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How length affects resistance in a wire

Extracts from this document...

Introduction

How length affects resistance in a wire

Introduction

For this investigation I must get a set of results which shows how a length of a wire will affect the resistance of it. I will be testing how when I change the length of a wire the resistance should change as well. I will be using this formula to show how I will calculate the resistance:        

Voltage/Current=Resistance

This was discovered by Georg Ohm in 1827 and was such an important discovery that they named the unit for resistances as Ohms. For this investigation I will need to understand the theory of current and resistance. Electricity is the flow of electrons around a wire. As these electrons flow round the wire they collide with the metal atoms, these collisions makes the atoms vibrate more which makes them hotter. Resistance is a material that tries to stop the flow of electricity through it. To perform this experiment I will need to investigate the variables that I will need to keep constant and the variable that I will be changing.

image07.png

Variables

Materials- The material that we use to measure resistance would have to stay the same if we were to measure how the length of a wire will affect the resistance of it. This is because the material of the wire will change the resistance through the wire because some materials will be better conductors than other materials. Even if the wire is the same length the material can affect the resistant through it. This variable will be controlled by me as I will only use one material to measure the resistance at all the different lengths. I will make sure that I choose a material that I will keep the same through all different lengths.

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Middle

0.3/0.4

30

0.67

40

0.78

50

0.7/0.8

60

0.92

As you can see from the results I got extremely random results and at some lengths I wasn’t even getting results as it was always changing. After looking at this I decided that we had to change something to our method. So for are next test I decided to lower the current through the circuit by using the rheostat. I thought this would help because I imagined that the voltage would not move around because there is less current flowing through the circuit. I decided to drop the current to 0.04 Amps, and this worked well as I got a good set of results that were easy to perform. Here are the results:

Length(cm)

Voltage( Volts)

Resistance(Ohms)

10

0.07

1.75

20

0.15

3.75

30

0.23

5.75

40

0.31

7.75

50

0.38

9.5

60

0.46

11.5

As you can see from the results I have a lot better set of results that match my earlier prediction. I now have results to show that my method will be good to further these results, to allow them to get a more reliable conclusion. I used preliminary to test all the apparatus that I would be using and to do test runs to make sure that my method was reliable.

Method

Equipment

.Power supply

.Electrical wires to connect circuit (6 needed)

.Ammeter

.Voltmeter

.Rheostat

.Wire Board

.Ruler

1) Collect all the equipment- All the equipment that we decided to use we had tested in preliminary to see if they would work well. We had to evaluate each piece of equipment to make sure that it was write for our experiment as you cannot have equipment that may make the results you get wrong or unreliable.

2) Plug the power supply into electricity socket and attach one end of a wire into the power supply and another wire into the other available hole in the power supply-

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Conclusion

Another reason why I feel that my results are extremely reliable is that we can see a pattern in them. This shows that there is a link and is showing consistency in the experiment. It also shows that they aren’t random results that are all over the place. If we had more time I think it would be interesting to see if we could test more lengths and the pattern continued. This would make my results even stronger and even more reliable. So overall I feel that my results are extremely reliable because I have taken three results that are similar, I have scientific knowledge to back them up and you cans see a pattern in the results that show consistency.

I feel that if we had more time it would be a good idea to get more results. I think it would be good to get lengths all the way up to 100cm. It would be interesting to see if the line on the curve continued upwards and that the pattern continued.

Conclusion

From our results we can see that as the length of wire increases the resistance gets bigger. This is my final conclusion that I made after I evaluated how my investigation went, I feel like this is a fair conclusion after we have graphs that prove it and we have performed repeated tests to check if they are correct. I feel the investigation went well and we have finished with some positive results.

...read more.

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