DC current - does it travel inside the wire or just on the outside?
DC current - does it travel inside the wire or just on the outside?
(OP)
I know for AC, the push-pull forces the electrons to the outside of the wire (skin effect) but for DC, in a solid wire, does it only travel on the outside of the wire, or will it 'fill' the wire. The background of the question is, a busbar attached to a PCB, where a stud ties it to the "pad". From talking to some in the bus bar industry who alluded to the fact when a stud ties into a bar, the current only really carries on the outside of the stud, and the actual transfer of current happens primarily on the surface to surface contacts of the pad and the bar.
We are talking 60A @48VDC for this application.
Comments?
We are talking 60A @48VDC for this application.
Comments?





RE: DC current - does it travel inside the wire or just on the outside?
RE: DC current - does it travel inside the wire or just on the outside?
While the DC SHOULD fill a conductor, the spreading resistance of going around corners and through interfaces, etc., WILL cause non-uniform distribution of current.
TTFN
RE: DC current - does it travel inside the wire or just on the outside?
Gunnar Englund
www.gke.org
RE: DC current - does it travel inside the wire or just on the outside?
But the light still comes on when you flick the switch.
The purpose of this thought experiment is that it may change the way you visualize current flow in conductors. It will reinforce the 'voltage = pressure' analogy and highlight the importance of the empty valence positions (versus the electrons themselves).
The point for THIS thread is that the current will not be sufficient to be accurately described as 'filling' the wire.
RE: DC current - does it travel inside the wire or just on the outside?
Excellent point. What, then would be an indicator that one would have sufficient current to "fill" so to speak, the conductor? Red hot wire? Excessive voltage (pressure) drop?
rmw
RE: DC current - does it travel inside the wire or just on the outside?
RE: DC current - does it travel inside the wire or just on the outside?
If a conductor was carrying sufficient current that 'most' of the free electrons were on average 'moving rapidly', then the conductor would be vaporized in an instant.
RE: DC current - does it travel inside the wire or just on the outside?
rmw
RE: DC current - does it travel inside the wire or just on the outside?
You might be looking at a problem down the road.
If it's not built I would not hesitate to use both sides of the board as you are entirely discounting the bolt and the back of the bussbar. Look at any HotTub controller they all do the same thing (bolt flat bar to circuit board). They use both sides. At the very least you want to use both sides to help distribute *any* heat better.
RE: DC current - does it travel inside the wire or just on the outside?
Best way of doing this is to solder a heavy duty connector or spade terminal(s) to the board. Bolt carrying around 60 A does not sound like a good idea to me. Seen much less current burn boards around bolts that have come loose after a couple of years.
Gunnar Englund
www.gke.org
RE: DC current - does it travel inside the wire or just on the outside?
TTFN
RE: DC current - does it travel inside the wire or just on the outside?
Also...good idea on the compression springs. Hadn't thought about that before, so thanks
RE: DC current - does it travel inside the wire or just on the outside?
May I ask what this board is running?
If I can't that's okay.
I just like to learn.
RE: DC current - does it travel inside the wire or just on the outside?
I understand your point that the charge carriers are spread throughout the conductor volume, but it's just that the word 'filled' might leave a false impression. The only conductors that could be fairly described as being 'filled' might be some sort of superconducting nano-fibre carrying an extremely large current.
A phrase something like 'evenly distributed' is perhaps a more accurate than 'filled'.
I admit that it's a delicate distinction and pedantic point. Sorry about that...
RE: DC current - does it travel inside the wire or just on the outside?
TTFN
RE: DC current - does it travel inside the wire or just on the outside?
RE: DC current - does it travel inside the wire or just on the outside?