Skin effect is a very well-known phenomenon, and isn't negligible even at mains frequencies- from Euler's link:

In reference to en.wikipedia.org/wiki/Skin_effect#Examples:

In Engineering Electromagnetics, Hayt points out that in a power station a busbar for alternating current at 60 Hz with a radius larger than one-third of an inch (8 mm) is a waste of copper, and in practice bus bars for heavy AC current are rarely more than half an inch (12 mm) thick except for mechanical reasons.

Those "mechanical reasons" are why overhead high-voltage pylons can get away with aluminium as the conductor (cost and weight) with a steel core (tensile strength)- the current doesn't penetrate down as far as the steel.

Edited by billford (Fri 10-Apr-15 20:00:05)

Just to add to the other comments.

169M is referring to the length of cable that has been used. It will start at 0 (zero) and increment every metre so at 169 indicates there is 136m remaining. It is often quite useful when trying to work out which cable is which in a bundle.


AND

Don't open the box, just pull it from the centre! The cable is laid so that as you pull straight out there will not be any annoying twists.

Edited by MHC (Fri 10-Apr-15 23:55:40)

In reply to a post by MHC:

169M is referring to the length of cable that has been used. It will start at 0 (zero) and increment every metre so at 169 indicates there is 136m remaining. It is often quite useful when trying to work out which cable is which in a bundle.

A very helpful tip!

Don't open the box, just pull it from the centre! The cable is laid so that as you pull straight out there will not be any annoying twists.

And another!

Thanks to all for your very helpful, enlightening and encouraging comments