A 47.6 g sample of a conducting material is all that is available. The resistivity of the material is measured to be 1.30×10-7 Ωm and the density is 7.21 g/cm3. The material is to be shaped into a solid cylindrical wire that has a total resistance of 1.29 Ω. What length is required?

Question

anonymous · Answer

What have you done till now ?

anonymous · Answer

@witthan1 ??

anonymous · Answer

Okay so I have 47.6/7.21 =6.602E-6

anonymous · Answer

then that times (1.29)/1.30E-7

anonymous · Answer

=8.514E-6 but it says its wrong

anonymous · Answer

I have to leave for work pretty soon

anonymous · Answer

Length = Resistance * Cross section area / resistivity

anonymous · Answer

But cross section area = volume/ length
So,
Length = Resistance * (volume/ length) / resistivity

anonymous · Answer

Now solve for length

anonymous · Answer

so 7.21/1.30E-7

anonymous · Answer

I dont understand

anonymous · Answer

Length = Resistance * (volume/ length) / resistivity 
$length = \sqrt{Resistance*volume / resistivity}$
Do you understand how this formula obtained?