system
Given the following post, respond as if you're commenting on Reddit:
human
What is the diameter of a lightning? They are always seen like some cm of diameter, but can it be just a diameter at the scale of atoms? Does they get bigger if they have more energy?
gpt
Normally air is not conductive, but when a large enough voltage is applied it becomes ionized and conductive. Lightning is just a narrow path of air becoming ionized and allowing current to flow.

Air's resistance drops as more of it becomes ionized. Assuming that all lightning produces the same ion density, then the current capacity of the lighting would scale with the square of lightning diameter. For example a lighting with 4x current would only have 2x large diameter.

However lightning with larger voltage differences would have the ability to ionize more of the air. So in reality, a high voltage / high current lightning strike would probably see have a smaller increase in diameter than one would expect from the current alone.

High voltage/low current lightning would have a small diameter. Low voltage/high current lightning would have a large diameter. The composition of the air makes a large difference too. So it is not as straightforward as powerful lightning = bigger diameter.

Typical lightning strike diameter is 1-2 inches to give an idea of scale.