Freezer-Extension Lead Exclusion-Guarantee.

In all cases the actual contact area is a very small fraction of the total metal surface - as noted cylinders inside cylinders have only stripes of contact area - the springyness of the socket is key to a decent grip with some wiping action.  I suspect we all have at some point found a cooked 13A plug stuck in the socket, and had to change both, although you may think that we only need a square mm or so of cross-section for the current rating we are trying to achieve. In practice, with corrosion, mechanical mis-alignments, wear on the contact faces and so on, we may not get even that.

I nice clean 13 plug in a nice clean 13A socket probably has quite a bit of rating in hand if the surfaces are all perfectly true and polished. The problems arise when after a while this is no longer true. Similarly, heating of the fuse and its clips, over and above the fuses own ohmic  self-heat, can be caused by the same age related issues, And then we have the problem that heat tends to relax most of the materials you might like to use for springs, and it all spirals down pretty sharply.


I think the CEE form plugs are more successful under overload and abuse becuase there is much more metal mass for cooling, and being more enclosed, corrosion and damage are slower to appear. not because of some property of round  vs. square pins.

In all cases the actual contact area is a very small fraction of the total metal surface - as noted cylinders inside cylinders have only stripes of contact area - the springyness of the socket is key to a decent grip with some wiping action.  I suspect we all have at some point found a cooked 13A plug stuck in the socket, and had to change both, although you may think that we only need a square mm or so of cross-section for the current rating we are trying to achieve. In practice, with corrosion, mechanical mis-alignments, wear on the contact faces and so on, we may not get even that.

I nice clean 13 plug in a nice clean 13A socket probably has quite a bit of rating in hand if the surfaces are all perfectly true and polished. The problems arise when after a while this is no longer true. Similarly, heating of the fuse and its clips, over and above the fuses own ohmic  self-heat, can be caused by the same age related issues, And then we have the problem that heat tends to relax most of the materials you might like to use for springs, and it all spirals down pretty sharply.


I think the CEE form plugs are more successful under overload and abuse becuase there is much more metal mass for cooling, and being more enclosed, corrosion and damage are slower to appear. not because of some property of round  vs. square pins.