There is a hallway with a set of stairs going into a room. in the hallway there are three switches. Two are dead, and one turns on the light in the room. You must figure out which light goes into the room with out look into the room while it is on. How do you figure this out?
You turn the first switch on, the second switch off, and turn the last switch on for a minute or so, then turn it off. Go into the room and if its on, its the first. If its off, its the second, and if its off and warm its the third