How does the length of wire affect resistance?

How Does the Length of Wire Affect Resistance?

During this experiment I am going to be studying the resistance of a 28swg Constantine wire. The purpose of this investigation is to see how the length of the Constantine wire affects the resistance of the electrons flowing through the wire.

The aim of this experiment:

To investigate how the electrical resistance of a wire changes in relationship to its length

Resistance

Resistance means the property of anything, which constricts the flow of the electrons. Resistance occurs when the electrons traveling along the wire collide with the atoms of the wire. These collisions slow down the flow of electrons, which causes more resistance. The resistance increases or decreases if there are more or less atoms in the wire. Resistance is a measure of how hard it is to move the electrons through the wire.

Variables that could affect my experiment:

There are many variables that could affect this experiment some of which are:

The temperature of the wire:

If the wire is heated up, the atoms in the wire will start to vibrate more rapidly because of their increase of temperature and energy. This will then cause more collisions between the electrons and the atoms. This is because the atoms in the wire are vibrating more which is causing them to get into the way of the flowing electrons. So because there is an increase in the collision this will mean that there will be an increase in resistance.

The material of the wire:

If the type of material is changed the resistance could change as in a thin wire the atoms are more closely packed together which will increase resistance, so if the material is changed this will increase or decrease the resistance, as it will determine how many free electrons can flow through the wire. If the atoms in the wire are closely packed together the will be more collision where as if they are spread out more there will be fewer collisions, as there is more space in between them and so the resistance will decrease due to the extra space in-between each atom.

The wire length:

As the length of the wire increase so does the atoms in the wire, this will therefore increase the resistance, as there will be more atoms for the flow of elections to pass through. Because of this the atoms and electrons will collide more so this is why the resistance will increase. There will be more collisions, as there will be more wire and atoms for the flow of electrons to travel through, so you would think that if the wire doubles the resistance will double, as there are double the atoms in the wire, ...

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The wire length:

The cross sectional area of the wire:

As the cross sectional area of a wire increases the resistance will decrease, this is because the space for the flow of electrons to travel through has increased, so therefore there is less chance of collisions. So due to this increased space in between the atoms there is less chance of colliding, as not as many atoms will be in the way of the flow of the electrons.

Key Variable:

Out of these 4 variables the one I will be changing will be the length of the wire, we will change the wire by 40cm each time, enabling us to draw up a precise conclusion of how the length of a wire affects resistance.

Hypothesis:

As I already know, the length of the wire affects resistance, so I predict that as the length of the wire increases the resistance will also increase, giving me a positive correlation. This is because there are more atoms for the free electrons to pass through so there will be more collisions therefore increasing the resistance of the wire. So I can say that the resistance is proportional to the length of the wire. Also from my preliminary work I discovered that when doubling or halving the wire length, the resistance also doubles or halves, because of there being twice as many, or half of the atoms to pass through, reducing the amount of collisions.

Safety:

This experiment is not really dangerous but as I will be using electricity I will make sure I don’t have wet hands when handling the equipment and I will not increase the current unless need to as it could make the wire hot and it could burn me.

Fair test:

To keep my experiment fair I will take the following factors into consideration, temperature, the length of the wire, the material the cross sectional area and the amount of current and human errors. I will do my best to ensure that the temperature of the wire and the room will stay the same because if the wire is heated the atoms will vibrate more, which would have an effect on the resistance as the more the atoms vibrate the higher the risk of collisions. I tried to make sure that the wire length was always on the correct length and tried to clip the crocodile clips on to the correct spot of the wire but due to human errors these might not have been the same all the time. I will also try to make sure that the current on the power pack is two and I will turn the power pack off after every reading in order for the wire to not get too hot. I will also make sure that the cross sectional area is the same every time I do the experiment, which is 28 swg.

Equipment list:

Power pack.
2 metres of 28swg Constantine wire.
5 wires.
2 crocodile clips.
Ammeter.
Voltmeter.
Circuit board.
Metre ruler.

Diagram of the experiment:

Method:

Collect all the equipment and check that it works
Set up the circuit correctly, according to the diagrams from the preliminary work with the voltage as 2 and the power pack being on direct current.

Without cutting the wire, measure 40cm from the 2 metres of Constantine and put crocodile clips at either end of the measurement.

Look at the ammeter and record the reading of the current in a table.

Without cutting the wire, measure 80cm from the 2 metres of Constantine and put crocodile clips at either end of the measurement.

Look at the ammeter and record the reading of the current in a table.

Without cutting the wire, measure 120cm from the 2 metres of Constantine and put crocodile clips at either end of the measurement.

Look at the ammeter and record the reading of the current in a table.

Without cutting the wire, measure 160cm from the 2 metres of Constantine and put crocodile clips at either end of the measurement.

Look at the ammeter and record the reading of the current in a table.

Then measure the full length of the 2 metres of the Constantine and put crocodile clips at either end of the measurement.

Look at the ammeter and record the reading of the current in a table.

Then repeat the experiment two more times so you have 3 sets of results all together.

Results table

Conclusion

As the length of wire increased so did the resistance. This supports my prediction. This was as I increase the length of the wire the resistance of the wire will also increase. I thought this because the amount of atoms the free electrons had to pass though was increased. Therefore the longer the wire, the more atoms there will be for the free electrons to pass so therefore there will be more collisions. When looking at my graphs from my results I can see no anonymous points so that’s means that my results were accurate enough to give me a firm conclusion. I can also see from looking at my graphs that they show that as length of wire increase so does resistance which means that’s it has a positive correlation so from this I can tell that the length of wire is proportional to resistance so that my prediction is again correct.

Evaluation

If I could redo this experiment I would only change a few things one of these would be the accuracy in the length. I would try to find a way to make sure when clipping the crocodile clips they are exactly on the length required, without any human errors. I will also make my method fit for he task and try to minimise the heat change of the wire as that would affect my results. I will also repeat the experiment a few more time in order to get a clearer result at the end and figure out how and why the resistance of a wire is proportional to its length in more detail. When repeating the experiment I would make the range of the length we were measuring the wire wider so ill take more readings as that would make my results even more precise. But seeing that I done 5 different ranges my results were precise enough to give me a firm conclusion but if I were to take more readings it would make it even more precise. Because if I hadn’t clear results there could have been many alternatives conclusions that could have been found due to my tables. To also have increase knowledge on resistance I could have repeated the experiment with different wires and different temperatures to get a carer understanding of how the length of wire increases resistance.