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‘At the stroke of midnight, your brother will be hurtling sideways at an altitude of 150 meters’ is a regular physics prediction about your nonmagical trebuchet, whereas ‘you are cursed to build a brother-launching trebuchet’ falls out of the Lagrangian.
Electromagnetics are dark magic and there is no way to teach it in any simpler terms that make it plausible without dark magic.
Even if you get all the concepts down. If you start asking “why”. The only real answer is, because in 73 BC an egyptian, a roman and a greek magician met in a basement in Kathargo to perform the most heinous ritual. But since the roman guy had a lisp in saying his incantation, instead of unleashing the demons of hell onto earth, electromagnetics becamse what they are.