The readings were taken when the voltage was:
3 v
And the length of wire was: -
0.0 – 200.0 cm every 10.0 cm
Prediction
I think that as the length of the wire increases so will the resistance of it. I also believe that the rate at which the resistance of the wire increases will be directly proportional to the length.
Theory
As a result of the structure of all conductive metals, the outer electrons are able to move about freely even in a solid. When there is a potential difference across a conductive material all of the free electrons arrange themselves in lines moving towards the positive charge. This forms an electrical current. Resistance is encountered when the charged particles that make up the current collide with other fixed particles in the material. As the resistance of a material increases so must the force required to drive the same amount of current.
As the length of the wire is increased the number of collisions the current carrying charged particles make with fixed particles also increases and therefore the value for the resistance of the wire becomes higher.
It is much harder for the electrons to travel through this:-
than this:-
Preliminary Work
2 Meters - 1 Volt
1 Meter – 2 Volts
2 Meters – 3 Volts
From the preliminary work I know that I can safely work with a voltage up to 3v so I have decided to use 2 meters of wire and 3 v because it would give me a good line of best fit and the wire would not get too hot.
Results
Analysis
From the graph on the previous page I can see that the resistance of the wire is directly proportional to the length of the wire. I know this because the Line of Best Fit is a straight line, apart form the two anomalies, showing that if the length of the wire is increased then the resistance of the wire will also increase. It also shows that as the length doubles so does the resistance:-
e.g. 10.0 cm – 0.85 Ω
20.0 cm – 1.78 Ω
Conclusion
In my prediction I said that as the length of wire increases, the resistance will also increase in proportion to the length. From my graph I have shown that my prediction was correct, as the Line of Best Fit is a straight line apart from the anomalies, proving that the resistance of the wire is proportional to the length of the wire. The length of the wire affects the resistance of the wire because the number of atoms in the wire increases or decreases as the length of the wire increases or decreases in proportion. The resistance of a wire depends on the number of collisions the electrons have with the atoms of the material , so if there is a larger number of atoms there will be a larger number of collisions which will increase the resistance of the wire. If a length of a wire contains a certain number of atoms when that length is increased the number of atoms will also increase.
It is much harder for the electrons to travel through this:-
than this:
In this diagram the wire is half the length of the wire below and so has half the number of atoms, this means that the electrons will collide with the atoms half the amount of times. Also if the length of the wire was trebled or quadrupled then the resistance would also treble or quadruple.
Evaluation
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. If I were to repeat this investigation I would use pointers instead of crocodile clips, I would do this because pointers would be more accurate. The pointers would be more accurate because the tips have a much smaller area than the crocodile clips giving a more accurate measurement of the length of wire. I would also improve my Investigation by testing the same wire but with different widths of that wire. I would do this to expand on my Investigation.