>>13525624you're confusing EMFs from a static charge (which lightning is an example of) and an EMF from a voltage source
a static potential exists whenever there is a difference in the quantity of charge between two objects. If the objects are brought together (or somehow a conductive path is created between them, as in the case of a static shock or lightning strike), the objects will try their best to equalize the quantity of charge between the two objects.
Does this create a current? Yes, technically, as there is a net movement of charge. Is it a long lasting current? No. This is what's being depicted in OP's pic. If there is a charge distribution between the wires/lightbulb and the bathtub, a small current will exist for a fraction of a second as the charge is equalized.
The sheer existence of this charge balance inequality is what creates an EMF/voltage between the two objects. Once that imbalance is corrected, the EMF ceases to exist.
When you have a continuous electric circuit, it's not a charge inequality that generates the EMF. It's a distinct power source that has a voltage potential between its terminal points; due to, say, a chemical potential between the terminals. Connect the two points, and it will also try and balance the potential like with the static example. However, by the power source's nature, it can sustain an EMF for significantly longer than a charge distribution can.
>is that not a one-way flow?no, because there is an equal movement of positive "electron holes" moving to replace the excess electrons from the other object
>negatively charged lightning makes up such an overwhelming majority of all lightningdon't forget that positive strikes move an order of magnitude more charge (in this case, electron holes) than negative strikes do, so even though they occur much less often, they still on the average move the same amount of charge
