If you don't put any ohm at all, miss amp just gets pushed all the way through the tube really fast without doing anything. Like if the next part of the tube is an LED, all that amp coming through would make it glow way too bright and then explode or something.

There's a second thing you can do with two ohms. If you line up two ohms one after the other, then a little volt appears in the chamber in the middle between them. But miss middle volt is a smaller version of the big volt, and her size depends on how tight your ohms are relative to each other.