Question: Can someone explain the exact function of the ARC reactor in Tony's chest, because it seems to vary from movie to movie? Sometimes it powers the magnet keeping the shrapnel out of his heart (1,3 & Avengers), which is why he throws it away after surgery. However sometimes it appears to be powering his heart directly (1), yet he can go for short periods of time without it (2). Mainly, however, isn't it required to power the suit (1 & 2). The Iron Monger needed one (1), Whiplash & War Machine both needed one (2), but Tony's suits in 3 & Avengers appear to work even when he's not in them?