Why did Tony Stark use an electromagnet?

Question

We all know that after an unfortunate experience with a bomb that literally had his name on it, Tony Stark needed a way to keep the unfortunately acquired shrapnel from getting to his heart, so he invented himself a handy little arc reactor that powered an electromagnet that kept it at bay.

But... why an electro magnet?
It make sense that he needed the reactor to power the suit he used to escape, so using it to power an electromag was a good cover story...
But it seems like a normal magnet would have been sufficient to keep him alive after he got to safety.
Is there some reason a normal magnet wouldn't have worked? This would have certainly have helped when he was dealing with palladium poisoning in Iron Man 2.

Answer 1

In the film universe, the simple reason is convenience. When Tony is first injured Professor Yinsen jerry-rigs an electromagnet from a car battery because he doesn't have access to a sufficiently powerful fixed magnet. Later on, Tony switches the power source to a miniaturised arc reactor which then doubles as the power source for his super suits (as well as a guarantee that only he can use them).

It's certainly possible that there are revival reasons behind it.

• A fixed magnet might not be powerful enough.

• It may offer other complications when combined with the arc reactor.

• It may be that the chest unit contains some kind of feedback mechanism that allows the field strength to be changed as needed (hat tip to Fjtagn for that idea)

• Heck, it might just not leave enough space for the arc reactor but these are all pure guesswork.

Obviously later we do see him putting arc reactors directly into the suits but that's a whole 'nother question.