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# Physics Coursework Dilemma: Resistance watch

1. Hey all,

I'm doing an investigation into resistance, specifically the effect different diameters and lengths of wire has on the resistance of said wire.

I'm a little stuck in my plan. I've actually conducted the investigation, but I've come to explaining my prediction in scientific terms. Any textbooks I have are useless on the subject.

My prediction is thus; the longest, thinnest wire will resist the current by the greatest amount. All's well and good up to there, but then I have to explain why this happens.

I think it has something to do with the wire being thinner, and containing less electrons/less electrons being able to fit through it; but I feel this is not nearly in depth enough.
I also have no idea what the length has to do with the resistance. I've probably forgotten something I've been taught, but I've lost my old book anyway.

Any help on the matter is much appreciated. As detailed as possible would be fantastic. I don't plan to copy and paste, so feel free to quote text books.

Cheers,
Ben
2. (Original post by mAcHiNeHeAd)
My prediction is thus; the shortest, thinnest wire will resist the current by the greatest amount. All's well and good up to there, but then I have to explain why this happens.
what makes you say that?
3. Crikey. I've just re-read my results table, and you're right. I got them mixed up, so I've amended the first post accordingly.

Cheers mate, a real life saver.
4. R =pl/a
5. The reason the resistance is greatest when the wire is long, is due to the fact that the transfer of electrical energy, or rather, the movement of current; is due to electron movement. The electrons take a longer time to move around a long piece of wire, due to the fact that there are more atoms in the space between one end and another, and these slow the transfer of electrical energy.

Furthermore, if the wire has a smaller diameter, the resistance will be increased, due to the fact that there is a smaller surface area through which the electrons can travel. This is similar to altering a pipe diameter and seeing how much water can flow through at once. By making the diameter smaller, the flow rate of electrons through the material is restricted.

I hope that helps you. If you want any other advice, or help, PM me, or reply here... Good luck with the cw.

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