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# Could you please tell me how to do this.. Watch

1. A coil is made from insulated wire of cross-sectional area 8.4*10^-7 (metres squared)At room temperature,the material of the wire has resistivity 4.9*10^-7. The coil consists of 20 turns and has a mean radius of 2.8cm

show that the total length of the wire is 3.5m
2. (Original post by TheGeneral95)
A coil is made from insulated wire of cross-sectional area 8.4*10^-7 (metres squared)At room temperature,the material of the wire has resistivity 4.9*10^-7. The coil consists of 20 turns and has a mean radius of 2.8cm

show that the total length of the wire is 3.5m
Forgive me if I'm wrong - but assuming the coil is tight you can work out the length of a single coil using and multiplying by 20.
It comes out as roughly 3.5m. It appears that there is not enough info to complete this question using the resistivity.
3. Indeed.
It would be useful if we had the complete question.
I suspect there is more after this part asking to find its resistance or something similar.
4. Yes it asks after that to work out the resistance of the coil.
5. (Original post by TheGeneral95)
Yes it asks after that to work out the resistance of the coil.
So what's the problem?

You now have all the information you need to calculate the resistance:

R = (rho*L)/A

Plug the numbers in and bingo, you have the answer.

What did you get?
6. Found out how to do it.

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Updated: April 12, 2013
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