The apparatus that I am going to use in my main experiment are as follows
- Volt meter
- Ammeter
- Crocodile clips * 2
- Pliers
- Metre ruler
- Connecting wires
- Power supply
- Constantan wire
These apparatus will be handled with care, as it is important that I set it all up correctly and safely.
I want my results to be extremely good, and just the way I predicted them to be. The information and the results that I am using is first hand experience. I am going to do each experiment and then place my results into a table. The reason I put these results into a table is simply because it is clear to understand and is much neater. I will use my results to make predictions and make graphs. This will help me compare results. Comparison of results is vital because it is important to see which reaction was fastest, and again this is important because then I can make a conclusion, discussing why a certain experiment was faster than other experiments. When I do the experiment, I will be prepared with my results table, so all I have to do is to read the readings of the voltmeter and ammeter and then place the digits in to my organised table.
To make my experiment a fair test, I intend to do everything the same. I can’t use the same lengths as this is one of my variables, but I want to use the same setup every time I do a test. What I mean is that the apparatus have to be the same for each test, because this would be unfair. Equipment has to be the same, you cant use one normal voltmeter which is brand knew, and then for the next experiment use a slower voltmeter, even though voltmeters should all be the same, there can be errors in the equipment it self. It should be very fair when I read the numbers off the screen. Though somewhere where I need to be more careful is when I cut the constantan wire to there measurements. It needs to be accurate so it is fair. Accuracy needs to be realised throughout the experiment. For it to be a fair test, when I make comparisons, I do it correctly for the right experiments. I hope I don’t make any errors in my work because it is important that the tests are done fairly in order for conclusions to be correct.
Accuracy was mentioned above, but I need to state the fact that without accuracy, conclusions can’t be correct. I need to be accurate when cutting the wire, making sure that it is the correct measurement and not a cm over either way. Accuracy is also needed when I set up the experiment; it needs to be correct and done efficiently so work can proceed quickly. The last place where accuracy is fundamental is when reading the numbers. I need to take down the exact numbers, so the results are accurate enough so a conclusion can be drawn up.
I have chosen to do two variables. My first variable is to change the length of the wire. This is again giving me a wider range of results and also I will have more tests to base a conclusion on. The way I am going to change the lengths is by, with the pliers cut a wire 1 meter long. Then do the test for 1meter. Then cut 10 cm and I will repeat it all the way to 10 cm. My second variable is by changing the widths of the wire. This experiment is different from the other ones. The way I intend on doing this is by using different wires, with different widths. One may have 36 SWG and another only 28 SWG. I will then compare the widths with widths, and the lengths with lengths.
Below is the blank table, this shows how I am going to set out my results.
Background knowledge
For this part of my coursework I am going to discuss a few things that affect or play a role in the experiments that I am going to do. There are many things that affect the growth of a plant, like sunlight and oxygen levels. In the same way my experiment has things involved in it which I would like to talk about.
The first topic I am going to talk about is the things I am using. Ohms law is a big discovery made a long time ago. Firstly we need to know what ohms law is?
Ohms law is a definition which helps us to discover the resistance of a circuit.
Ohms law simply states –
Resistance = voltage
Current
Ohms law consists of three things
- Voltage
- Current
- Resistance
Now I will explain what each of these mean
- Voltage - Voltage is an electric potential difference between two points on a conducting wire. Voltage is measured in volts. Voltage comes from various sources. Two examples of these sources are batteries and electrical outlets.
- Current - Current is measured in amps. Current is charged particles which flow from the voltage source through conductive material to a ground.
- Resistance - Resistance is the opposition that a material body offers to the passage of an electric current. Resistance is measured in ohms. Examples of items with resistance are light bulbs, hair dryers, toasters.
The reason for resistance coming about is very simple. When there is a force on way, there is always a force working the opposite way. This is like are muscles, one is contracting and the other relaxing. Also when you drop out of the sky, gravity is pulling you down, and air resistance or up thrust id acting against you. In the circuit, current is flowing one way, and what makes it slower, resistance. Resistance is slowing something down, a force acting against you, and all ohms law does is justify and state this simple law of resistance.
Resistivity is simply the amount of resistance a circuit can handle, otherwise known as bulk resistivity.
The range of my work is good, because I believe I have different sets of data. The good thing is that they are all varied from one another, they are all different. The thing with having different amount of data is that more comparisons can be made, and a greater expertise of conclusion can be made. It is important that when I am working, that my results are sufficient enough to base a conclusion on. The conclusion has to be accurate, and having a greater range of results is good, as I can identify any anomalies and make an accurate conclusion with the data where there are no errors. I can only do this if I have more data to work on, so I believe that I have done enough work so if any errors appear I can work around it. I think my experiment will be good and exciting, as the results will provide good solid data, which I hope is error less.
As a conclusion, I can say that my preliminary experiment went very well, and I am looking forward to my main experiment because I want to see if my results turn out the way I wanted it too. Now I will tell you what I think will happen. I predict that for my second variable, using width, I think the resistance will be the highest for the thinnest wire, which in my case is SWG 16; it will be interesting to later on see if I am correct. For my other variable, consisting of length, I predict that the highest resistance will come at the longest wire. My predictions went just guesses; I am going to explain why I think what I think. I believe that the thinnest wire will have more resistance, because I think that there will be a smaller surface area on the wire, resulting into more resistance. What I am saying, the bigger the area, the less resistance, as there is a larger surface area to cover. For length, I predicted this to happen because I think the longest wire, which is 100cm is spread out, resulting larger body area, so there would be more resistance as it is long and thin, whereas the shorter ones, would have less, also because there is not enough time for all the particle energy to be stopped, as the length is small, and it travels very fast, so the particles would be hard to stop, so the resistor wouldn’t be as effective.
In conclusion, I believe I have made suitable comments about my preliminary experiment, and believe my main experiment will go just as well, if I work hard and follow instructions. I also think that I have made and detailed my experiment very carefully, and not forgetting details which could lead to inaccurate results. It is important that I continue to follow the steps I have laid down. I have made a suitable prediction backed up with my background knowledge, and my plan is good, and with hard work, I should be able to achieve good and satisfactory results.
Obtaining evidence
This is the stage where I have completed my experiment. I now want to talk about my work and mention how I did my works. This stage is important because I need to compare of how I said I would do the experiment to how I did do the experiment.
A recap of the apparatus I used are listed below (for the main experiment)
- Volt meter
- Ammeter
- Crocodile clips * 2
- Pliers
- Metre ruler
- Connecting wires
- Power supply
- Constantan wire
This is how exactly I did my experiment. I first cleared my table from all the unnecessary books, and then got all my apparatus out which I was going to work on. I simply then started to make my circuit. I was very careful when plugging the power supply in, ensuring that the health and safety of my group was never in risk. Then once the equipment was set up, I started to test my experiments. I got different wires and cut them into different lengths, and then placed both ends on to the crocodile clips, and then I switched on the power supply, and quickly before the power supply was over heated I read the readings off the volt meter and the ammeter. I did this for both my variables, which is important. I kept the whole experiment the same, this was important for the test to be a fair test. I can say that my experiment went very well; I think I did everything fairly and accurately. I can also add the fact that me or any of my group, led the whole experiment safely, and did not break anything and altogether very focused and that is why we have very accurate results. We worked together all the way. Before we started the tests, I had blank tables ready so all I had to fill out was the digits. This was very helpful, as it saved time.
I have listed below the results that I obtained; these results were obtained from first hand, and all in the class. The results are for both variables, and are indicated very clearly, which is for which variable. Also below that I have added a few explanations to help you understand the recordings. I will also like to add, that when I worked out the resistance, I used the formula: Resistance = Voltage/ Current. All working out has been rounded off to three significant figures.
Results
Variable – Length of Wire
C40
SWG – 32
Diameter/Thickness – 0.28mm
At 2 Volts
C38
SWG – 36
Diameter/Thickness – 0.20mm
At 2 Volts
C44
SWG – 24
Diameter/Thickness – 0.56mm
At 2 Volts
C42
SWG – 28
Diameter/Thickness – 0.40mm
At 2 Volts
C41
SWG – 30
Diameter/Thickness – 0.31mm
At 2 Volts
Below are the results for my second variable, this is the thickness or the width of the wire.
Variable – Thickness of a Wire
All these experiments were done at 2V for safety reasons, using a silver wire each time to make the results fair.
I believe that I have enough data to make a conclusion; this is because I have chosen a wide range of wires to test on giving me more data. I believe that I made my test accurate by doing tiny things to my work to make it better. For example, I was extremely precise when cutting the wire to its exact measurement, so I was very precise. This would have been an unfair test if I wasn’t accurate and decided to measure free hand. That is just one example of why accuracy is vital when it comes to finding results.
I consider the results very clear, and it is easy to read. It can be interpreted and understood easily, all because the tables are clear and easy to read. I also believe that my experiment with my group was very precise. The variables are suitably and are adequate enough to the investigation, because it is a way of measuring the resistance in a circuit, and I am investigating the affects of material on the resistance levels. Precision was very important, and I think we did great when it came to precision, because we have been accurate, and haven’t made too many errors, if any.
In conclusion, I have clearly outlined the results I obtained from my tests; this has been placed in an easy table. I would like to add, that we have a good range of results, all from are two variables, length of the wire, and the width of the wire. The results are what I expected to be, I will goon to explain what the results show and mean. For now, my work has been displayed in the correct manner, and my accuracy and precision has resulted in to the good results I have achieved.
Analysing evidence
In this section of my coursework, I am going to have a few graphs. I make the graphs from my results in the table. I will then explain what the results show, and I will explain how I got the results.
My results are listed below.
Results
Variable – Length of Wire
C40
SWG – 32
Diameter/Thickness – 0.28mm
At 2 Volts
C38
SWG – 36
Diameter/Thickness – 0.20mm
At 2 Volts
C44
SWG – 24
Diameter/Thickness – 0.56mm
At 2 Volts
C42
SWG – 28
Diameter/Thickness – 0.40mm
At 2 Volts
C41
SWG – 30
Diameter/Thickness – 0.31mm
At 2 Volts
Below are the results for my second variable, this is the thickness or the width of the wire.
Variable – Thickness of a Wire
All these experiments were done at 2V for safety reasons, using a silver wire each time to make the results fair.
What my graphs show.
In my first graph, I have used two different wires. I used
SWG 32 diameter 0.28mm
SWG 30 diameter 0.31mm
The graph clearly shows that one of the wires has produced more resistance than the other. I can conclude that the wire which was thinner, and had a smaller diameter. This says that the bigger the diameter than the less resistance produced, or, the smaller the diameter, the bigger the resistance. This entire conclusion can be observant from the graph.
The statement concludes, the bigger the diameter, the smaller the resistance.
For my second graph, I have done the graph with my second variable, which is width against resistance. From the graphs we can automatically see positive correlation. On this graph, we can see that the bigger the width, the less resistance. So if the width is very small, than there would be more resistance.
The statement concludes, the bigger the width, than the less resistance.
Conclusion
I want to now look back at my prediction and just mention if I am correct with my hypothesis or not.
I said earlier that the resistance will be the highest when it is at its lowest width which was SWG 16. I am wrong in saying that, because when I did the experiment, I found that SWG 16 had the least amount of resistance, and it was actually the other way round, so SWG 40 had the highest resistance. This is probably because there is more area, so resistance is spread over, so I was wrong earlier thinking less area had more resistance, I have learnt from this and now understands why a larger surface area would have a larger resistance.
For my other variable I said the highest resistance will come at the longest wire. This hypothesis was correct; I found from all my graphs that 100cm produced the most resistance. This means my explanation of it have a larger area is correct, so this explains that my graphs are accurate and correct.
Evaluation
This is the final par of my coursework, this is where I will look back at the work I have done, and see where things could have been differently. I think the way I did my coursework was pretty good, because it was specific to what I wanted. I needed to investigate the resistance levels of certain subjects. I consider that I have done what the criteria has asked for, and are work was through and neat. The work and experiment were relevant to each other, this was good, and because this means that I have done work which does affect what I am looking for.
The procedure I use I think was very suitable, because it was very precise and clear. Finding the resistance levels helped us to analyse the data. We could see which data affected the level of resistance, and others which had no influence at all. The method I used was testing the levels of resistance by setting up a circuit, placing the wire into the crocodile clips and then using the figures from the volt meter and the ammeter, I used Ohms law to convert the numbers in to resistance, so I think this was pretty simple and I was easy to understand.
I think the quality of the evidence is very good, thankfully I can say that I did not make any errors, therefore I can say that there were no times were I needed to identify any anomalies. I did not make many errors at all through my work, so it was a satisfactory experiment.
I believe that my experiment was suitable as I said, but there are ways that maybe I could have improved on it. For example, I believe that if I had repeated my results just one more time, then possibly I would have more data, then I can compare using the same method, but this time I will have more to compare with.
I think that my method of analysing and results were reliable, because they justified the system as the results I got, I made substantially longer. I would like to add that I did my coursework very well, and it went well towards my predictions. The positive correlation in the graphs was something I wasn’t expecting, so things like this was good, as it was different.