Which wire is generally switched, hot or ground?

[Blue Chips]

Not nearly to this stage as yet but it popped into my mind that the ground wire is switched, say to a trim motor or navigation lights. Did do some searching but found nothing stating.

Thanks
Ken

[WLIU]

In the western hemisphere the "hot" is + voltage and is switched. Most amateur built airplanes are +12V DC.

If you live in another hemisphere or a third world nation, your mileage may vary.

Past results are no guarantee of future performance. Do not try at home.

Best of luck,

Wes

[Blue Chips]

Thanks Wes, found a few schematics and they agree with your answer.
Not sure where I got the switch negative wire from, still seems right in my head but not on paper.

[1600vw]

Electricity flows from + to - or positive to negative. So we want to cut the power source. If you cut the ground and something goes to ground you still have power. But if you cut the power and something is still going to ground you have no power.

Tony

[Blue Chips]

That makes sense!

Thanks
Ken

[WLIU]

"Electricity flows from + to - or positive to negative"

I have to ask whether you have ever owned a British car? The builders of the old MG's etc seem to have a different opinion as to the physics. Hence my poor attempt a humor in my post.

Best of luck,

Wes
N78PS

[Bob Dingley]

I always wondered about the origin of "Lucas invented darkness" then I got an MG.

[rwanttaja]

Electricity flows from + to - or positive to negative.

The irony is that the actual physical flow is negative to positive (the electron flow). They just retained the "definition" that "current" flowed from positive to negative.

Some applications do switch the ground side. I had a 1946 Willys Jeep as a kid, and most of the buttons actually grounded things, rather than applied power to them. If you're running a long wire back from the device, it can be safer to make that the ground wire. If it shorts out, the device comes on, rather than producing a dead short to the battery. For a 16-year-old kid with cheap hardware-store wire, an ignorance of grommets, and a lack of hard-won understanding on how sharp edges of metal will saw through insulation, it was DEFINITELY a safer way to go.

Ron "Why is my horn honking?" Wanttaja

[WLIU]

If you owned an MG then you know that Lucas invented the intermittent windshield wiper also.

Best of luck,

Wes
N78PS

[Dave Stadt]

Electricity flows from + to - or positive to negative. So we want to cut the power source. If you cut the ground and something goes to ground you still have power. But if you cut the power and something is still going to ground you have no power.

Tony

I was taught lo so many years ago and made a living in electronics for decades believing those electrons leave the negative side and travel to the positive. I just checked and physics has not done a 180. Typically, the positive side is switched but as Ron says there are legit reasons to switch the negative side. Don't know if AC 43.13 has anything to say about the matter but it might be worth a look.