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Whether the length of resistance wire affects its resistance, and if so how

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Introduction

Ollie Fleming 10G

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Introduction

Resistance wire has various uses in and around the house, including resistors, heating/lighting elements and in fuse boxes. It is made in different types and thicknesses.  The resistance of a wirecan be calculated using ohm’s law – V/A = R, (voltage divided by amps equals the resistance of the wire.) The resistance of a wire varies depending on its length, type and thickness.

Aim

The aim of this investigation is to find out whether the length of resistance wire affects its resistance, and if so how.

Apparatus

The following is needed for the practical experiment:

  • A power pack
  • Ammeter
  • Voltmeter
  • Crocodile clips
  • Connecting wires
  • A metre rule
  • Various lengths of wire to test

Preliminary Experiment

A preliminary experiment was carried out to determine the variant in the length of wire, the power pack voltage to be used and also to find out any other changes that could be made in our final experiment.  

Some of the possible factors to investigate were:

The length of the wire - The type of wire - The thickness of wire

We took some rough results and observed different lengths and types of wire at different voltages.  

We concluded firstly that voltages over 6 volts and short wire lengths (under 25cm)

...read more.

Middle

Try to make sure all the following are taken into account when carrying out the experiment to make it as fair as possible:
  • Make sure the wire is the exact length.
  • Make sure meters are reset before use.
  • Take and record results as accurately as possible (use mirrors on the back of meter scales).
  • Use the same type of wire each time.

Null Hypothesis (HO)

The change in length of wire will have no effect on the calculated resistance of the wire, or the resistance will decrease as the length of wire increases.

Hypothesis (HI)

The calculated resistance of the wire will increase significantly as the length of the wire increases.

Prediction

I think the resistance of the wire will increase steadily as the length of the wire increases, causing a strong positive correlation.

...read more.

Conclusion

Evaluation

The method I chose was not the best for accurate results and so was chosen for the following: -

  • Quick and easy to set up, and take apart each lesson.
  • Quick and easy to take results and measurements.
  • Not to involve any complex equipment.
  • Safe and hassle free.

I think the data I collected was in general accurate but does appear to have a fault between 30-50cm. This is reflected in the results – the graph shows a positive correlation, with only the sharp decline of what could be a fault in my result taking, a fault in the wire or meters. The experiment was carried out to the best of my ability. I thought my range was maybe not wide enough but for the time and conditions I had it was not bad. These few points are more likely to be real but could be the result of a poor method, mistake or a failure in the equipment.

Some changes in the method may have to be changed to ensure a faultless experiment. For example I could have been quite a bit more accurate with the length of wire. It would be interesting to investigate further some of the flaws I think may have occurred, for example: - the affect of heat on the wire’s resistance.

...read more.

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