use a baby thermometer to check the heat of the wire to see if it was hot so that I could see where to end the experiment. I would end the experiment where heat was being produced, as at this time Ohm’s Law would mean that the experiment wasn’t working anymore and the results were becoming invalid. I could also repeat the experiment further so as to gain a mean from more results meaning fewer occurrences of errors in the findings. Also, if I was to use a higher resistance on the variable resistor it would mean less current and so less heat would be produced meaning more consistent and valid results

To expand on this investigation I could experiment with different lengths of wire, wires of different materials and different temperatures as we used room temperature

SALLY DWIAR

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