A comment in another thread led me to think about an experiment which can hopefully test the validity of the pointing vector theory for a dc current. I’m very unsure of the outcome of this experiment but what the heck. Here it goes: the Poynting theorem states E x H is power per unit surface area. First consider a single winding with dc current I. We know that H is higher at the surface then at the centre, but E is everywhere the same running length wise. Now think of a coil made out of fairly thick wire say 10mm square with say 20 windings. Similar as with the single wire, a winding in the centre will have a smaller H field then the ones at the outside. Therefore since all winding have the same surface area, current and E field, the outside windings should get hotter than the inside ones. Therefore 2 small thermocouples should be able to pick up the differential. Note however that the middle one will very quick receive thermal energy from the surrounding wires. Any thoughts?