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I am stuck at this:(Please solve!​

Answer»

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


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