[David Looser]

"J. P. Gilliver (John)" wrote in message
...
In message , Mortimer
writes:
[]
While we're talking about electrical safety, what is the current (scuse
that unintentional pun) advice on extending the lead of a freezer? I know
you have to use cable that is rated for 13A (1.5 mm^2 wire rather than 1
mm^2) and conventional extension cables must be unrolled to avoid
inductive heating. But providing you use a cable of the correct
[]
I don't _think_ it's _inductive_ heating they're that concerned about -
just air cooling, or rather the lack of it when a cable is wound onto a
reel (and tightly, as it often is).
--

Indeed. It's a common error to assume that the reason that cable drums
should be unwound when in use is something to do with inductance. Possibly
because its a coil, and wire is commonly coiled up to create an inductor.
But in this case it is, as you say, simply a matter of air cooling, or more
to the point the lack of it. The inductance of an air-cored coil of
relatively few turns would be insignificant at 50Hz and in any case the
inductances of the two conductors largely cancel out.

David.