As the length of wire increases the resistance will increase because electrons will have to travel further and because there will be more nuclei particles in the wire, which the electrons will bump and collide into, slowing the flow of electrons down.
Short Wire:-
From this diagram you can see there are fewer nuclei so they electrons will collide with them less.
Long Wire:-
From this diagram you can see there is a greater number of nuclei particles in the wire, therefore the electrons will collide more and will be slowed down, so resistance will increase.
Fair test
The experiment will be carried out twice to get reliable results because there may some anomalous results, also to make it a fair test the wire will be cooled down after each interval as temperature can affect results and also the thickness of the wire will be the same for both sets of experiment. Also the power supply will be kept the same at 4.5 volts.
Method
Below is a circuit diagram for the experiment, it contains batteries, crocodile clips, ammeter, voltmeter and Nichrome wire.
The ammeter will be used to measure amps and the voltmeter will be used to measure volts from these readings graphs will be produced, then from the graph points will be taken to work out resistance. The following equation will be used to work out the resistance of the wire.
R=V Resistance (Ohms) = Volts (V)
I Amps (A)
After working out resistance a further graph will be produced to show the results.
Apparatus List
Prediction
The longer the length of the wire the higher the resistance because electrons will collide a greater number of times as there are more nuclei particles as the length of the wire increases, as I explained in the introduction. Also the resistance in the wire will be directly proportional to the length of the wire as Ohm’s Law states ‘that the electrical current flowing through a conductor is directly proportional to the potential difference between its ends, as long as the temperature stays the constant’.
Result Tables
1st set of results
2nd set of results
Resistance
1st set of results:
5cm 1V/1A = 1 Ω
10cm 1V/0.48A = 2.1 Ω
15cm 1V/0.32A = 3.1 Ω
20cm 1V/0.24A = 4.2 Ω
25cm 1V/0.18A = 5.6 Ω
2nd Set of results:
5cm 1V/1A = 1 Ω
10cm 1V/0.0.5A = 2 Ω
15cm 1V/0.34A = 2.94 Ω
20cm 1V/0.24A = 4.2 Ω
25cm 1V/0.19A = 5.26 Ω
Conclusion
In this experiment it can be concluded that the longer the wire, the resistance in the wire increases which agrees with prediction at the start. This is because as they wire gets longer the electrons have to travel further and there will be more nuclei particles in the wire getting it the way of the flowing electrons slowing it down, thus the resistance in the wire increasing.
Short wire: Long wire:
Also the resistance in the wire is directly proportional to the length which agrees with Ohm’s Law mentioned in the prediction. This is because as the wire length doubles so does the amount of nuclei particles, so the flow of electrons will decrease in an equal amount.
Using the line of best fit one can conclude that as the length of the wire increased so did the resistance in the wire. This can be seen from the graph when the wire is 10cm the resistance is 2 Ω, then when the length of the wire is increased to 15cm so does the resistance to 3 Ω. Also from the graph it can be seen that the relationship of length of wire and resistance was directly proportional, hence as the length doubled so did the resistance, this agrees with the prediction I made at the start. On the graph it show when the length of wire was 10cm the resistance was 2 Ω and when the length was 20cm the resistance was 4 Ω. So as the length doubled from 10cm to 20cm the resistance doubled from 2 Ω to 4 Ω.
Collisions can occur between particles in constant random motion, therefore if there are more particles it is more likely to be more collisions. Thus as electrons pass through a longer piece of wire there are more particles which they will collide with making it more difficult for the electrons to move, the more difficult it is for the electrons to move the higher the resistance.
Evaluation
The experiment carried out could be improved so the results are more accurate. Firstly it could be improved by data logging equipment so when one takes readings for volts and amps it would give accurate readings. Also the wire heats up because the current causes friction with the particles in the wire, making the wire heat up which in turn makes the nuclei particles vibrate and move more, impeding the movement of electrons. This causes inaccuracy in the results. So to improve the experiment the wire needs to be at a constant temperature which could be done by putting the wire into a water bath containing distilled water. Distilled water has to be used as it does not conduct electricity because it has no free moving electrons.
There were some anomalous results in the graph showing resistance against length of wire. The graph shows when the wire is 25cm the resistance is 5.6 Ω, this doesn’t fit the pattern of the other results, it should have been 5 Ω. This happened probably because the wire overheated as I mentioned above. So to prevent this happening next time I will keep the temperature of the wire constant by keeping it in a water bath.
The evidence gathered can’t be said to be extremely reliable because other measure could have been taken to make results more accurate and reliable which I mentioned above. However there is sufficient evidence to support the conclusion as the evidence clearly shows as the wire length increases so does the resistance in the wire and also it shows that it is directly proportional. In spite of this there was an anomaly, which I mention earlier which did not fit the pattern and trend of the other results.
As the electrons in an electric current move around a circuit, they collide with nuclei in the wires they are passing through. Atoms of different elements impede the electrons by different amounts. The wire which was used in this experiment is nichrome; electrons find it more difficult to pass through nichrome unlike copper wire which electrons can pass through very easily. So if I carried out any further work to provide additional relevant information I would do the experiment again using different types of wire like copper and aluminium. I would do the experiment exactly the same but replacing the nicrome wire with a different type of wire. I would expect to find there is a different amount of resistance in different wires. This is because different wires have different amounts of particles in them, so a wire with few particles will have very little resistance, as the electrons passing through the wire will not be blocked as much, then they would if they were in a wire with lots of particles inside which will impede the flowing electrons in the electric current moving through the wire.
