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An investigation into the factors affecting the resistance of a wire.

Extracts from this document...

Introduction

Richard TandySeptember 2003

Year 11 Science Coursework

An investigation into the factors affecting the resistance of a wire

Introduction

        There are many factors that are known to affect the resistance of a wire. However, there are a few factors, which influence the resistance of a wire more than anything else. One factor, which determines the resistance of a wire, is the material in which the wire is made out of as the structure of metals influences resistance. The dimensions of the object and thetemperature in particular also affect the materials resistance, as the temperature increases the molecules gain energy, which results in more collisions and therefore more resistance. Moreover, the length of the wire will also govern the amount of resistance created. Density too (how thick or thin the wire is), has a large affect on the amount of resistance. For example, a large surface area has less resistance because a small area has tightly packed atoms, which in turn rebound many of the electrons. The factors that can be investigated in Physics are those known as quantitative results – these are results that have continuous data (such as length).

For this piece of coursework the factor that I will be investigating willbe how the length of a wire will affect the resistance in which acts upon it. I am not going to be investigating temperature, as it is too difficult to measure the temperature within a wire. Temperature affects the wire but as I am using the same piece of wire in the same classroom, I think that the wires temperature will be fairly equal throughout my experiment. Though it will not be 100% accurate.              

Background Knowledge

Voltage is the electrical force, or "pressure", that causes current to flow in a circuit. It is measured in VOLTS (V or E).

...read more.

Middle

3.85

     0.18            0.2            0.2

0.19

20.26

My table from my preliminary test will give me a rough and brief, scaled down guide to what my real results table should look like and provides a benchmark for my results. It also illustrates that resistance increased with length.I believe that my data is accurate because I have repeated the test three times in order to get a well-rounded average – this is what I will do in my real test.

Prediction
Aim: To investigate how the length affects the resistance of a wire.

I predict that as the length increases then the resistance will also increase in proportion to the length.                                                                                   This is due to the idea of the free moving electrons being resisted by the atoms in the wire. In a longer piece of wire, there would be more atoms for the electrons to collide with and so the resistance would be greater. The relationship between the wire length andthe resistance should be approximately proportional. This is because in a wire twice the length of another wire there would be double the amount of atoms causing the resistance. In theory, if the wire is doubled, then so will the resistance. If the length is twice as much, then there will be twice as much collisions, which would increase the resistance.

An example of this would be in a 20cm wire. The electrons would have to travel double to distance they would have to go through a 10cm wire. This would in turn double the amount of atoms that the electrons would collide with and then resistance would double.                                                                                        Furthermore, my preliminary test backs up my prediction because it illustrates that resistance increased with length.

I can further support my hypothesis because I know from my scientific knowledge and research that:

...read more.

Conclusion

Further experiments I could do which are related to the resistance in a wire, would be to see whether the following factors would make a difference in the resistance of a wire: (I have made a prediction for each factor from my own scientific knowledge on how I think the resistance would change in a wire for that particular factor):

" Wire width:

I think that if the wire width is increased the resistance will decrease. This is because of the increase in the space for the electrons to travel through. Due to this increased space between the atoms there should be less collisions.

" Temperature:

I think that if the wire is heated up the atoms in the wire will start to vibrate because of their increase in energy. This causes more collisions between the electrons and the atoms as the atoms are moving into the path of the electrons. This increase in collisions means that there will be an increase in resistance.

"Material:

I think that the type of material of the wire will affect the amount of free electrons, which are able to flow through that wire. This is because the number of electrons depends on the amount of electrons in the outer energy shell of the atoms, so if there are more or larger atoms then there must be more electrons available. If the material has a high number of atoms there will be high numbers of electrons causing a lower resistance because of the increase in the number of electrons. Also if the atoms in the material are closely packed then the electrons will have more frequent collisions and the resistance will increase.

Resources I used to help me with this coursework are:  

  • Science For GCSE – Graham Hill                                                

  • Physics In Action – Hal Leonard (US)

...read more.

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