The situation is this: Inside a room there is one turning lightWhile out from the room they are found Three switches different. The door of the room is closed and there is no way to see if, pressing one of the three switches, the light bulb turns on. What we are sure is that one and only one of the three switches actually lights the light bulb.
How do we find out which switch is the right one if we can open the door only once and, once opened, can we no longer touch the switches?
The solution to the indovinel of the light bulb and the three switches
We reflect for a moment on the situation: we find ourselves out from the closed door And in front of us there are the three switches. As mentioned in the statement of the IndoVinello, from the outside we have no way to understand which of the switches is the right one, because the door is perfectly tight and therefore the light does not go from the fixtures. The only thing we can do is cele with the switches And, once our winning move was made, open the door to decree which of the switches actually lights the light.
If the switches they were only two, The situation would be very simple! We could turn on the first and open the door: if we found the light on, It would mean that the right switch is precisely what we pressed, that is, the first. In the event that instead the light had remained off, the switch would be the second, what we did not pressed, because as mentioned in the statement of the investigation, we know that one of the switches will certainly turn on the light bulb.
In our case, however, the switches are three And press only one switch is not enough for us! The ingenuity must be aguched and one found condition in addition to the light on that helps us to differentiate the three switches. Which feature could distinguish a light bulb, in addition to the light? If we think about it, one lamp that remains on for a long time … Scotta! Even if a clarification must be made: the “new” LED bulbs warm up much less than halogen bulbs. But this does not mean that they do not produce heat! There are no light bulbs that absolutely do not produce heat. In any case, this premise has been made, we found our second variable: The heat of the light bulb! So what to do?
Here we are the solution of the indovinel. Let’s put on On the first switch And we leave it lit for some time (maybe half an hour, to be sure that even a LED bulb warms up). Once half an hour passed, we turn off the first switch e We turn on the second. At this point we enter in the room and we will be sure we can understand which of the three switches is the right one:
- In the event that the lamp is on, The right switch is the only one located on on that moment: the second;
- In the event that the light bulb was offcomes into play the heat! We touch the light bulb: if it were hot, The right switch will be the first, while if it were cold The right answer is the third!
This is because before entering we left for a long time the first switch on and therefore in case he was the right one, in the time when the bulb remained on he warmed up. If, on the other hand, the bulb is off and cold, it means that it has never been lit, so the third switch will be the right one, because it has never been pressed!
