Does the length of a wire affect the resistance? -- A* - page 3
Keywords: Physics length of wire resistance
By georgie1 on 31/12/2009
Level: GCSE Key Stage 4 (Years 10-11)
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and affect my results, but will also provide a wide range of results.
Following this, I then checked that a wire of a diameter of 0.29mm would be appropriate for my final investigation, by ensuring I get significantly different resistances from two different lengths of wire. I used lengths of 1m and 0.2m and collected these results:
Length of wire/m Potential Difference/volts Current/amps Resistance/ohms Ω
1.00 0.18 3.18 0.06
0.20 0.32 3.96 0.08
I could see that the two results provided considerably different results and therefore am confident that this is the most appropriate diameter of wire to use in my final investigation. Following this experiment, I was also aware that I should only switch the power supply on for the shortest time possible, to ensure that the wire is not heated and therefore adding an extra factor to the resistance of the wire. This means that the only variable changing the resistance of the wire is the length.
Final Investigation
This is how I plan to set up my investigation.
Method:
1) Set up the apparatus in the way illustrated above.
2) Turn on power supply and decrease current to as low as possible.
3) Take readings from both the voltmeter and ammeter, and record.
4) Shorten the wire by 10cm each time and repeat steps 1-3.
5) Repeat steps 1-4 three times.
6) Calculate the resistance by using the formula previously given.
7) Work out an average result for each length of wire and use these results to plot onto a graph and draw conclusions.
Collecting my results
First Results
Length/m V Potential Difference/volts I Current/amps Resistance(V/I)/ohms Ω
0.20 0.27 2.92 0.093
0.30 0.32 2.68 0.119
0.40 0.41 2.48 0.165
0.50 0.47 2.39 0.197
0.60 0.44 2.14 0.206
0.70 0.49 2.11 0.232
0.80 0.55 1.98 0.278
0.90 0.58 1.97 0.294
1.00 0.62 1.82 0.341
Second Results
Length/m V Potential Difference/volts I Current/amps Resistance(V/I)/ohms Ω
0.20 0.26 2.61 0.100
0.30 0.31 2.46 0.126
0.40 0.40 2.31 0.173
0.50 0.43 2.19 0.196
0.60 0.42 2.09 0.201
0.70 Anomalous result 0.55 1.99
Replacement result 0.53 2.13 0.266
0.80 0.62 2.09 0.297
0.90 0.67 2.01 0.333
1.00 0.68 1.96 0.347
Third Results
Length/m V Potential Difference/volts I Current/amps Resistance(V/I)/ohms Ω
0.20 0.34 4.46 0.076
0.30 0.46 4.14 0.111
0.40 0.53 3.89 0.136
0.50 0.63 3.60 0.175
0.60 0.69 3.42 0.202
0.70 0.79 3.10 0.255
0.80 0.81 2.98 0.272
0.90 0.86 2.76 0.312
1.00 0.89 2.75 0.324
Average Results (these will be the results that I plot onto my graph and draw conclusions from because they are the most reliable).
Length/m V Potential Difference/volts I Current/amps Resistance(V/I)/ohms Ω
0.20 0.29 3.33 0.087
0.30 0.36 3.09 0.117
0.40 0.45 2.89 0.156
0.50 0.51 2.73 0.187
0.60 0.52 2.55 0.204
0.70 0.60 2.40 0.250
0.80 0.66 2.35 0.281
0.90 0.70 2.25 0.311
1.00 0.73 2.18 0.335
As you can see from my results, and the graph that I have created, there is a clear line of best fit that shows a constant increase in resistance. Generally, the line of best fit falls within the error bars, showing that I have recorded my results accurately and that I have kept the investigation fair throughout. The gradient of the line of best fit represents a positive correlation, showing that one factor causes the other to change. In this case, it shows that as the length of the wire increases, the resistance increases. This is because the outer electrons which are flowing through the wire will use more energy to pass through a longer length of wire. More energy is used because
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