Fair test
In order to get a good set of results the tests will have to be fair. To make this experiment a fair test we will need to keep some points the same although some will obviously change. Parts that we will need to keep the same, the voltage is one of them. It will always stay the same although we need to change the length of wire to see how the resistance changes. Although the changes in the resistance will hopefully provide a good interpretation to which factors affect the resistance.
Another point that will not change is the temperature in which its done, room temperature is the temperature it will always be done in.
Equipment
1-meter long wooden ruler x 10
one meter of nicrome wire
2 crocodile clips
connecting wire
Power supply
Voltmeter, Ammeter
Variable resistor
Safety
Obviously the most important thing whilst using electricity is keeping everything dry as water and electricity do not mix. Another safety point would be not to also touch the wire while the experiment is going on.
Prediction
I predict that as the length of the wire gets bigger so will the resistance. This means that the current will go down because the current will have more electrons flowing meaning more collisions.
I predict that when the nicrome wire is placed into the circuit, the resistance will stay the same. This is because the electrons within the nicrome are held tightly together by strong bonds, meaning that the electrons are broken apart at a much slower rate by the current. Meaning the current will take longer to flow all the way round the circuit. I predict that as the length of wire increases then the resistance will also increase in proportion to the length. I think this because the longer the wire the more atoms there will be and so it is more likely that there will be more collisions. Therefore, if the length is doubled then the amount of atoms will also double resulting in twice the number of collisions slowing the electrons down and causing more resistance. My graph should show the pattern that shows how length is directly proportional to resistance; this is proven by the positive correlation found on my graph hopefully. I believe that my results graph will look something like this.
Positive Correlation
Method
First a length of wire is put over a meter long ruler, then it is sellotaped down. The positive crocodile clip is attached at 0cm. And the negative is moved up and down the wire, stopping at 10, 20, 40, 60, 80 and 100cm. Each time reading the ammeter and voltmeter to work out resistance R = V/I. This is using nicrome wire. Other variables, voltage, thickness, and temperature will be kept constant, although the temperature will rise once current is passing through it, which will cause the atoms in the wire to vibrate, and so obstruct the flow of electrons, so the resistance will increase because the electrons will be bumping into the moving atoms. Basically once all of the equipment is set up the power will be turned on with the crocodile clips set to 0 and 10, the readings will be taken (from the ammeter and voltmeter) then the ruler will be swapped and the same done again until we have five results. Then after this the crocodile clip will be moved along to 20, 40 and so fourth until I have all of the results.
Variable Table
Number and Range
I will be using a range of five readings for each length of wire; this means I can either use the average or the most common reading. I will also be taking measurements from 100mm to 1000mm pieces of nichrome wire. This will start at 100 and go up by 100 each time. I’ll record all of the values for resistance up to 3 d.p (decimal places), although the ammeter readings will be to 2 d.p.
Results table The underlined values are my averages.
Average resistance= 5.546
Analysis
In my findings in this experiment I have noticed that the longer the piece of wire the more resistance will happen. This is because all of the electrons use up more of their energy moving along the wire. So the longer the wire the more energy they lose, causing resistance.
This diagram will help explain what I found out.
= atoms
= electrons move from negative to positive
The electrons carry the energy; they give it to the wire in the form of heat energy. Then the electrons return to the power supply to refill with energy.
Also ohm’s law states that as you increase the current flowing through the resistor, the voltage will increase. Voltage is proportional to the current, although for this to work the temperature must stay the same.
The tables results were worked out by using the formula for getting the resistance, this was acquired from rearranging the formula for getting the voltage.
Resistance is a force, which opposes the flow of an electric current around a circuit so that energy is required to push the charged particles around the circuit. Resistance is measured in ohms. A resistor has the resistance of one ohm if a voltage of one volt is being given if one amp is required to push the energy through it.
These collisions slow down the flow of electrons causing resistance. Resistance is a measure of how hard it is to move the electrons through the wire. If the wire length is increased then the resistance will go up, this is due to the electrons having to travel a further distance and so more collisions will occur. This means that the amount of resistance given should be directly proportional to the length of the wire. This is why I have chosen to investigate on how changing the length of wire will affect the amount of resistance calculated.
The formula for resistance is V
I
Next I will display the graph which contains the results from the experiment.
In this experiment I decided to keep the variable resistor in, this may have made my results slightly different. However through checking my results with my friends I have found that my resistance results are correct. My voltmeter and ammeter readings were different but if my resistance calculations are the same then it doesn’t matter because ohm’s law is still working and giving me the correct reliable results.
The graph has been set out in a way so that across the x-axis is the independent variable (length of wire) meaning it doesn’t change and up the y-axis is the dependant variable (resistance) meaning it doesn’t change.
Once I had finished the graph I noticed that it had a positive correlation, basically it was showing the pattern of how if the resistance went up so did the length of the wire. Obviously this is the pattern which shows the relationship between the length of the wire and the amount of resistance accumulated by the different lengths of wire.
The data which I had collected seemed fairly reliable and this was justified when I checked it with my friend’s results, my results from the ammeter and voltmeter may have been same but our calculations for resistance were very close. This meant that even though our readings may have been slightly different the resistance was overall the same which meant my results were still correct.
Conclusion
At the end of this experiment I would say that it has gone fairly well the results all came and so did the scientific knowledge. Ohm’s law also played an important role in the relationship between the resistance and the length of the wire. While moving through the wire, the electrons have to squeeze together. This is because there is not enough space for them to pass evenly through. The more the electrons have to bump together then the higher the resistance. This is because it will take longer for them to pass from one side of the wire to the other side. This is because the current is slowed down. (The longer the wire, the longer the electrons have to stay squashed together and so the longer they take to pass through the wire and the higher the resistance). The experiment’s conclusion is really looking at which factors played a higher part than the others, however within this experiments certain factors were consequences of other factors.
Through looking at my graph I could already see that there was obviously a correlation between the length of the wire and the resistance, the scientific knowledge I just mentioned proves this. The longer the wire the longer they stay packed the more they bump into each other, this is what caused the positive correlation.
Within this experiment certain factors were not really investigated although the scientific knowledge had already given me an answer, two examples of these would be the different widths of wire and types of wire. Density has a large affect on the amount of resistance. The resistance depends upon the amount of denseness e.g. a large surface area has less resistance because a small area has tightly packed atoms which in turn rebound many of these electrons. Then also certain metals are better at transferring electrons than others. Even though there were some points within this investigation that didn’t get looked at there was still enough evidence collected to make a solid conclusion.
Evaluation
In this experiment I have come to the conclusion that there is obviously a pattern concerning the factors of the resistance and what really causes it.
From my results and scientific knowledge I have come to the conclusion that as the piece of wire gets longer the resistance gets bigger.
I feel the experiment went fairly well although some aspects I feel could be improved and changed for the beneficial status of the coursework. My results seem fairly secure and safe because they agree with the scientific knowledge and so it must be correct. I managed to keep the temperature the same as it would have affected the results through the consequence of the atoms vibrating. The results which I was able to obtain were not perfect; there has have been no visible patterns except for the pattern that the collision theory gives. However my results are very similar to my friend’s results which gave me the idea that if these results can be so near than there must be some sort of pattern. This is what helped me in seeing if whether my results are reliable.
If I was going to do the experiment again I would this time look at getting the rubber plug in a bit quicker so that the gas can be collected quicker and more easily. This would hopefully show some sort of improvement in my results. The evidence I have so far does still match the collision theory and this is what matters because it helps support my conclusion which was basically agreeing with the found factors in the collision theory. The results each time went up as the concentrations went up because there were more particles in the acid. As previously explained in my prediction and analysis the scientific knowledge justifies the pattern or correlation in the results. As long as my results justify the scientific knowledge then there isn’t anything else to look at than whether if I could improve the experiment if done again.
Parts that I would change would be the actual method because hopefully this would improve the overall results and immediate findings; I have already spoken of the bung problem although there are some other parts or factors which I would have used to give the investigation more depth. However for now I am happy with the results and feel that the scientific knowledge has justified my conclusion and findings.
By
Ben Pilgrim