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.

i] List the differences between electrical resistance and resistivity

1.	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.
Answer» Solution :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`