"A light bulb is hanging in a room behind a closed door. There are three switches in the hallway outside the room. One of these switches belongs to that light bulb. The light bulb is not lit and the switches are in off state. There is only one chance to visit the room. How can it be determined which of these switch is connected to the light bulb?"
Assuming that these are incandescent light bulbs, turn on 1st switcch for few minutes and then turn it off. Then turn on second switch & enter the room. If the bulb is lit then the second switch is the answer - if not then touch the bulb with your finger to see if it is warm. If so, then the switch is first one you tried. If neither is the case, then your answer is switch #3.
Jay
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