What is this thingy for?

[tw]

Originally Posted by xoxoxoBruce

I suspect they stop static electricity or maybe even voltage surges, but I don't know.

The ferrite block is an RF filter. But it does not work (well) for frequencies in the AM (longwave) bands. It is mostly for eliminating shortwave, FM, and TV interference. For example a monitor operates in the tens of megahertz range. This is shortwave. Ferrite bead is part of a large system that blocks radiation of those frequencies. Other protection (not the ferrite bead) inside electronics should also make interference not occur to an adjacent AM (longwave) radio.