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Resistance of a Wire

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Introduction

Resistance of a Wire

By Rebecca Wisdell

11RG

Aim

I will be investigating how the resistance of the wire is affected by the length of the wire.  

Equipment

The apparatus needed for this experiment are:

  • Metre ruler – I decided to use a metre stick instead of a 30cm ruler because I needed to measure a metre of wire so it is precise to use a metre stick and will decrease my error.
  • Nickel chrome – After experimenting with other materials I decided to use nickel chrome because it gave us more accurate results.
  • Power pack – I decided to use a low voltage of 6V so that over heating was minimilised but also would give me good results.
  • Ammeter- In my experiment I used a digital ammeter instead of an analogue ammeter because the digital ammeter gave me more precise readings.
  • Voltmeter- I also used a digital voltmeter instead of an analogue voltmeter because the digital gave me more precise readings.
  • Wires x6
  • Crocodile clips x2

Preliminary Work  

Before I carried out the real test I did some preliminary work to find a suitable and most appropriate variable to change.

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Middle

Method

Firstly set up the apparatus like shown below: image00.png

  1. Once apparatus are all connected correctly set the power pack voltage to 6V
  2. Turn on the digital voltmeter and ammeter
  3. Cut a 100cms of nickel chrome wire , tighten the wire as much as you can to ensure your test accurate
  4. Sello-tape the wire to the ruler leaving a cm gap, so that you can attach the crocodile clips to the 0cm and 100cm mark.
  5. Turn on the power pack, you will notice that the readings on the voltmeter and ammeter are changing frequently, this is because the power pack may be unstable. Wait for the readings on the voltmeter and ammeter to settle a bit and then take the readings.
  6. Turn off the power pack and move the crocodile clip down to the 90cm mark, leaving the other crocodile clip on the 0 cm mark.
  7. Repeat step 5.    
  8. Each time move the crocodile clip down 10cms until you reach the 20cm mark.
  9. The entire investigation is repeated 2 times for accuracy.

Fair Test

To ensure that the experiment is a fair test all of the variables (except for the length of the wire) must be kept the same by not changing the method and equipment.

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Conclusion

The solution to this is to measure the lengths more carefully and ensure that the wire is pulled tight against the metre rule. During my experiment I noticed that the power pack was slightly unstable so this could have also affected my results but only by a little bit. However, as this error was the same for every test it wouldn’t have made any difference to the overall result. For a particular result, one or more of the connections could have been faulty, causing extra resistance at the connections. A solution to this would be to, before each experiment, connect the connections together without the wire in place and measure the resistance then. If it is higher than it should be then the connections could be cleaned. The results of the experiment could be improved by repeating it more times to help get rid of any anomalies and a better overall result. To get a better range of results I could have tested more lengths of wire.

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This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism section.

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