Yesterdays attempts had some promise. What I really want to end up with is two different models showing the structure of atoms. One the Rutherford idea and one Thomson’s Plum Pudding idea. Eric Rogers had a couple of sketches in Physics for the Enquiring Mind:
One of the weaknesses of my teaching of this is that I don’t think I sufficiently explained the outcome of shooting the marbles across the two models. I think that’s pretty common as you can only buy the Rutherford model. (The Rutherford model is top left and the two bottom right). So I’d like to be able to make a Thomson Plum Pudding model (top right) and a Rutherford one in this workshop. Then you can clearly see that one gives lots of deflections but smaller (Thomson) and one gives lots of very small deflections or no deflection, plus the occasional very large deflection (Rutherford).
This is the “workshop” in the other sense of the word:
So we aren’t talking complicated tooling here. Heat gun, on the right, is the main tool for this.
Today I produced a Rutherford model that I think I’d be happy to use in class:
It’s not perfect but it is better than yesterdays attempt. Near enough for me to get away with it. I’ve yet to try rolling marbles at it though. It’s not going to be an inverse square curve but I’m not thinking that I’d use this quantitatively any way.
The first Thomson attempt didn’t go as well.
The plate (positive “pudding”) with valve ends (“plum” electrons) on is the former, I want the inverse of that. I tried it with this thin white plastic but it seems to heat unevenly. I was hoping it would just sag down onto the plate and stick up where the valves were. When you turn it over you’d see a low hump with depressions in it – like the drawing in the first picture, top right. That’s looking much trickier.