Question

A silver wire is 0.04 mm it is used to make a resistance of 1ohm if the resistivity of silver is 1.6*10^-8 then calculate the length of the wire needed

Answer 1

`l=7.853\ cm\approx0.079\ m`

Step-by-step explanation:

Given:

• thickness of silver wire,
  `d=0.04\ mm=4* 10^(-5)\ m`

• resistivity of silver,
  `\rho=1.6* 10^(-8)\ \Omega.m`

• resistance,
  `R=1\ \Omega`

As we know, resistance:

`R=\rho (l)/(a)`

`1=1.6* 10^(-8)* (l)/(\pi.(d^2)/(4) )`

`(1)/(1.6) * 10^8* \pi* ((4* 10^(-5))^2)/(4) =l`

`l=7.853\ cm\approx0.079\ m`