# formula help please



## Dennis Alwon (May 9, 2009)

flyinghigher2011 said:


> can someone please tell me how to work this formula out please.
> 
> Calculate the resistance of a 100m length of copper conductor of cross sectional area 4 mm2 if the resistivity of the copper is 17.4 mm3


I don't understand the last bit of info 17.4 ??? I see two squares then mm3. Resistance is usually ohms or ohms/km


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## flyinghigher2011 (Sep 20, 2012)

Dennis Alwon said:


> I don't understand the last bit of info 17.4 ??? I see two squares then mm3. Resistance is usually ohms or ohms/km


U and the ohms sign then mm3


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## bryanh (Oct 12, 2012)

Resistance of a cable is usually shown as Ω/km so I would expect it to read 17.4 Ω/km so 17.4÷1000 x 100 = 0.40Ω


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## Berlioz (Jan 13, 2012)

R=0.0174*100/4=0.435


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