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# An experiment to investigate the effects of different lengths of wire on resistance

Extracts from this document...

Introduction

Neha Poshakwale

An experiment to investigate the effects of different

lengths of wire on resistance

Aim

The aim of our experiment is to investigate how increasing the length of a wire affects the resistance in the wire.

Prediction

The collisions between electrons and atoms in a wire cause resistance. Therefore if I double the length of an identical piece of wire then the resistance should double as well. My point is explained in figure 1 by using an example experiment.

Therefore we realise that resistance is directly proportional to the length of wire, this means that as the length doubles/increases the resistance doubles/increases as well. So I would expect a straight-line graph from my results if they are accurate, like the one shown below in figure 2:

In figure 3 we can see the amount of resistance in a wire:

Ohm's law is a mathematical formula that expresses the relationship between the electromotive force, electric current, and resistance in a circuit.  This relationship was discovered by the German physicist George Ohm, and was published in 1827.  When applied to a direct-current circuit, Ohm's law states that the electromotive force (V), measured in volts, equals the current (I) in amperes multiplied by the resistance (R) in ohms: V = IR.

Resistance is calculated by using the equation below.

Middle

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1. Then we would record our results in a table and work out the amount of average resistance (average voltage/average current).

To ensure that this experiment is going to be a fair test all the variables except for the length of the wire must be kept the same throughout the experiments. Variables that should not altered include:

• Temperature
• Material
• Cross-sectional area
• Type of wire
• The amount of voltage from the Powerpack.

The effect of these variables is explained at the beginning of my coursework.

Precautions/Safety

I would carry out the experiment keeping in mind the following rules:

• Keep the current at a safe voltage because it could become hot.
• Keep our stools well tucked under our chairs to avoid accidents.
• To use appropriate lengths of wire so that it will not start to get hot or burn.
• To keep the experiment away from the tables edge so it would not fall.
• Only turn the Powerpack on when everything is in place.
• When changing the length of wire to turn off the Powerpack.

Conclusion

Overall I thought that my experiment was very successful, however if I had more time and money then my experiment would have been more accurate and reliable.

If I had more time then I would have repeated the experiment several times (for examples, seven times) this would make my results more reliable. Plus, I could take a wider range of lengths (readings) say may be a 100 or 90 reading instead of just 45 (which is how many readings I took). Another thing that I could do was to investigate other variables, which affect resistance (for example temperature, cross-sectional area and material). Also I could take time to read/research published experiments and use other people's results.

If I had more money I would buy more specialist equipment to take reading (to 5 d.p.) this would make my experiment more accurate. I could also perform the experiment in a special lab where I can alter the temperature, to suite my experiment. I could also purchase a laptop, which could take down the readings and draw the graph for me; this also might make my experiment more accurate.

All my suggestions would make my results more reliable and accurate.

Bibliography

Here are the books/websites I referred to in providing evidence and scientific knowledge to support parts of my coursework:

• Physics 4 U by Keith Johnson p259
• Complete Physics by Stephen Pople
• www.homeworkhigh.com
• www.learn.co.uk
• www.schoolsnet.co.uk
• www.yahoo.com

This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism section.

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