In chemistry lab we were learning electrolysis of water, the process turns them into oxygen and hydrogen. We had a beaker of water with anode and electrode in it. There was a function generator of low voltage and we’re supposed to plug the cables into it for current supply. There was also an outlet on the side of the sink table, providing 220V 60Hz AC voltage.

I plugged the two cables into the outlet. (Human safety voltage is 15V AC)

The beaker of water started boiling with gas and sparks coming out, the beaker jumped up a couple inches and spilled a lot, as I quickly pulled the cables out.

I didn’t tell anyone, only my deskmate witnessed this so I continued the lab session like nothing happened but I’m pretty sure it could gone really wrong.