Equipment Used:
*A Metre Ruler
* A Volt Meter
*A Ammeter
*Nicrame Wire
*2 Crocodile Clips
*Power Pack
I Predict that from prior knowledge that the longer the wire the higher the resistance, I think this is because there will be more atoms inside the wire and more collisions. Therefore a shorter piece of wire would have fewer atoms and fewer collisions making it have less resistance. I will now check if my prediction is correct by commencing with the investigation.
Method.
- Firstly I will gather all my equipment and set it up.
- I will then check that all my equipment is set up correctly and that it is not a short circuit. This makes it a fair test.
- I will then place one end of the wire on the ruler at 0cm and stretch it out to 60cm; I will then cut it at 60cm with wire cutters.
- I will then turn on the power pack at 4 Volts.
- I will then record my first set of results for the ammeter and voltmeter.
I will then switch the power pack off so it avoids over heating.
6. I will then repeat this 3 times changing the length of the wire every 3 times.
7. While doing this I will always check that the equipment is in place and not
broken before switching the power pack back on.
8. I will check I have all my results recorded in my table and turn off my equipment and put it away.
9. I will then view my results and work out the averages.
10. I will then place the average resistance of the wire on a scatter graph and create a line of best fit.
11. I will record the points that did not fit and see what might have gone wrong.
12. From my results I will make a conclusion and see if my prediction was correct. I will also state what I could improve and extend my experiment further.
Symbols.
Equation. - To find out the resistance for my results.
R= V Voltage
I Current
Results Table for my Preliminary results.
A Scatter graph to show the results obtained from the preliminary experiment.
My preliminary results show a negative correlation, the points do not fit my line of best fit, there is a slight pattern but there are a few random results that do not fit the line. Also this graph shows that the longer the wire the less resistance but I do not believe this so I am going to repeat the experiment. Making sure that the experiment is a fair test and does not go wrong.
Results table from experiment.
A scatter graph to show the resistance of a length of wire.
Analysing my results.
Observation: looking at my graph I can see that all my points fit the line of best fit; this proves my experiment was successful and shows a strong positive correlation. There are not any anomalous results.
Evaluation.
I felt my experiment went really well, I encountered problems while completing my preliminary experiment, this including not making sure the current was the same throughout, looking at my results and after re- taking the experiment I realised my mistake of not always checking the current was the same throughout. My results are very close together which is evidence that my results are reliable. There is a general trend in my graph which proves my prediction is correct. It shows that the length of the wire effects the resistance, the longer the wire the higher the resistance.
Conclusion.
My results support my prediction, after seeing my results being successful I realise that my method was suitable and a reliable way of testing the resistance of a wire. I can see that my results go through the line of origin which shows that the room was a good temperature, not too hot or too cold which could have affected the results.
The one aspect I found difficult was the fact that the wire was not very thick so it curled; I would if able to repeat this experiment, change the type of wire to a straighter one.
I was not limited to time I would of liked to re-done the investigation, just to make sure once again that my results were correct. If I were to change the experiment I would have liked to of used a micrometer to measure the thickness of the wire along the experiment just for fair testing procedure, so that it is not different at different parts of the wire.
To extend my experiment further I would have used a OHM meter, this measures the resistance without having to work out the average divided by the current, this world save me time so I would be able to re peat my experiment and get a 3rd set of overall results. I would also of liked to further my results by testing more measurements of the wire then record them on a graph, maybe even making my wire as long as 10meters or as small as 1 cm. I would then see if this would still comply to the longer the wire the higher resistance rule.
I believe that the more I test the theory of the resistance of a wire the more I am able to understand how variables effect the resistance. I feel that if I had used an ohm meter the results could have been more accurate and I would have had the ability to check my previous result.
Looking at my results I can prove my prediction was correct, the shortest length of wire (10 cm) contains the lowest resistance while the longest length wire (1 meter) shows the most resistance.
This is because as the length of the wire increases, the amount of metal atoms that are inside the wire- for the electrons to pass through to reach the end increases so the electrons will be slowed down, making the journey longer.
The electrons have further to travel in a longer piece of wire so it is harder to reach the other end, therefore more collisions occur which increases the resistance. In a shorter piece of wire there are fewer atoms, making the path for the electrons easier, not making as many collisions, therefore there is less resistance.
This diagram shows a longer piece of wire, containing lots of atoms, and a shorter piece of wire which contains a fewer amount of atoms compared to the longer piece.
Overall I have found this experiment a success, I have collected all my results I needed with ease and it was quite an enjoyable experiment. I am glad my prediction was proved correct and I obtained accurate results. If I could repeat this investigation I would have defiantly kept the variables the same but maybe included an ohm or extended the length of the wire idea.
