Another Interlude and Final Change in Direction

So far I have been looking at magnet motors incorporating only permanent magnets. The difficulty apparent with such magnets is that they cannot be switched.

It would seem that better-performing devices could be made having at least some magnets that could be switched on or off as required. There is one obvious candidate for this: the electromagnet.

A large scrapyard electromagnet, shown in the "switched-on" state.
Image from https://www.sinfo-t.jp/eng/lifmag/scrap.html

In following posts I'll look first at the issue of electromagnetic attraction (briefly), then at electromagnetic repulsion (in more detail). I'll also take an extended look at a problem I've been investigating for a long time, that can be summarised with the image below:—

A disc rotor carries an arc-shaped permanent magnet which is initially attracted,
and is then repelled by a toroidal electromagnet.
(Bearings, framework, electromagnet inner coil layers etc not shown)

Is energy conserved overall when the permanent magnet in the rotor is attracted-in to the unenergized electromagnet's core, and is then immediately repelled-out by supplying a short pulse of electricity to the electromagnet's coil? In a repulsion case like this, a large portion of the electrical pulse's energy can be ultimately returned to its source. The question is — how much of that electrical pulse energy is lost compared with the total mechanical energy gained?