The essential ideas behind the monopole shift can be captured in a simple toy model. You will understand how the phenomenon that we call ‘monopole shift’ can arise in simple mechanical systems as well. It is not restricted to atoms or other quantum systems.
The content of this video is written down in this research paper(up to Sec. 3.1 of the paper). You can use that paper as optional reading with the video. This paper is available on Perusal as well — feel free to add notes and questions there (optional).
Think now about the following puzzle, and submit your suggestion to resolve it to the forum underneath. Feel free to comment respectfully on the proposals by your colleagues:
We had concluded that the electric monopole shift always gives a positive contribution to the energy levels. However, when comparing toy models 0 and A, you might have noticed that the additional charge (-epsilon) lowers the energy of the toy atom instead. Do you see a logical loophole to resolve this (apparent) contradiction?