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# Resistance - My aim in this piece of investigative work is to take one aspect of a material and see how varying it affects the resistance of the piece of material.

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Introduction

PLAN: My aim in this piece of investigative work is to take one aspect of a material and see how varying it affects the resistance of the piece of material. Theory: A current is the flow of charge (electrons) around a circuit. The potential difference is the push that makes the electrons go round the circuit. Resistance tries to stop the electrons going around the circuit. There are many free electrons in a piece of metal. There are free electrons because the electrons in the outer shells become free or delocalised due to the low attraction between it and the nucleus. When a charge is applied to the piece of metal the free electrons try to get to the positive side of the metal because they are already negatively charged and opposites attract. When the electrons try to travel through, the atoms of the metal get in the way. As the electrons head down they bounce into lots of atoms. This is resistance. Variables: There are overall 4 things I could vary which would affect the amount of resistance. They are.... 1. Diameter: Is very hard to measure. 2. Temperature: It is very hard to keep the temperature constant in this experiment. It would be hard to get continuous results when varying the temperature because not only is it hard to change the temperature it is very hard to measure. ...read more.

Middle

Temperature effect resistance because if it is hotter the vibrations of the atoms increase. This makes it harder for the free electrons to travel through the wire. Again, in my preliminary results I found that constantan is a good metal to use because the resistance doesn't change depending on what temperature it is. I tried copper but it was not nearly as good. I then found out that copper has a temperature coefficient of 43.00 where as constantan has one of 30.00. So my experiment will... 1. Set up equipment. 2. On the 1m board underneath the wire, mark out intervals at every 10 cm 3. Connect the crocodile clips from the voltmeter to the first 10 cm point. 4. Turn the power pack firstly to 4 volts. 5. Record results 6. Do this for every 10 cm 7. After you have done the length of the wire, change the voltage on the power pack to 2 amps and record the results again. I will then work out the resistance of each measurement using the equation in my theory. Prediction: My prediction is that the longer the length the more resistance. I have many reasons and theory's to back up this prediction. The longer the piece of wire the more atoms the electrons have to be pushed through. ...read more.

Conclusion

An average is much more accurate than 1 single measurement. I can tell my experiment was a success because my graph made a straight line which I s what I predicted due to Resistivity. I think my results gained from this experiment are enough to prove my hypothesis. Because I only went up to 1m this was a slight limitation. It would have been better to use bigger lengths and got more results to be more thorough. Again I think my results are conclusive because they follow a pattern and I can relate them back to my theory's of resistance and Resistivity. There are some slight ways I could change my experiment to make it more accurate. I could take three reading rather than two just for the extra security that my results are completely accurate. I could use longer lengths of wire for a larger range of results. To extend me experiment I could take a different variable of the ones I discussed in my plan. Of course if I did this I would have to keep length the same. I could look into Resistivity and temperature coefficient in more detail to deepen my thought and understanding in the subject. I have thoroughly enjoyed this experiment and have learnt a lot from it. It has been very beneficial. Lucy Smith Resistance 07/05/2007 Mr Pompfrett GCSE Physics Coursework ...read more.

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