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Resistance, ohms

  • Thread starter dymand68
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  • #1
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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



The Attempt at a Solution

unable to attempt, I know that when it is cut in half R=34 ohms
 

Answers and Replies

  • #2
Doc Al
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I know that when it is cut in half R=34 ohms
OK. More generally, how does resistance depend on length and cross-sectional area?
 
  • #3
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inverse square rule?
 
  • #5
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the correct answer is 17 ohms...double width, 1/2 length =1/4 resistance?
 
  • #6
Doc Al
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44,877
1,129
the correct answer is 17 ohms...double width, 1/2 length =1/4 resistance?
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).
 

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