Name: Luke Smallwood
An Investigation into Finding the Different Values of Resistance with Different Lengths of Wire
In this experiment I intend to find out what happens to the resistance of a wire, when we increase or decrease the length of the wire.
- Length of tested wire.
- Ammeter reading and voltmeter reading.
- The tested wire,
- Power supply,
- The leads connecting the components together,
- The ammeter and voltmeter.
- The resistor
I predict that in this experiment the results will show us that the longer the wire the more resistance the wire will have, and that if the wire doubles in length, the resistance will double. I also predict that the results graph will look similar to the one below:
I have predicted this outcome for my experiment due to the scientific knowledge that I have obtained. I predicted that the longer the wire the more resistance there would be, because when a voltage is applied across the wire, it causes the electrons to move creating a flow of current. When an electron collides with atomic nuclei, it looses its energy and this is called resistance.
Therefore the longer the length of wire the more atoms there are for the electrons to collide into so therefore there will be more resistance and so that is why I have predicted that the double the amount of wire, the double amount of resistance there will be, as there will be double the amount of atoms, so therefore there will be double the amount of resistance.
In this experiment there are few but important safety issues to consider and are the following:
- Not to touch the wire as when current flows through the wire, the wire may become hot.
- Not to touch the electricity.
- Make sure the wire is coated completely in plastic so as to reduce the chances of an electrical shock.
- Do not have any liquid, such as water, when carrying put the experiment, as this will offer a greater chance of any kind of electrical shock.
This is a preview of the whole essay
In order to make my experiment fair I will keep the following factors the same:
- The thickness of the wire constant throughout the experiment as different thickness’ of wire will offers different routes for the current to flow through so will alter the results.
- Use the same wire during the experiment as different wires, of even the same thickness, will offer different resistance, due to different amount of atoms within the wire and may offer different resistance between two wires the same lengths because they could have different atom constellation so will offer different routes for the flow to take.
- Keep the length of tested wire e.g. 20cm, 40cm, constant thought out the repeated experiments.
- Use the same voltage throughout the experiment, as a different voltage will give a different current.
- Repeat the experiment three times.
- Keep all the apparatus the same throughout the duration of the experiment.
- After carrying out an experiment, wait for the wire to cool down as during the previous experiment the wire may have heated up and as the temperature of the wire increases the atoms in the wire move faster. This will then increases the chance that the electrons will collide with the atoms and loose their energy as they move along the wire so there will be more resistance.
For this experiment I will need the following pieces of apparatus:
- 1m of wire, of thickness 0.45mm to be the tested piece of wire,
- 6v power supply for the current,
- Ammeter to record the current through the wire,
- Voltmeter to record the voltage through the wire,
- Resister of 47 Ω to protect the ammeter,
- Leads to connect components,
- 1m rule to measure out the different lengths on the same 1m piece of wire,
- Crocodile clips to connect the tested wire to the circuit.
Here is a diagram of how the apparatus will be set up:
- Set up the apparatus as shown in the circuit diagram above.
- Set the crocodile clips so they cover 20cm of the tested wire and then record the result shown on the ammeter and voltmeter.
- Then record the current and voltage for 40cm, 60cm, 80cm and 100cm, but in between each experiment wait for the wire to have a chance of cooling down.
- Repeat the experiment two times.
- Calculate the resistance for each length of wire for each experiment by using R=V/I.
I carried out a preliminary experiment because I wanted to investigate which voltage would give suitable readings for my experiment.
I did this investigation by testing three different voltages over 20cm of wire. I tested 9v, 6v and 3v and recorded the current and voltage.
The results were:
I have not needed to modify my experiment because my original voltage was 6V and my preliminary experiment shows that 6V is a good voltage to be used in this experiment so I will not need to change any variable when carrying out the experiment.
My results show that the longer the wire the more resistance there will be. The graph shows that there is a linear (straight line) relationship between the length of the wire and resistance.
This happened because the electrons collided with the electrons and the longer the wire the more chance there is of the electrons colliding with the atoms so therefore is more resistance.
Comparison with my Prediction
My prediction was that:
Longer the wire the more resistance the wire will have, and that if the wire doubles in length, the resistance will double.
When comparing the results I have obtained, the conclusion I have come to and with the prediction I made, my conclusion and prediction partially agree when I predicted that the longer the wire, the greater the resistance will be, because my graph showed that there was a linear relationship between length of wire and resistance.
My conclusion and prediction did not agree when I predicted, that if the wire doubles in length, the resistance will double, because at 20cm the resistance was 0.7Ω and the resistance at 40cm should have been 1.4Ω according to my prediction, but the experiment showed that it was 1.3Ω, but my prediction would have been correct if read: that if the wire doubles in length, the resistance will roughly double, as 1.3Ω is very near double 0.7Ω and this also occurs in the comparison between 40cm and 80cm. At 40cm the resistance was 1.3Ω and at 80cm the resistance was 2.4Ω, again, nearly double the resistance
Quality of my Results
The results I obtained are of a good quality for the following reasons.
- There are no anomalous results that don’t follow the trend,
- The first, second and third experiments results are similar,
- The points of the graph form a good straight line.
To improve my experiment I could have done the following:
- Given the wire a longer period of time to cool down,
- Accurately measured out the lengths of wire,
- Used more accurate ammeters and voltmeters, as during some experiments the meters kept on moving from one value to another e.g. 1.8 volts to 1.9 volts.
The sources of error in this experiment are as follows:
- The voltmeter readings had to be rounded to the highest figure as the voltmeter on some occasions kept on moving from one value of voltage, to another.
To extend my investigation I could investigate the different values of resistance with different values of voltage. This is how I would go about doing that.
My aim for this experiment would be to investigate what levels of voltage would affect the levels of resistance.
- Use and set up the apparatus as the same as in the experiment, An Investigation into Finding the Different Values of Resistance with Different Lengths of Wire, but using only a set length of wire to be tested on e.g. 60cm, 80cm, and 100cm.
- Using the voltages 3v, 6v, 9v and 12v, measure the current and voltage over the selected length of wire.
- Repeat this experiment three times.
- Calculate the resistance for each voltage for each experiment by using R=V/I.
I predict that in this experiment, that the higher the voltage, the higher the resistance will be and that the double the voltage, the double the resistance will be, because the more voltage behind the current, offers more chance of the electrons colliding with the atoms in the wire, so therefore offers more chance of resistance.