XPost: sci.electronics.repair, uk.rec.audio, uk.tech.broadcast   
   XPost: uk.tech.digital-tv   
   From: david.looser@btinternet.com   
      
   "J. P. Gilliver (John)"  wrote in message   
   news:f0bXgxX4wwKPFwWX@soft255.demon.co.uk...   
   > 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.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)