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Factors that affect the resistance of awire.

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Miranda Lewis Physics Coursework Nov. 2001

Factors that affect the resistance of a wire.

Preliminary Work.

At the beginning of the year we carried out two investigations entitled “To investigate the relationship between P.D and current in a metal resistor,” and “To investigate whether the resistance of a lightbulb filament changes as it heats up.” We carried out the experiment and then produced separate graphs for the investigations.

From the results I obtained from the 1st experiment I plotted a graph (which was a straight line) and then calculated the resistance.

Resistance/Gradient = difference on y axis

                        difference on x axis

Resistance = 8                 = 15Ω


From 2nd experiment I also plotted a graph, for this one it was a curve showing that the resistance was changing continuously due to the wire getting hotter as the current was on for a long time.

There are many factors that affect the resistance of a wire. They include;-

  • Length of the wire
  • Thickness or area of cross section of wire
  • Type of material of wire
  • Temperature of wire

I am going to investigate what affect the length of the wire has on its resistance. I have chosen to investigate length as it would be too hard to investigate different types of material

...read more.



To keep this experiment as accurate as possible we need to make sure that the length of wire is measured precisely, from the same point every time i.e. at the end of the ruler. We need to ensure that the wire is straight when we measure and when the experiment is carried out. If it is not, short circuits may occur and bends in the wire may also effect the resistance. The reading from the voltmeter and the ammeter must be taken as quickly as possible. As soon as the power is switched on the wire will get hotter and I want to test the wire when the heat is effecting it the least, which is obviously at the beginning.

...read more.


Errors did not occur when setting the current it was kept constant at 6V and recording the result readings on the ammeter and voltmeter was fairly simple and therefore accurate. I feel that taking more results would improve the accuracy because it would enable us to have more values to calculate a resistance. Errors could have been encountered when measuring the wire as it was not always pulled straight, the wire was not always kept at the same beginning point whilst measuring so each measurement could have been a few centimetres out.

It is also possible to extend the experiment of the factors affecting the resistance of a wire. We could use different materials of the wire to see how they behave because in this particular experiment I always used nichrome. One could also investigate different thickness’ of the wire i.e. increasing the cross sectional area as in the experiment already performed we used the same wire therefore the same cross sectional area.  I would predict that an increase in the cross sectional area would also lead to an increase in resistance, due to the same reason length has on resistance i.e. the electrons that make up the current would have to travel through more fixed particles in the cross sectional area of the wire therefore causing more collisions and thus a higher resistance.

...read more.

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