Question

A wire of copper has a resistance of 10ohm. How much long wire do you need if area of cross section of wire is 0.25mm^2. (Resistivity of copper is 1.62×10^-8 ohm meter)​

Answer 1

R=(resistivity*length)/area of cross sec

R=rho*l/A

10=1.62*10^-8*l/0.25*10^-6

10^-6 due to reason of conversion of mm^2 into m^2

l=10*0.25*10^-6/1.62*10^-8

l=10*0.25*10^2/1.62

l=250/1.62

l=154.32 meteres

hope this helps