In this experiment we are trying to find out if by changing the length of a piece of wire its affects the resistance of current.

I will find this out by having a piece of wood with a piece of wire stretching along the wood. I will have a power box on connected to an ammeter and voltage meter and then these connected to the piece of wire using crocodile clips. The variable I’m going to change will be the length of wire.

We can have the wire from the length of 1cm up to 100 cm’s long. We can use the crocodile clips to make the wire long or short. The equipment I will use is:* Crocodile clips* Power Pack* Wires* Variable resister* Ammeter* Voltage Meter* Wood with a piece of wire clipped onto itI chose the equipment I have because I think that it will be the best to use this so it will measure it accurately and give good results.

To measure the Variable which I’m changing I will have a piece of wood with measurements written onto it so I can use it to mark where I have to put the crocodile clips so it is a accurate measurement. The variable I’m trying to measure is the resistance. The resistance is a current that flows through the wire when there is a current running through it, I will have an ammeter and a voltage meter to read the resistance. I will be making my investigation a fair test by using the same equipment each time i.e.

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the same piece of wood with the measurements on it.I will also wait until the measurements on the ammeter and the voltage meter are not flickering so I can read then and they are still and not in-between numbers, this will hopefully help me get an actuate reading. I will try and do the test for each length four times so I get another actuate reading.

There are some things that might make the test go wrong and give me an inaccurate readings, such as if the door is open in one of the four times I do the test, that result might be higher resisentence or lower, the room temperature might change as well during the test but I can’t control that. The only way it could be the same things is if I did the experiment in a small area and I could control the temperature the test was being done in. This is how my experiment will be set up:I predict that the more wire I use on the wood stick, then the more resistance I will get travelling through the wires and the reading on the ammeter will be high for the long lengths and short for the short length of wire. I think this because the more length there is the more energy that will travel through it, then the readings on the ammeter and voltage meter will be high.The variables that could effects the tests are the room temperature, which I can’t control. The heat of the power box I can control, by turning the box off at the end of each test and letting it cool down for a bit because other wise I might slow down the energy due to over heating. Another thing that might affect the test is the length of the wire which I connect the circuit together with. I cannot get the wires the same length because I cannot cut the wires so this might affect my results a little bit but not a lot.

Another thing I could do to make it a fair test, I could check that the power box, ammeter and voltage meter is working properly each time. One more thing it is important because I don’t think you can control this unless you measure it all out.The crocodile clips are wider in length, so when you put them onto the measurements you want, on the wire it is not perfect on the measurements on the wood. So each time you take a result it is either less then what you want or more then you want. The only way you could possible control this is if you measured the width of the crocodile clip and measured the distance form the wire and not then I don’t thing you could get it exactly perfect. So one time you do the results you might get the crocodile clip on the right spot and another time you might get it way out of line with right measurements. I think that if you keep to all these and try and control all of the variables that can effect the investigation then I might get a good set of results that I can use in my graphs etc.

I will collect four sets of results that are near each other in some ways like in decimal points if I round them up, this should mean they are near enough right.The measurements I will take are the length of the wire and how it affects the resistance and the voltage against the current; I will show these results in a table and in a graph for each one. When I’m doing my test I will make a not of where the slider on the resister is so when I do my test again I can change it or leave it the same.

I will do this so I can compare the results for each other set of results and see what ones changes the resistance the most.I found a few problems when I did the test. The first power pack I used didn’t work so I had to change it.

It was confusing because the wires overlapped but then I found out that u could change the wires round so they were straight and I didn’t get mixed up. I also found that the crocodile clips wouldn’t stay on the wire probably, they would slip down the wire and they would not stay on straight so this might have interfered with my results because the measurement wouldn’t have been accurate. To find the resistance, I had to use the voltage and divide it by the current (v a = )Length Of Wire (cm)Current (a)Voltage (v)Resistance0 – 40 cm0.130.584.460 – 50 cm0.120.

625.160 – 80 cm0.100.757.50 – 100 cm0.100.800.

80The results above are the set from my primarily test. It shows all the results vary, there could be something I have done wrong. The current and voltage are in the same decimal place but the resistance shows they can vary. This might so a variable have changed that I haven’t controlled. In my set of results from where I do four separate tests for each length I will work out the average from the results.The TestLength (cm)Current (a)Voltage (v)ResistanceAdverae0 – 40 cm0.

080.140.150.

350.350.400.321.194.83.

33.53.5A= 0.18V= 0.640 – 50 cm0.090.

130.140.300.

350.520.531.213.94.03.84.0A= 0.

17V= 0.700 – 80 cm0.070.100.110.200.

500.680.691.292.16.86.36.

5A= 0.12V= 0.790 – 100 cm0.060.100.

100.100.920.760.781.300.

557.67.87.

2A= 011V= 0.85I have done my experiment safely, I have made sure that the wire and power box haven’t got any other power going into it and I have made sure that I haven’t over heated the wires so that the wire on the piece of wood hasn’t burnt. In the table above it shows my four repeated tests for each length of wire. The results were not all the same but they show that I have done the experiment carefully. I know that I have collected enough results because there is a fair number for each length and I can divide them, (the voltage and current) to get enough answers.I have made changes to my investigation because I have redone my test again, but this time I did it four times instead of three. I made sure it was a fair test by doing everything I said I was going to do in my plan.

I tried to make made precise measurements by trying to get the crocodile clips as close to the measurements on the wood piece as I could. I also made sure the right number on the ammeter came up so its didn’t flicker and it stayed on one number for more then one second. I have found out by doing this experiment that there are a lot of variables that could make the results be different then the results if you could control everything that could change the results.On my graphs it shows that if you double the length then you double the resistance, in some cases this will work but in others it doesn’t.

My plan shows sensible way of testing my prediction because, the line on my graph shows this aswell. The line on my graph goes up in a straight line to show how the length of wire affects the current’s resistance. You can use my graph to predict results for similar test like this in the future. My results in my graph show that resistance can be changed by anything that can affect the current or resistance.My perdition was correct because my results show the higher the measurements are then the higher the resistance of the current should be.

My experiment was accurate because I made sure that all the things that could affect my investigation I controlled. None of my results were odd really they all made a line that wasn’t in a curve so they didn’t stand out or nothing. If I did have some odd result I would have got these by making a wrong mistake on one of the test or even the length of the wire could have changed for one test. The most difficult part of the test was recording all the results, because I did four tests for each length then it made it harder for me because I had to wait each time for the power box n wires to cool down, (this was for safety). I could improve my experiment next time to make it more reliable by maybe having more time do it because then I could leave it a certain amount of time each time so that I could have let it cooled down say for 2 minutes after each test, so the temperature decreased.If I ever did my test again then I could improve it many ways. I could have more time so I can do it a bit more slowly so I can get accurate result for each test. I could also make sure the wires the same length and this would make it fairer and maybe give me a different set of results that were clear and that had a pattern.

I could also make sure that the temperature of the wires and power box etc stayed the same throughout the tests I did. I would start by making sure the crocodile clips were put on the wire with accuracy so they didn’t slide up or down the wire when I was making the readings. I would use a different variable that I could place the wire onto that I could also write the measurements like 10 cm and 20 cm onto, I could use a rule instead of writing it onto the wood.My conclusion after I have done this experiment is that a lot of simple things can change the state of resistance everytime you do the test.

You would have to have everything clipped to one another with different variables to make it a really accurate test then you even might have a few things that will make a few odd results on a graph.