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# To investigate how the resistance of a wire changes with length.

Extracts from this document...

Introduction

Jamal Muse 10H

Science Investigation- Resistance Of Wire

Aim- To investigate how the resistance of a wire changes with length.

The dependant variable is the resistance of the wire.

The Key Variables are:
1. Wire length
2. Material
3. Wire diameter
4. Temperature
5. Wire Density

Wire length:
If the length of the wire is increased, then the resistance will increase. This is due to the electrons having a longer distance to travel and so more collisions will occur. Due to this, the length increase should be directly proportional to the increase in resistance.

Material:
The type of material will effect the number of free electrons, which are able to flow through the wire. The number of electrons depends on the amount of electrons in the outer shell of the atoms, so if there are more atoms then there are more electrons available. If the material has a high number of atoms, there will be a higher number of electrons. This will cause a lower resistance because of an increase in number of electrons.

Wire diameter:
If the wire diameter is increased the resistance will decrease. This is due to the increase in space for the electrons to travel through. Because of this increased space between the atoms, there should be fewer collisions.

Middle

What is resistance?

Electricity is conducted through a conductor, in this case wire, by means of free electrons. The number of free electrons depends on the material and more free electrons means a better conductor, i.e. it has less resistance. For example, gold has more free electrons than iron and, as a result, it is a better conductor. The free electrons are given energy and as a result move and collide with neighbouring free electrons. This happens across the length of the wire and thus electricity is conducted. Resistance is the result of energy loss as heat. It involves collisions between the free electrons and the fixed particles of the metal, other free electrons and impurities. These collisions convert some of the energy that the free electrons are carrying into heat.

### Ohm’s Law

It is also relevant to know of Ohm’s Law, which states that the current through a metallic conductor (e.g. wire) at a constant temperature is proportional to the potential difference (voltage). Therefore V ¸ I is constant. This means that the resistance of a metallic conductor is constant providing that the temperature also remains constant. Furthermore, the resistance of a metal increases as its temperature increases. This is

Conclusion

Evaluation

I think that overall my experiment went quite well and that the results were fairly accurate, but in order to make them even more accurate I could have measured the current more times before taking an average. This may also reduce the anomalies on my graph. The other, smaller anomalies could have been caused by bends in the wire, making the length longer than it should have been. These things may have caused errors in my results, but I think that generally my results are accurate enough to support my conclusion.

From my results table and graph I can see that my results that I collected are very reliable. I know this because my results table does not show any individual anomalous results this means that I did not have to leave any results out of my averages because they were anomalous. Also on the graph I can see that none of the averages plotted are anomalous because all the averages lie along the same straight line.

To extend this experiment I could use different thicknesses of wire to prove the conclusions I have drawn are correct. I could also try using wires made from different metals to see if they would make a difference to the resistance.

I think that the equipment I used was the most suitable for the task and that my method was fairly easy to follow.

Overall, I think my experiment went very well, my prediction was correct.

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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