If I remember correctly, the appliance uses energy. Therefore the return does not need to be so heavy as the supply.
I suspect my return for everything other than the starter, is returning via the accelerator cable.

No. There can't be any energy used, if the electrical circuit can't supply the energy. That's why the return path needs to be as good as supply...

The best example on car, the starter motor. There is large supply and earth wires, but does it use energy when it isn't full connected? And how well it will work if other one, supply or earth (return) gets worse..?

As Jasu has already pointed out, the same current flows through both supply and return leads in a circuit.
On a 2CV, if the main earth strap to the engine/gearbox is loose or disconnected, that small earth strap to the bodyshell will melt trying to carry the heavy current demanded by the starter motor.

It clearly needs a return, but the energy going through it must be less, because the appliance is consuming some energy. Can't say I completely understand the science, but I do know you can't have perpetual energy.

About sciense. You talk about energy, what is Watt with electric systems. And Watt is Voltage multiplied by Current, and if you havent' goo enough wiring, you can have Voltage but at worst case no Current at all. So, try to multiply Voltage with zero Current, how much you have energy in Watt..?

Is that possibly to understand at all? Really hard to explain with foreign language...

Jasu
I think we are talking cross purposes.

There 2 points I was making.

1. I have an earth from the battery to the gearbox, but not from the battery or gearbox to the body of the car. I was curious as to how the headlights for example, were getting a circuit back to the battery when the engine is rubber mounted. It must be making a circuit somewhere. I suspect it is the accelerator cable.

2. I was commenting on what Taskos was saying about the thin earth going to the body. This only needs to return the energy used by the lights etc.

However, I still maintain the return does not need to be as heavy as the supply because the appliance consumes some of the energy. I'm not suggesting the starter can have a thin return, just that it does not have to be as heavy as the supply.

Roger,
as already mentioned, this theory is incorrect.
In any circuit where the supply and load(s) are connected in series, the resultant current will be the same at any point in that circuit.

"Current in series circuits.
The current is the same everywhere in a series circuit.
It does not matter where you put the ammeter, it will give you the same reading."



See...
http://www.bbc.co.uk/bitesize/ks3/scien ... evision/6/

Ok. I accept that. I would have thought that the resistance in an appliance would reduce the amps and voltage.

But like I said, I don't really understand the science.

And the missing return, is returning where?

The missing return, an earth wire, when it is bad the current find another route, choke cable, speedo cable, throttle cable etc, anything what conducts enough is usable...

And also bulbs what aren't on, nice example from headlights, if the earth wire is bad on one headlight, then that bulb will illuminate by both filaments, and also the other filament on that side where is good earth...

Thanks Jasu
Just as i thought. And as you say, it will find away back if it can.