And the wire it’s made out of is usually pretty thick. Certainly you’d get far less resistance in the wire than in the air gap, and given all of the vagaries of air, probably far less than the typical variation in the resistance of the air.
Yeah, even though coat hangers are typically steel (a poor electrical conductor), they are pretty thick (or they used to be… they seem pretty flimsy these days), and 50 mA is basically nothing.
My coat hangers are varnished, and even after carbonizing when the arc passes through it, that resistance probably also dominates the conductors themselves. Though as you say, the air gap is going to be the main factor by far.
We used ours to light our cigarettes.
My first week in the dorm was orientation week and the cafeteria was closed. I used an appliance cord and two forks to create the world’s best (and most dangerous) hot dog cooker. One wire around each fork, one fork in each end of the hot dog, plug it in (please do this in the correct order), and 30 seconds later the hot dog is ready to eat, cooked in its own juices.
So now I’ve learned about another kind of Jacob’s ladder. When I saw the thread title, I assumed the actual rope ladder. You know, rope stiles and wooden rungs. I thought, “A practical use for a Jacob’s ladder? What? In addition to climbing up or down?”
Can you guess that I was a biology major and not in physics or electrical engineering? No mad scientists (nor much high voltage equipment) in our Biology Department.
It does compare them to “arc horns” however, which do have a practical use. Basically arc horns are designed so that a voltage high enough to damage equipment will be powerful enough to arc over and be grounded through the arc horn instead of something less expendable. Not quite a Jacob’s Ladder, but it does have similarities.