Problems with ground with batteries

[Kerso1991]

Hiya, I'm a bit of an intermediate in electronics and I am moving into oscillator territory and am thinking more about "ground" rather than "the negative side of the battery". Obviously, using -ve voltage as ground has some setbacks with dc-ac oscillators as current can only flow if there is a true 0v reference point(when the ac signal goes into the -ve phase then the -ve side of a battery is absolutely useless). What can I use as 0v rather than -9v on a battery that'll actually work? Considering that current cannot flow from the -ve side of one battery to the +ve side of another without the oposite polarities being connected, I'm presuming that current also cannot flow from the +v side of one battery and the ground on a mains plug.
Any help would be great

 

[jim hardy]

Do you believe in Kirchoff's Current Law?

Current only can go back to its source.
If "Ground" happens to provide a path back there , current might take it. Or it might not, if there's a better path.

The "water" analogy mis-leads almost all beginners because we see water fall from our garden hose to "ground".
It's gravity causing that, not some magical affinity of water for ground.

Electricity doesn't care a whit about gravity.
It has no magical affinity for "Ground" (which I prefer to call "Earth" to distinguish from "Circuit Common" aka 'ground' )

as current can only flow if there is a true 0v reference point(when the ac signal goes into the -ve phase then the -ve side of a battery is absolutely useless).

I cannot parse that statement.
Can you slow down and re-phrase it one thought at a time?
"A question well stated is half answered".

There exists a concept in circuits known as "virtual ground" midway between supply rails... maybe that's what your are considering? Try a few searches on those words.