Using 7 core trailer wire for mains lights

[The Natural Philosopher]

well I'd use it anywhere a test engineer might be expected to put a test probe to check it for some meaningful reason...

[Chris Green]

Yes, but it would imply +ve or -ve with respect to zero/earth/chassis surely so would never mean zero/earth/chassis itself.

[Dave Plowman (News)]

Can make a great deal of difference with audio. Actual earth is generally only connected at one point. Grounds a different matter.

Using all the various terms as interchangeable only leads to confusion,

[Dave Plowman (News)]

Not generally on a car wiring loom. Obviously things like car radios can have internal rails that swing either side of 0v.

All cars are negative ground these days so it doesn't much matter. But even in the positive ground days the (+) & (-) was only really shown at the battery. As everything had a common ground - the bodywork.

[Adam Aglionby]

Bulgin PX0551/2 cable plug and chassis socket, about early 2000`s Bulgin PX0956/9 Cable Socket and chassis plug appeared meaning that extensions didn`t have a live male plug on end.

[Dave Plowman (News)]

Other than cars with a glass fibre body, I've not seen any where all the ground wires are run to a single point. Would push the cost of the loom up considerably. I'm willing to be told different, though.

[DICEGEORGE]

i seem to rmember from somewhere that the old positive earth vehicles used to rust faster than negative earth vehicles for some reason to do with chemistry which is why they changed them all to negative earth

- my 1963 bedford bus was originally positive earth but converted to negative earth before my time

- many live wires were black, and earth wires red! [g]

[Dave Plowman (News)]

All vehicle electrics were originally negative ground. IIRC, the change to positive ground was said to improve plug and points life.

But not every UK maker changed to positive ground - Rolls never did.

Lucas wiring (BS colours) never used other than black for ground.

But other countries and makers had different standards - just as with main wiring colours.

The change back to negative ground came about with the increasing use of electronics.