# which switch corresponds to which light bulb?

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There are three switches downstairs. Each corresponds to one of the three light bulbs in the attic. You can turn the switches on and off and leave them in any position.
How would you identify which switch corresponds to which light bulb, if you are only allowed one trip upstairs?

posted Sep 2, 2014

First we have to turn ON first switch and have to wait for 5 minutes, then we have to turn OFF it and turn ON the second switch and we have to check by going upstairs, the bulb which turned ON will corresponds to the second switch and we have to touch the remaining 2 bulbs, the one which is hot will corresponds to the first switch, the one which is neither hot nor ON will corresponds to the third switch.

answer Sep 2, 2014 by anonymous
+1 vote

Turn ON first switch and then wait for some moments.And Switch Off it, Then Switch On Second One.Go Up Stairs. Check the bulb which is glowing , that is Second Switch Control. Then Test remaining two with hand, Which feels your hand heat , that one is first switch control.

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You are standing outside a closed door. On the other side of the door is a room that has three light bulbs in it. The room is completely sealed off from the outside. It has no windows and nothing can get in or out except through the door. On the outside of the room there are three light switches that control each of the respective light bulbs on the other side of the door.

Your assignment is to determine which light switch controls which light bulb. You are allowed to enter the room only once, and once you come out, you must be able to state with 100% certainty which light switch controls which light bulb.

There are 3 switches downstairs, each corresponding to one of the light bulbs upstairs.
How can you figure out which light switch goes to which light bulb by only making 1 trip upstairs?