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# Re-submitting now that I am a member -- Really Stumped

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The resistance, R (in ohms) of a wire varies directly with the length, L (in cm) of the wire, and inversely with the cross-sectional area, A (in cm^2). A 500 cm piece of wire with a radius of 0.2cm has a resistance of 0.025 ohm. Find an equation that relates these variables in the form of $$R = \frac {\square\cdot \pi\cdot L}{\square}$$

BillHicks1207  Apr 5, 2017
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The resistance, R (in ohms) of a wire varies directly with the length, L (in cm) of the wire, and inversely with the cross-sectional area, A (in cm^2). A 500 cm piece of wire with a radius of 0.2cm has a resistance of 0.025 ohm. Find an equation that relates these variables in the form of  $$R=\frac{\Box \cdot \pi \dot\ L}{\Box}$$

$$R=\rho\times \frac{L}{A}$$

$$R[\Omega]=\rho[\frac{\Omega \cdot mm^2}{m}]\times \frac{L[m]}{\pi\cdot r^2[mm^2]}$$

example

$$R=0,025\Omega$$

$$r=2 mm$$

$$L=0.5 m$$

$$\rho=\frac{A\cdot R}{L}=\frac{r^2\pi\cdot R}{L}=\frac{2^2mm^2\cdot \pi \cdot 0.025\Omega}{0.5m}\color{blue}=0.62832\frac{\Omega \cdot mm^2}{m}$$    [ stainless steel ]

!

asinus  Apr 5, 2017