[tex]\tt Se~da:\\ \\
\rho_{1}=28,2n\Omega\times m=2,82 \times 10^{-8}\Omega\times m\\ \\
l_{1}=2,5m\\ \\
a=1cm=0,01m\\ \\
b=5cm=0,05m\\ \\
\rho_{2}=98n\Omega\times m=9,8 \times 10^{-8}\Omega\times m\\ \\
d=15mm=0,015m\\ \\
R_{1}=R_{2}\\ \\
a)R_{1}=?\Omega\\ \\
b)l_{2}=?m\\ \\ \\[/tex]
[tex]\tt Formule:\\ \\
a)R_{1}=\rho_{1} \times \frac{l_{1}}{S_{1}}\\ \\
R_{1}=\rho_{1} \times \frac{l_{1}}{a\times b}\\ \\ \\
b)R_{2}=R_{1}\\ \\
R_{1}=\rho_{2}\times\frac{l_{2}}{S_{2}}\\ \\ \\
S_{2}=\pi\times R^{2} \\ \\
S_{2}=\pi\times\frac{D^{2}}{4}\\ \\ \\
R_{1}=\rho_{2}\times\frac{l_{2}}{\pi\times\frac{D^{2}}{4}}\\ \\
R_{1}=\rho_{2}\times\frac{4 \times l_{2}}{\pi\times D^{2}}\\ \\
l_{2}=\frac{R_{1}\times \pi \times D^{2}}{4\times\rho_{2}}\\ \\ \\[/tex]
[tex]\tt Calcule: \\ \\
a)R_{1}=2,82 \times 10^{-8} \times \frac{2,5}{0,01\times 0,05}=14100\times 10^{-8} \Omega\\ \\ \\
b)l_{2}=\frac{14100\times 10^{-8}\times 3,14 \times 0,015^{2}}{4\times 9,8 \times 10^{-8}}\approx 0,255m\\ \\[/tex]
