Copper Conducting Considerable Current

The latest kitchen acquisition (no, we don’t spend all our money on buying things for the kitchen) is decent frying pan. We’ve spent too long with frying pans that are about as flat as the Southern Alps.  It’s a copper-based pan, which probably accounts for its expense, with a stainless steel surface.   The reason for the copper is that it conducts heat extremely well, meaning that the surface of the pan will respond nice and evenly and quickly to the heat from below. 

Copper is probably better known, however, for conducting electricity rather than heat.  Its electrical conductivity is extremely high, and, coupled with its ease of working, there is no surprise that electrical wiring accounts for a huge amount of copper. 

These two facts (high thermal conductivity and high electrical conductivity) are not unrelated.  This is because the processes by which they occur are very similar. Electricity is carried by movement of electrons, and electrons are also a major carrier of heat. In copper, there are a lot of electrons that are highly mobile, and hence it has both high electrical and thermal conductivity.

In fact, in metals, the two follow (approximately) a simple relationship – the ratio of the thermal conductivity to the electrical conductivity is approximately proportional to temperature.  This is called the Wiedemann-Franz law. One can ‘derive’ this relationship using some fairly simple hand-wavy physics arguments, though to do it properly is not so easy. I’ll be doing the hand-wavy approach (for those that want to know, it’s the Drude theory) with my second year students soon.


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