Hello everyone. I'm building a Jacob's Ladder just for the hell of it, and am currently trying to figure out how far apart to place the two rods so that an arc will pass over them. Paschen's law seems to vary depending on the shape of the electrodes; the equations that google brings up are probably for parallel plates, as I tried plugging in the numbers just for the hell of it, however not surprisingly, this didn't work because my resulting answer didn't make any sense. Is there any way to calculate the distance between the two rods, or is the measurement entirely empirical? Wasting boards isn't exactly a preferred method.