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## Homework Statement

A 1 mile long copper wire has a resistance of 68 ohms. What will be its new resistance when doubling it over and using it as "one" wire

## Homework Equations

?R=V/current

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- Thread starter dymand68
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A 1 mile long copper wire has a resistance of 68 ohms. What will be its new resistance when doubling it over and using it as "one" wire

R=V/current

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Doc Al

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OK. More generally, how does resistance depend on length and cross-sectional area?I know that when it is cut in half R=34 ohms

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inverse square rule?

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Doc Al

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No. Read this: http://hyperphysics.phy-astr.gsu.edu/hbase/electric/resis.html#c2"inverse square rule?

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the correct answer is 17 ohms...double width, 1/2 length =1/4 resistance?

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Doc Al

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That's right. As that site explains, the resistance is inversely proportional to the cross-sectional area (which gives one factor 1/2) and directly proportional to the length (which gives a second factor of 1/2).the correct answer is 17 ohms...double width, 1/2 length =1/4 resistance?

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