Prediction and Hypothesis:
There are many things that I can change in this experiment, they are:
Temperature
Thickness
Length
Material
SWG
Cross-sectional area
Wire diameter
I have decided that I am going to need to have a continuous variable, so I have chosen to change the length of the wire. I predict that the longer the wire is, the more resistance it will have. I therefore predict that Length and Resistance will be proportional to each other, as the length increases so will the resistance.
I predict this as the longer the wire, the further the current has to travel, so it will have more resistance then if it were a shorter wire. It will have more pushing against the flow of electrons, and so it will have more resistance. Longer wire means more obstruction, so it means more resistance.
If we say the circuit represents water flowing through some pipes. The power pack is the driving force pushing the water around, and the wire is the obstruction, which will slow the water down, and cause resistance. If the obstruction (wire) is longer, then it will slow the water down a lot. The more of this wire there is, the more resistance there will be. This is why I predict that the length of the wire will be proportional to the resistance, as one goes up, so will the other.
Results:
Observations:
I observed that the wire got hot when I was constantly using it. This could have affected the resistance a bit, as when the wire is hot the electrons in it are already moving very fast as they have a lot of energy. This would have made the resistance more then it should be, as the atoms are moving fast.
Conclusion:
From my results I can tell that the length is proportional to resistance, they go up by approximately the same intervals each time. This is what I predicted, as you increase the length, the resistance will also go up. They are proportional as, if you increase the length, e.g. 5cm to 10cm, the resistance goes up proportionally, 0.36 to 0.49 Ohms. This is because the current has more material to go through, and so it is harder to get through. This is the resistance getting bigger.
This is because the longer the wire, the further the current has to travel, so it will have more resistance then if it were a shorter wire. It will have more pushing against the flow of electrons, and so it will have more resistance. Longer wire means more obstruction, so it means more resistance.
From my results I have come up with the equation Y/X=Gradient. From this all you have to do is find out the gradient of part of the graph, and then if you want to know how much resistance a 2m wire would have, you just put in the numbers and rearrange the formula to give you the answer.
Extension:
If I were to take this experiment further, I would calculate the Length of Nichrome wire, the same as above, that I need in order to make a resistor of 10 ohms in size.
To do this I would first calculate the gradient of my graph. I have found two spots at which the measurement are pretty definite, (2.5, 0.2) and (21.5, 1.1). To find the gradient I divide the resistance by the length, which would be 0.9 by 19.0, and the answer would be 0.05. This is how steep the graph is.
Y/X=Gradient
I know the gradient is 0.05, Y is the Resistance, which in this case has to be 10 Ohms, and X is the length required to make this 10 Ohm resistor. So:
10/X=0.05
X=10/0.05
X=200cm or 2m
I would need 2m of the Nichrome wire, 24SWG 0.56mm, to make a 10 Ohm resistor.
Evaluation:
I think that my experiment did not work too badly, although there were some things that I could improve on. The wire that I used was not very straight, which would have affected the length when I measured it, this would have affected my results. For next time I need to make sure that the wire is straight, so that I can get more accurate results.
Heat was given off from the wire, which I noted in my observations, this would have affected the resistance a bit. Next time I can get rid of this by having a lower voltage pushing the current around the circuit, such as 1V, instead of 2V, and maybe wait until the wire is cool before I test the next length. This should stop the resistance being altered to something higher then it should be.
Overall my experiment went generally well. I ended up with a straight-line graph, although it was not exactly through the origin, like it should have been in theory. I was able to repeat my results to make them more accurate. I have no points that are that far out of place; they are all fairly close together in the straight line, so my experiment was successful.
