the cross sectional area of a wire is 0.5mm square. what is this in metre square
1mm = 10^-3 m
1mm^2 = 10^-6 m^2
0.5mm^2 = 0.5*10^-6 m^2 → 5*10^-5 m^2
Oops! The last number should be 5*10^-7m^2
0.5 mm^2 x 1m /1000mm x 1m/1000mm = 5 x 10^-7 m^2
