Question

the resistance (r) in a wire increases when the length of the wire (l) increases. write the correct equation for this scenario, and solve for when the length is 1.

Answer 1

Hello,

This is the law of Pouillet.


`r=\rho* (L)/(S)\\ if \ L=1\ then\ \boxed{r= (\rho)/(S) }`

Answer 2

`r=(\rho)/(A)`

Explanation:

Given,

Resistance (r) in a wire increases when the length of the wire (l) increases,

That is, r is proportional to l

`r\propto l`

Also, we know that Resistance is inversely proportional to the cross sectional area, A,

That is,

`r\propto (1)/(A)`

By combining,

`r\propto (l)/(A)`

`r=\rho (l)/(A)`

Where,
`\rho` is the resistivity constant.

Given, l = 1 unit,

Hence, the required formula would be,

`r=(\rho)/(A)`