For round wire, we assume that the cross-section area is the important
bit, so a round wire with diameter $D$ ought to work as well as
square wire with side $S$ if $S^2 = \pi D^2/4$, i.e.,
For round wire, we assume that the cross-section area is the important
bit, so a round wire with diameter $D$ ought to work as well as
square wire with side $S$ if $S^2 = \pi D^2/4$, i.e.,