Can an isolated AC system like a generator which is not system grounded will be able to give me a shock if I touch it one wire? I guess it should not, because then there would not be a path back to the source (the generator). But I highly doubt it and I was proved wrong in case of an inverter whose none of output wire were tied to ground still was able to glow a neon test screwdriver... But an isolated DC system (like a battery) will behave as I had thought. No current would flow through my body to ground if I touch it...
There is a nice example: Tucker Phone. https://en.m.wikipedia.org/wiki/Tucker_Telephone
When i was in the military, tried it on myself, it's quite painful.
Of course, you have to hold two wires with two hands.
Short answer is yes.
I once had an "isolated" generator that was not system grounded. I thought I was safe from shock. Turns out, you can get quite a healthy shock.
Isolated in terms of a generator generally means the neutral is floating, not that it is 100% isolated from ground. To prove it to yourself, take a multi-meter, and measure the voltage from the "isolated" neutral to earth ground. My generator measures about 60V, and gives you quite the tingle if you touch it!
Longer story: I was working on a branch circuit on my cabin, the breaker was "off" but my isolated generator was running to power the other circuits. I touched the neutral wire and received a very healthy shock. I touched it again out of disbelief, and shocked my self again. It was when I measured the neutral wire with my DMM, I realized that my isolated generator was not as isolated as it should be.
An AC generator is not the same as an DC battery.
If you have an unconnected thousand volt battery, you can safely touch one of the terminals. Because it is DC.
Not both obviously, since then you'd have an electrical path.
However, with AC, the electrical path will include capacitors.
For a generator for example, all the winding in the grounded housing will have a parasitic capacitance to ground. So will you, the large body of water walking on the ground.
Can an isolated AC system like a generator which is not system grounded will be ble to give me a shock if I touch it one wire?
Yes, if there is enough leakage current.
Which is why a Tesla coil works with fluorescent lights, if you hold them.