Incandescent light bulbs are officially banned in the U.S.::America’s ban on incandescent light bulbs, 16 years in the making, is finally a reality. Well, mostly.
“A windowless room contains three identical light fixtures, each containing an identical light bulb or light globe. Each light is connected to one of three switches outside of the room. Each bulb is switched off at present. You are outside the room, and the door is closed. Before opening the door you may play around with the light switches as many times as you like. But once you’ve opened the door, you may no longer touch a switch. After this, you go into the room and examine the lights. How can you tell which switch goes to which light?”
The solution is:
- Turn two switches on, leave one off
- Wait a few minutes
- Turn one of the “on” switches off
Now, when you enter the room, you’ll have one lit bulb, one warm unlit bulb, and one cold unlit bulb, letting you solve the riddle.
I think it’s along the lines of “you’re in a room with three lightswitches. They control three lightbulbs in a different room (so you can’t see them from the room with the switches). You get some time to use the switches, and then you go to the other room and have to guess what switch controls what lightbulb. You aren’t allowed to go back and flip the switches again once you leave.” The solution generally is to flip one switch, leave one off, and flip the last one on for awhile but then turn it off just before you leave to go to the other room. The lightbulb that’s lit obviously goes with the switch you flipped on, and the other two are off. One of these two will be warm though, because it was recently turned on, and that one goes to the switch you flipped on and then off.
It’s an old riddle where a room has three lights and outside the room is the panel with three switches. They’re not labeled and you don’t know which switch controls which bulb. You’re allowed to switch any two, then you get to open the door and you have to determine which switches control which lights.
The solution is, that you flip switch #1, wait five minutes and then flip switch #2. Then you immediately go into the room.
Two lights will be on, meaning the bulb that’s off is the third switch. Then you feel the bulbs that are on: the one that’s warm already is the #1 and the other that’s on but still cool is #2.
LEDs don’t heat up like that so this technique is broken.
