Resistivity 3983

What was the length of an iron wire with an area of 3cm² if its resistance was 15 ohms? Iron (Fe) resistivity is 0.0996 x 10 at -6 Ohm/meter.

Correct answer:

l =  45181 m

Step-by-step explanation:

$$\begin{gathered} S=3{\text{cm}}^2\to {\text{m}}^2=3:10000{\text{m}}^2=0.0003{\text{m}}^2 \\ R=15\Omega \\ \rho =0.0996\cdot 10^{-6}\doteq 9.96\cdot 10^{-8}\Omega \text{m} \\ R=\rho \frac{l}{S} \\ l=R\cdot S/\rho =15\cdot 0.0003/9.96\cdot 10^{-8}=45181\text{m} \end{gathered}$$

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