2 batteries and cut a length of wire, at least 60 cm long)
- Attach one end of wire to the crocodile clip and using the meter ruler measure 60 cm and clip the second clip at this point on the wire.
- Put the voltage onto 2 volts on the voltmeter.
- Take the reading of the ammeter so the resistance can be found.
- Repeat this method three times for each length of wire so the average resistance can be worked out.
- Repeat this method for every length of wire. We will start with 60 cm and work down to 20 cm.
Variables: These are some variables which I could use for this experiment:
- Length of wire
- Diameter of wire
- Temperature
- Different materials
I have decided to vary the length of wire in my experiment to see how it affects the resistance in the wire.
Safety: This how I will keep the experiment safe:
- I must not touch the wire as it can burn.
- Put a heat proof mat under the wire in case it melts during the experiment.
Preliminary results:
I have decided to do some preliminary work to see if the table below that I have chosen to do is alright, and if my method is correct.
My prediction appears to be correct as I stated above, that the longer the length of wire the higher the resistance. The results in my results table also support my prediction and I will not therefore be changing my original plan as there is no need to do so. I have followed the plan exactly as I have written it down.
Results: This is the results table I am going to use for my final results so far.
Conclusion:
From my results I can see that the longer the wire the greater the resistance becomes, and the shorter the wire the smaller the resistance is.
My graph shows that with every length of wire tested there is a gradual increase in the resistance. This is shown as a diagonal line on my graph. This means that the resistance in the wire obeyed Ohms law (V = I x R). I predicted that a shorter piece of wire would have less resistance because it has less electrons flowing through it. These electrons move using the domino effect.
The domino effect is when the electrons move through the atoms. This means that in a shorter piece of wire there are less atoms for the electrons to flow through, causing less resistance in the current. The opposite of this will happen in a longer piece of wire where there are more atoms for the electrons to pass through. This causes there to be more resistance with a greater area for the atoms to cover.
I also carried out preliminary work which helped me to form this prediction. In the preliminary experiment I tested a couple of lengths of wire and worked out the resistance. After carrying out this preliminary work I found that the longest piece of wire (60 cm) caused the largest resistance in the circuit (2.8 Ω). I also found that the shortest piece of wire (20 cm) had the least resistance (1.1 Ω). By using my knowledge of resistance and my preliminary experiment’s results I predicted that the longest length of wire would have the greatest resistance. A noticeable pattern seen was that the resistance of the wires increased by 0.3 to 0.6 Ω on every occasion during the experiment.
Evaluation:
My prediction was correct. I did find that the shortest length of wire had the least resistance and that the longest piece had the highest reading. My original prediction therefore appears to be accurate. Also my preliminary work backed up my results from my experiment and has given me reliable results. To make sure that the longest wire does have the greater resistance I would like to test longer pieces of wire to see whether the gradual increase that I found in my graph would continue.
To improve the experiment I could use more pieces of wire, e.g. up to 1 metre of wire to see whether it behaves as the other wire lengths did. Also I could increase the wire lengths by 5 cm, not 10 cm as in this experiment. I could test their resistance and get more accurate results of how resistance behaves in various wire lengths. This will provide more results to base a firmer conclusion on.