This is the table I will use to plot my results in:
Method:
I will attach a crocodile clip to one end of the wire and will put the other crocodile clip 10cm along the wire. I will then record readings from the ammeter and the voltmeter. I will move the wire along to measure the amps and volts at 20cm, 30cm, 40cm, 50cm, 60cm, 70cm and 80cm. After I have completed all these readings I will repeat the whole experiment take all the readings again.
Apparatus:
- 1m wire
- Power pack
- Crocodile clips
- Ammeter
- Voltmeter
- Ruler
- Wires
My preliminary work was to perform a dummy run. I did a practice version of this experiment to see how it worked. These are the results from my dummy run:
Below are some of the problems I encountered in my dummy run:
- I used quite a short piece of wire this caused the wire to become very hot increasing the resistance. This stopped it being a fair test because the temperature did not stay constant
- The results reached there maximum resistance this will hopefully also be solved by a longer wire
- To solve this I am increasing the length of my wire from 80centimetres to 1metre I will take results every 10centimetres.
The only change I will make to my method will be to take two more readings at 90cm and 100cm. I will make readings at 0cm, 10cm, 20cm, 30cm, 40cm, 50cm, 60cm, 70cm, 80cm, 90cm and 100cm.
To make this experiment a fair test I will only change the length of the wire I will not change anything else. I will keep the wire the same thickness because if the wire is thinner there is less room for the negative ions to flow. The wire will be made of the same material throughout the experiment. I will keep the voltage the same and I will keep the wire at room temperature throughout this experiment because if I change the increase the temperature then the positive ions will move about more making it harder for the negative ions to pass through. To make sure my results are also fair I will repeat the experiment and take all my readings again.
Attempt 1:
Attempt 2
To find the resistance I
Average results:
I can see that the resistance increases, as the wire gets longer. You can see that it is directly proportional as at 10cm the resistance is 1.2ohms and if you double 10cm you get 20cm and the resistance of 20cm is 2.4 ohms, which is twice the resistance of 1.2 ohms at 10cm.
I have got a straight-line graph going through the origin. My graph is directly proportional the resistance doubles when the length doubles. The line goes through the origin. On my graph I have drawn lines in so that you can see how the graph is directly proportional and that the resistance of 40cm is double the resistance of 20cm.
My prediction was correct as the resistance increases, as the wire gets longer. The line goes through the origin and the resistance is directly proportional to the length.
When a charge flows through a wire they get slowed down when they hit positive ions this generating a lot of heat this slowing down of electrons is called resistance. A charge is a flow of negative ions. As my wire gets longer the resistance increases when I double the length of wire the amount of resistance also double as there are double the amount of positive ions. The line of best fit will go through the origin because when there is no wire there cannot be any resistance.
I think that the experiment went very well as I got good and accurate results. I have proven that the resistance increases, as the length of the wire gets longer.
My points all fit accurately onto my line of best fit. This shows that I do not have any anomalous results. My method was able to produce accurate readings as you can see by my lack of anomalous results. There are no gaps in my graph.
To further improve the accuracy of my results I could take readings every five centimetres and I could take readings from 0cm to 200cm. This would mean I have a bigger and more accurate range of results. I could also leave the wire for a few minutes after each reading to make sure it cools down to room temperature. I could also make three or four readings at each length.
My graph is reliable because all the points fit onto my line of best fit and my graph is directly proportional and it goes through the origin. I do not have any anomalous results that don’t fit onto my line of best fit.
To further investigate resistance I could repeat the experiment but changing the heat and keeping the length of the wire constant or I could change the amount of volts I pass through the wire.
Ben Wilkinson 11PA