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To investigate how the electrical resistance of a wire changes in relationship to its length.

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Introduction

Amandeep S. Gill Science Resistance of a Wire Aim: To investigate how the electrical resistance of a wire changes in relationship to its length. Before I write about my experiment, I will recap Ohms law as I know that this has an important role in the latter stages of my experiment. I will fully mention and explain this in the Analysis and the Prediction Ohm's Law, It states that the current flowing through a component is proportional to the potential difference between its ends, providing temperature is constant Word Formula : Current = Voltage / Resistance Symbol Formula : I = V / R Equipment Used, The following is a list of the equipment that I used during this experiment and the reasons and purposes of each object: * Nichrome Wire - I used this type of wire in my experiment because it has a big resistance compared to other metals. This wire was secured on top of the ruler so that the resistance could be measured accurately. * Power- Pack - This gives the current to the wire which is connected to the circuit. * Amp- Meter - This device reads the amount of amps which is occurring from the experiment. ...read more.

Middle

Dry Hands - It is essential when dealing with electricity I keep and stick to the correct precautions, and keeping my hands dry is common sense when dealing with electricity. Reliability, To keep this experiment as accurate as possible I need to make sure, firstly, that the length of the wire is measured precisely from the inside edge of the crocodile clips, making sure that the wire is straight when I do this. I must also make sure that the wire is straight when we conduct the experiment. If it is not, short circuits may occur and bends and kinks in the wire may effect the resistance. The reading that I take of the voltage should be done fairly promptly after the circuit is connected. This is because as soon as a current is put through the wire it will get hotter and I want to test it when heat is effecting it the least, i.e. at the beginning. Results, The tables below are showing the three repeated results which I carried out during this experiment: Experiment 1, Length Voltage Current Resistance 10 4.5 6.58 0.68 20 4.5 4.55 0.99 30 4.5 3.43 1.31 40 4.5 2.85 1.58 50 4.5 2.40 1.88 60 4.5 2.07 2.17 70 4.5 1.80 2.50 80 4.5 1.61 ...read more.

Conclusion

Most errors in our experiment were encountered in the measuring of the wire. This is because it simply was not very practical to hold a piece of wire straight, whilst holding it next to a ruler and then trying to accurately fix crocodile clips to the right part on the wire. Also I do not feel that the crocodile clips were always fixed securely to the wire with a good connection. This also meant that they were easy to move about on the wire changing the length of it. Errors rarely occurred in the setting of the current and the reading of the voltage. It was just in the preparation area that they did occur. Another example of this is the wire was never totally straight when we started the experiment, which may also, as said earlier on, effect the resistance of it. I do not think that doing any more results in our experiment would have made it any more accurate. I feel that the only way to make it more accurate would be to use a different method - perhaps were we had a bar that did not bend in place of the wire. We could even use a rheostat in place of the wire, because it is essentially a long coiled wire that is connected at different lengths to change the resistance of the circuit ...read more.

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