Question

I am stuck at this:(
Please solve!​

Answer 1

Don't worry at all : )

Resistivity($\rho$)=$1.57 \times 10^{-6}$

Radius=1mm or $\frac{1}{1000}m$

Resistance= 9ohm

• Convert radius into metres
• Calculate the cross section area with $\pi r^2$
• Use formula $R= \frac{\rho l} {A}$

Solution:

Let the Length be L

Area of cross section= $\pi r^2~=> \frac{\pi}{10^6}$

=> after calculation, we get $3.14 \times 10^{-6}$ metre square

Resistance=$R= \frac{\rho l} {A}$

$\mapsto 9= \frac{ 1.57 \times 10^{-6} \times L } {A}$

$\mapsto 9= \frac{ 1.57 \times 10^{-6} \times L } {3.14 \times 10^{-6}} \\\\\mapsto 9= \frac{ 1.57 \times \cancel{10^{-6}} \times L } {3.14 \times \cancel{10^{-6}}}\\\\ \mapsto 9= \frac{1.57 \times L} {3.14} \\\\\mapsto L=\frac{9 \times 3.14}{1.57} \\\\\mapsto L= 18m$

Now it's correct I guess