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Investigate how changing the length of a piece of wire affects its resistance.

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Introduction

Chris Caulfield – 11K125th October 2003

Wire Resistance Investigation

Aim:        To investigate how changing the length of a piece of wire affects its resistance.

Prediction:        I already know that a short piece of wire has fewer atoms for the electrons to flow through, using the domino effect.  This causes there to be less resistance in the circuit.    This means that as the length of the wire gets longer the resistance in the circuit increases.

I predict that the longer the wire the higher the resistance.  This is because the electrons go slower because they meet more atoms.  Therefore the lower the current the higher the resistance.  

Equipment:        This is the apparatus I will use for my experiment:

  • Two batteries
  • Connecting wires
  • Volt meter
  • Ammeter
  • Heat proof mat
  • Wire
  • Crocodile clips

Diagram:

Plan:        We will be testing 5 different lengths of wire (20 cm, 30 cm, 40 cm, 50 cm and 60 cm) to find how this affects the resistance.  To do this we will do the following:

  1. Set up all equipment (as seen in above diagram – an ammeter, a volt meter,

2 batteries and cut a length of wire, at least 60 cm long)

...read more.

Middle

30cm

20cm

Test One

Test Two

Test Three

Average

Resistance

(Ω)

Length of wire

Current

(I)

Potential difference

 (V)

Current

(I)

Potential difference

(V)

Current

(I)

Potential difference

(V)

Current

(I)

Potential difference

(V)

60cm

1

2.7

1

2.7

1

2.7

1

2.7

2.7

20cm

2.3

2.3

2.3

2.8

2.3

2.5

2.3

2.54

1.1

My prediction appears to be correct as I stated above, that the longer the length of wire the higher the resistance.  The results in my results table also support my prediction and I will not therefore be changing my original plan as there is no need to do so.  I have followed the plan exactly as I have written it down.

Results:        This is the results table I am going to use for my final results so far.

...read more.

Conclusion

Evaluation:

My prediction was correct.  I did find that the shortest length of wire had the least resistance and that the longest piece had the highest reading.  My original prediction therefore appears to be accurate.  Also my preliminary work backed up my results from my experiment and has given me reliable results.   To make sure that the longest wire does have the greater resistance I would like to test longer pieces of wire to see whether the gradual increase that I found in my graph would continue.

To improve the experiment I could use more pieces of wire, e.g. up to 1 metre of wire to see whether it behaves as the other wire lengths did.  Also I could increase the wire lengths by 5 cm, not 10 cm as in this experiment.  I could test their resistance and get more accurate results of how resistance behaves in various wire lengths.  This will provide more results to base a firmer conclusion on.

...read more.

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