If you crank a generator in space...

[linux kid]

I am confused about where the electrons come from when electricity is generated. Is it from ambient air? So this means A generator would not work in space?

[cesiumfrog]

They come from your appliances.

A generator works like a water pump. Electrons are sucked in at one wire, and squirted down the other wire at higher electric pressure (a la voltage). It would all stop working if electrons weren't able to recirculate back again (indeed, your lights go off whenever you break open this circuit).

[linux kid]

so there must be a certain amount of electron available. And what if you somehow kept removing those electrons what would happen to the appliance (eg. light bulb)?

[cesiumfrog]

the point is that you can't remove the electrons. the best you can do is try to pump a lot of them up to one end of a wire (but this is hard to do because it leaves the other end positively charged, so the electrons are attracted to move back again somehow), and your appliance just stops the moment the electrons aren't moving through it anymore.

..actually, what I've described is the simpler case of DC. In the real world of AC, what the generator does is more like making the electrons in the connected wire vibrate (not significantly moving electrons in any direction overall, not going anywhere, hence not coming from anywhere).

[linux kid]

Oh...I get it now. Thanks.