Investigate the factors which affect the resistance of a wire.

Diagram

Preliminary Work

I have done preliminary work to see if the apparatus and the way I did the experiment worked. It will also enable me to make changes so make it a better and more accurate investigation. I will also be able to compare my results with my actual experiment results.

Diagram

Method

• First I will collect all the equipment and set up the circuit. Like the diagram above.
• I will then collect a meter ruler so that I can measure lengths of wire easily.
• Then I will record results at 20cm, 40cm, 60cm, 80cm and 100cm.

Fair Test

To ensure that the investigation is carried out in a fair way and that the results will be accurate and reliable a number of things must be followed. The only variable in the test will be the length of the wire. The wire must be pulled tight against the ruler and taped in place to ensure the length is accurately measured. The same circuit and battery must be used throughout as different batteries may have different voltages if they are old.

Preliminary Results

Conclusion

I will be able to compare these results with my actual results and this will help me see if they are accurate or not.

Actual Work

Diagram

Equipment

Equipment Used:

• Voltmeter
• Ammeter
• Wires
• Crocodile Clips
• Meter Ruler

Method

• First I collected all the equipment I needed and set it up as in the diagram. (See Preliminary Work)
• I then measured 10cm on the ruler and took a recording for Voltage and current. With these 2 recordings I could work out Resistance. (Voltage/Current = Resistance)
• I then repeated this for measurements 20cm, 30cm, 40cm, 50cm, 60cm, 70cm, 80cm, 90cm and 100cm.

Results

V = Voltage.

I = Current.

Ω = Resistance.

Analysis

I think my graph results show that as the length of the wire increases so does the resistance. I know this because the line I have drawn is directly proportional. I think my results are correct because:

• Doubling the length of the wire doubles the number of resisting ions therefore it takes twice as long for the charge to pass through it.
• As the length of the wire increases then so does the number of free electrons. This mean there will be more collisions of free electrons.

My graph results support my prediction.

Evaluation

I think that my results are accurate and reliable because they have enabled me to draw a line of best-fit graph. The graph shows a pattern between 10cm and 100cm and I was able to make a simple conclusion.

My results are quite reliable because I made 3 measurements of current and voltage for each length and used the average values to calculate Resistance. Even with that I still had two anomalous results at lengths 70cm and 80cm.

The experiment I did was successful but I did have some difficulties doing it. If I could redo the experiment I would:

• Make sure that the wire is always taut. If the wire isn’t taut the lengths I measure could be inaccurate and my results wouldn’t be reliable.
• I would make sure that when I used crocodile clips they didn’t scrape the wire because this may affect the thickness of the wire and it would make my results unreliable.
• Make sure that the batteries I use are not old or different as they may have different voltages from each other. This would again make my results unreliable and inaccurate.