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Resistance in a wire - investigate whether or not the length of a piece of a wire affects the resistance

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Introduction

Physics Coursework

Aim

To investigate whether or not the length of a piece of a wire affects the resistance

Background Information

Resistance is a measure of how difficult it is for a current to flow in a circuit. It is measured in Ohms.

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The higher the resistance the lower the current.

 Ohm’s Law is all about resistance. It is: I = V/R.

So to work out resistance the equation is R = V/I.

Preliminary

I plan to investigate how the resistance of a 32 swag nichrome wire is affected when i change the length of the wire that is used in the experiment.

Length of Wire (cm)

Current (A)

Voltage (V)

 Calculation

Resistance

Wire at 10cm

1.44

3.27

3.21/1.33

2.27

Wire at 20cm

0.9

3.32

3.32/0.9

3.68

Wire at 30cm

0.61

3.34

3.34/0.61

5.48

When I did the preliminary I did not use a variable resistor. In order to get accurate results I must keep my current the same at every length. To do this I can use a variable resistor. By adjusting the settings on a resistor

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Middle

Cello-tape                                                x1

Lead – To create the circuit with and to keep it complete in order to carry out the experiment.

Crocodile Clips – To attach the leads to the nichrome wire and allow the circuit to be complete.

Variable Resistor – To control the current and keep it the same at every length in order to make my experiment a fair test.

Nichrome 32 swag wire – This is the wire I am testing the resistance of.

Metre Ruler – This is used to keep the nichrome straight and to measure the length of the wire.

Power Pack – This is my power supply. Without it the circuit would not work.

Ammeter – This is used to measure my current.

Voltmeter – This is used to measure my voltage.

Calculator – I will use this to do the calculations and work out my resistance using Ohm’s Law.

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Conclusion

I can tell that my results are fairly reliable because, on my graph, my line of best fit falls in between all but one of the error bars. However I cannot be totally sure of my results as two of my results had to be discounted. This was because they were drastically different to the other results in that sample. These outliers could have been caused by a slight error in measuring out the wire or by an error when setting the variable resistor to keep the current constant. This could have caused a fluctuating current. These problems can be resolved by checking everything before I take any readings.        

One thing I could have to done to improve the reliability of my results was to do more repeats. If I had more readings then my averages would become more reliable. However I feel that with the amount of repeats that I took I can be, overall, fairly confident in my results.

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