Resistance (Ω) = Voltage (V) / Current (A) or R=V/I
I’ll move the lead up to the next interval, the 10cm marker and record and work out the results from that. I’ll continue this until I have results for all 10 intervals.
To make sure that my investigation is safe I will stick to the 4v limit and not use anything higher. Also I’ll be careful when putting a current through the shorter intervals. The resistance can be so low here that the wire heats up and can snap.
I’ll make sure that I keep the investigation fair by keeping the voltage the same on the power supply throughout. The length of the wire which I will send the current through is all I will change. I will use the same equipment for the whole experiment. I’ll keep the temperature, thickness and material the wire is made of the same.
We carried out an experiment to determine which factors affect the size of resistance. We discovered the longer and thinner the wire the higher the resistance. Also using Nichrome wire instead of constantan increases the resistance. I will be keeping all other factors apart from length the same to establish the relationship between length of wire and change in resistance.
I could also investigate these other factors: the temperature, material and thickness. But we have chosen length to measure because it is the easiest to create many variables for and so we get a larger scope of results.
I will make 10 measurements each 5cm apart; this will give me 10 different results. I will repeat the whole experiment to give me two sets of results; I’ll then take an average from the two sets of resistance results and plot a graph with those. This will make the results more reliable.
Results
Table of Results
Analysis
As the length of the wire was the increased the resistance also increased.
The line graph which follows is a diagonally north/western facing line, showing a steady increase in resistance against wire length. This is because the charge has more atoms to pass through. The further the current has to travel the more collisions it encounters on the way; this is how the resistance is formed.
These results as supportive of my prediction, and confirm my guesses of the outcome of this investigation.
Evaluation
The method I used worked well and was easy to use to get the results I wanted.
A problem I encountered when using a very short length of wire was that the resistance was so low that wire’s temperature rose very high because of this it was dangerous as well as difficult to try and get a result for the 5cm readings.
The results that I obtained during the investigation were fairly accurate for the equipment I was using. The difference between the first and second sets of results was worrying, but it levelled out and when I took an average it seemed okay.
I could have used a more a accurate voltmeter and ammeter with a more precise scale due to some measurements being very close together, between two figures.
If I was to repeat the experiment I would use a different material of wire which may cope better with low resistances and not heat up to rapidly.