119,613 views
45 votes
45 votes
Determine the resistance, in milliOhms, of a metal rod 2.39 m long, 0.47cm diameter and composed of aluminum of resistivity 2.8 x 10-8 Ωm .

User Anis Abboud
by
2.4k points

1 Answer

15 votes
15 votes

0.965 mililΩ

Step-by-step explanation

The resistance of a metal rod depends on resistivy, length and temperature, it can fe found usign the formula


\begin{gathered} R=\rho(L)/(A) \\ where\rho\text{ is} \\ L\text{ is the length } \\ A\text{ is the seccion of area} \end{gathered}

sp

Step 1

a) let


\begin{gathered} \rho=2.8*10^(-8)m\text{ ^^^^2126} \\ L=2.39\text{ m} \\ d=0.4\text{ cm=0.4 cm\lparen}\frac{1m}{100\text{ cm}}\text{\rparen=0.0047 m} \end{gathered}

b) find the transversal area (A)

use the area of a circle


\begin{gathered} A=\pi r^2 \\ replace \\ A=\pi(0.0047\text{ m\rparen}^2 \\ A=6.93*10^(-5)m^2 \end{gathered}

c) now, replace in the formula


\begin{gathered} R=\rho(L)/(A) \\ R=2.8*10^(-8)m\text{ ^^^^2126*}\frac{2.39\text{ m}}{6.93*10^(-5)m^2} \\ R=0.00096565\text{ ^^^^2126} \end{gathered}

finally, to convert into milliOhms, Multiply by 1000


\begin{gathered} R=0.000965365*1000\text{ m^^^^2126} \\ R=0.965\text{ m^^^^2126} \end{gathered}

therefore, the answer is

0.965 miliΩ

I hope this helps you

User Sqwerty
by
2.5k points