i] List the differences between electrical resistance and resistivity of conductor.
ii] A copper wire of resistivity `1.63xx10^(-8)Omega-m` has cross section area of `10.3xx10^(-4)cm^(2)`. Calculate the length of the wire required to make a `20Omega` coil.

Explanation

i]
ii] `rho=1.63xx10^(-8)`Ohm-m
`A=10.3xx10^(-4)cm^(2)=10.3m^(2)`
R = 20 Ohm
`R=rhoL/A`
then, `L=(20xx10.3)/(1.63xx10^(-8))=126.4m`
`L=1.264xx10^(10)`m
[cross section is very large...that is why the resistance is too small.]
If the area A = `10.3xx10^(-4)cm^(2)=10.3xx10^(-8)m^(2)`
then `L=(20xx10.3xx10^(-8))/(1.63xx10^(-8))=126.4m`