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My aim is to observe whether the length of a nichrome wire affects its resistance.

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Introduction

Resistance of a Wire Investigation

AIM

My aim is to observe whether the length of a nichrome wire affects its resistance.

PREDICTION

Based on my scientific knowledge, I feel that the shorter the length of wire, the less resistance there will be, and vice-versa – the longer the length of wire then the more resistance there will be. I have based this prediction on the knowledge that when the wire increase in length, the more current will be required, therefore decreasing the current and increasing the resistance. Another reason for my prediction is that when electrons are in the circuit, they are forever losing energy. While going through a longer wire and longer circuit then the electrons will lose energy and more will be sent, creating yet more resistance.  I hope my graph for the experiment to look like this:

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I also carried out a run-through of the test in a preliminary investigation and I found that the resistance does increase with the length of wire.

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Middle

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CHANGES FROM TRIAL EXPERIMENT

While trialling the experiment I felt that the following changes needed to be made:

  • Measure at 10regular intervals instead of the original 5 – it will ensure that I will get a better average.
  • Use sellotape to stick wire to ruler – stop wire become twisted and keep it straight on the ruler.
  • For the shorter lengths of wire, the power pack must only be on for a matter of seconds, due to the lack of wire needing to get through, the particles will build up and melt the wire.

METHOD

  • Measure a piece of 0.25mm nichrome wire to 100cm
  • Connect all components together using crocodile clips
  • Attach the wire to the ruler, using Sellotape.
  • Switch the power unit onto 6 volts and onto a direct current, I only want the current to be flowing one way and not alternating.
  • Measure 10cm on the ruler, turn the P.S.U. on and take the reading on the ammeter and voltmeter. I will do the same for 20cm, 30cm, 40cm etc. Before repeating the process again, twice for all 10 measurements.
  • Use the formula, RESISTANCE = VOLTAGE
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Conclusion

If I did the investigation again, I wouldn’t be able to use a resistor, which would defeat the point of the experiment. I’m not sure how I’d tackle this problem. I could also have used a digital voltmeter instead of an analogue one because the analogue one would be a lot less accurate than a digital one. I feel the analogue one is less accurate because I would have had to read the meter manually with my whereas a digital one would have given a much more detailed reading. I could also change a variable, which would see the problem from a different perspective; I could look at the thickness of the wire or the voltage at which the power pack is set. This would give me more data to work with, on top of the set of results in this experiment.  

 In conclusion, I feel this experiment was quite successful although more tests mean a more accurate result.

...read more.

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