iMac tripping breaker just by plugging it to electricity, without even pushing the power button!
DANGER! DANGER WILL ROBINSON! Don't try to plug it in. That sounds like a hard short. Get it to an Apple Store or an authorized repair center. Hopefully, it's under AppleCare or some type of warranty. Each time you try to plug it in you risk doing irreparable damage to the iMac or, worse, possibly causing a fire or life-threatening shock hazard.