2. When we weren’t running the experiment we made sure that we kept the current.
3. We made sure that the ice didn’t melt on any of the electrical equipment.
4. I will handle the power supply carefully.
5. I am going to only use a voltage of 2 volts.
6. I will be careful when handling live wires.
Prediction
Resistance occurs when the electrons traveling along the wire collide with the atoms of the wire.
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.
Based on the facts written above I predict that if the length increases then the resistance will also increase in proportion to the length. I think this because the longer the wire the more atoms and so the more likely the electrons are going to collide with the atoms. So if the length is doubled the resistance should also double. This is because if the length is doubled the number of atoms will also double resulting in twice the number of collisions slowing the electrons down and increasing the resistance. My graph should show that the length is proportional to the resistance.
Scientific Knowledge
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. The circuit itself can resist the flow of particles if the wires are either very thin or very long e.g. the filament across an electric bulb is quite thin as needs to resist the flow of particles for the bulb to glow.
There are certain factors that affect the resistance of a piece of wire they are:
1. Temperature: If the wire is heated up the atoms in the wire will start to vibrate because of their increase in energy. This causes more collisions between the electrons and the atoms as the atoms are moving into the path of the electrons. This increase in collisions means that there will be an increase in resistance.
2. Material: The type of material will affect the amount of free electrons, which are able to flow through the wire. The number of electrons depends on the amount of electrons in the outer energy shell of the atoms, so if there are more or larger atoms then there must be more electrons available. If the material has a high number of atoms there will be high number of electrons
causing a lower resistance because of the increase in the number of electrons. Also if the atoms in the material are closely packed then the electrons will have more frequent collisions and the resistance will increase.
3. Wire length: If the length of the wire is increased then the resistance will also increase as the electrons will have a longer distance to travel and so more collisions will occur. Due to this the length increase should be proportional to the resistance increase.
4. Wire width: If the wires width is increased the resistance will decrease. This is because of the increase in the space for the electrons to travel through. Due to this increased space between the atoms there should be less collisions.
Results
After collecting the two sets of results I placed them into tables.
The tables are shown on the opposite page.
The first table is only of the results received from the experiment, while the second table is of the same first table except with the resistance added to it.
Resistance table:
Resistance Graph:
These tables below are the tables showing my second set of results and resistance.
Resistance Table:
Resistance Graph:
Because these graphs were not accurate enough to use to draw up a conclusion we had to use the two sets of resistances we had and use the averages of the two of them.
Resistance table:
Resistance Graph:
Evaluation
From my graph I can see that my results that I collected are very reliable. I know this because my graph does not show any individual anomalous results. I can see on the graph that none of the results plotted are anomalous because all the points lie along the same straight line.
When I was measuring the lengths of the Nichrome wire, my measurements might have been slightly inaccurate as the rulers used might not have been exact, and it was difficult to get an accurate reading of length by eye, as the wire was not completely straight. It may also have been of different thickness throughout the length. This would have contributed as a slight error in my results. As this factor probably only made a slight difference, it did not affect my results.
The crocodile clips and the connecting leads could have affected the fairness of the experiment. They are a different type of metal from the Nichrome wire and may have different properties and therefore different resistance. Therefore the resistance of the Nichrome wire showed up on the calculation of my resistance was slightly off. To solve this problem, I would have found out the resistance of the connecting leads and crocodile clips before each experiment and minus it from the overall resistance of the Nichrome wire plus the connecting leads plus the crocodile clips.
To make my experiment possibly more accurate I could have got 3 sets of results and found an average but this would be too time consuming.
I could also have used an ohmmeter to measure the resistance more accurately.
I don’t think I could really improve on the way the experiment was done because my results were very accurate, as I had no anomalous results.
I also found that the experiment was quite easy to set up, as it was simple and uncomplicated.
Further experiments I could do related to the resistance in a wire, would be to see whether the following factors would make a difference in the resistance of a wire.
Wire width:
I think that if the wire width is increased the resistance will decrease. This is because of the increase in the space for the electrons to travel through. Due to this increased space between the atoms there should be less collisions.
Temperature:
I think that if the wire is heated up the atoms in the wire will start to vibrate because of their increase in energy. This causes more collisions between the electrons and the atoms as the atoms are moving into the path of the electrons. This increase in collisions means that there will be an increase in resistance.
Material:
I think that the type of material of the wire will affect the amount of free electrons, which are able to flow through that wire. This is because the number of electrons depends on the amount of electrons in the outer energy shell of the atoms, so if there are more or larger atoms then there must be more electrons available. If the material has a high number of atoms there will be high numbers of electrons causing a lower resistance because of the increase in the number of electrons. Also if the atoms in the material are closely packed then the electrons will have more frequent collisions and the resistance will increase.
Instead of connecting the voltmeter to the main circuit I would connect it to the wire, which is being tested. I would do this so that the voltmeter is measuring the voltage of just the wire being tested and not the wires of the main circuit as well.
To also improve on my results I would use a digital voltmeter instead of an analogue meter. I would do this because a digital voltmeter is a lot more accurate than an analogue because if the needle in the analogue voltmeter is bent then the readings given off will be false whereas a digital voltmeter does not rely on a needle or any other manual movements.
The next modification I would make would be to use pointers instead of crocodile clips; I would do this because pointers would be more accurate. The pointers would be more accurate because the tips have a much smaller area than the crocodile clips giving a more accurate measurement of the length of wire.
As well as making these modifications I would also improve my Investigation by testing the same wire but different widths of that wire. I would do this to expand on my Investigation.
From the graph on the previous page I can see that the resistance of the wire is proportional to the length of the wire. I know this because the Line of Best Fit is a straight line showing that if the length of the wire is increased then the resistance of the wire will also increase.
Conclusion
In my prediction I said that:
If the length increases than the resistance will also increase in proportion to the length.
From my graph I have shown that my prediction was correct, as the Line of Best Fit is a straight line proving that the resistance of the wire is proportional to the length of the wire.
The length of the wire affects the resistance of the wire because the number of atoms in the wire increases or decreases as the length of the wire increases or decreases in proportion.
By Scharlie Tamar Anthea Robinson
Candidate Number: 8122
14343
