Is effective diameter the outer overall diameter of a 7-strand earth wire, (about 2.1 mm), or the copper-only diameter based on 7 x 1 mm strands. (2.645751 mm) ? (Refer to answer on multi-strand wire inductance).


Diameter Factor is the ratio of an outer diameter to the diameter of each strand.

It assumes a perfect circle and no insulation. I looked up the value of D.F. and found it was 3.0 for 6 to 7 strands.

enter image description here However for much larger numbers of strands elliptical wire shape results in fewer strands for a fixed D.F.

"Effective Diameter" must be the equivalent diameter of a single solid conductor.


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