Electrical question about the direction of D/C current flow

[Soundguy]

don't forget Pouillet's law .. the larger the crossectional area, the lower the resistance.. the longer the length.. the higher the resistance. et. ( oversimplified definition )

AND.. the skin effect applies to alternating current. as the Freq goes up, skin depth is less.... ( again.. oversimplified.. )

 

[bcp]

Flow on the surface only?

If so, an insulated piece of copper tubing (nearly twice the surface) would carry almost twice as much as a solid wire of the same diameter?

Bruce

 

[jaotguy]

simple corrosion on the outer layer .. that green stuff is oxidation ( needs oxygen to make it ) ... so the wire is being exposed to air .... the oxidization does not conduct as well as the base metal ... also the reason for gold contacts and " silver wires ( oxidize less ) for critical applications ....

also the reason you're supposed to re-torque the feed wires in main breaker boxes , every so often...

 

[oldballs]

That would be a place where I would start looking, a switch in the line that is. Maybe the drivers door switch for the dome light?

Unlike earlier cars that I owned, there are no door switches that I can find....you know, those metal knobs that spring out when the door is opened and are pushed in when the door is closed. I can't find anything that controls the door(s).

 

[mikehaugen]

Unlike earlier cars that I owned, there are no door switches that I can find....you know, those metal knobs that spring out when the door is opened and are pushed in when the door is closed. I can't find anything that controls the door(s).

The ones on my car are incorporated into the latch.

 

[skyhook]

Flow on the surface only?

If so, an insulated piece of copper tubing (nearly twice the surface) would carry almost twice as much as a solid wire of the same diameter?

Bruce

It would not carry "twice" as much electrons, being hollow in the middle.
Therefore, it would not supply "high" amperage flow.

 

[oldballs]

The ones on my car are incorporated into the latch.

Thanks, Mike. Now if I can get my brain electrons flowing in the right direction, maybe I can fix this myself.

Cheers,
Mike

 

[joshlee]

I'll definitely keep that in mind. Good stuff to know.

Yep, thats why when you see corroded "green" cables, on the outside, when you split the cable open,
you know it's time for new cables "or' wire".
Electrons flow around the outer cable, believe it.



LOL, I'm no "Master Electrician", but i do have my masters in Electronics,
Think about this for a second.....
when you pull back a connector on your tractor and one of them "fall of" due to corrosion,
you strip back the wire to reconnect it only to find the wire is all green from humidity etc,
yet, when you cut that wire in half, it's nice and copper clean on the inside,
now ask yourself, "why" didn't it conduct.

 

[joshlee]

Oh okay. It sounds like there's a few guys on here that know the electrical field quite well, so maybe they give you some good advice. Good luck.

Unlike earlier cars that I owned, there are no door switches that I can find....you know, those metal knobs that spring out when the door is opened and are pushed in when the door is closed. I can't find anything that controls the door(s).

 

[Jkott]

One question I have (and am surprised of) is that there is no "network" or cat5 cables on cars yet. At least that I am aware of. But again, my experience of "new" stuff ends ~2008. I am sure lots has changed in the last 7 model years

Ever heard of Canbus? My 2006 GM is controlled by a data network. For example just a power and data line go to the passenger door to control the power windows, locks, etc. they eliminated a lot of weight when they eliminated many of hot power leads and went to various control modules.

Of course most old school mechanics have no idea how data communication works or how to troubleshoot it. That's why many people have such issues with electrical gremlins in modern vehicles. Eventually training will catch up and more mechanics will actually be able to fix the electrical problems as reliably as the mechanical ones.