Light Bulb Brain Teaser

  • #1
901
2
This is a pretty easy problem, there is a room that is enclosed and all of the walls are opaque, there is no way to know what is going on inside from the outside (you are on the outside). There are three switches outside in which one of them has a circuit that flows to the light bulb. You can only go in one time to check which switch turns on the light bulb, how do you find out which switch is the one that turns on the light bulb?
 
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Answers and Replies

  • #2
901
2
Has anyone made an attempt?
 
  • #4
As far as i recall the person outside must flick a switch. Then wait a bit. Then he/she goes in. If the bulb is off and cold the switch flicked before entering is a dud. If the bulb is on, well its obvious. Something like that anyway.
 
  • #5
This question is very old.
You will switch on 1 bulb and wait, then after some time switch it off and switch on another bulb and go in. There will be one bulb glowing, one hot, and one cold and not glowing
 
  • #6
1
0
This question is very old.
You will switch on 1 bulb and wait, then after some time switch it off and switch on another bulb and go in. There will be one bulb glowing, one hot, and one cold and not glowing
There are three bulbs in your solution while there is just one in the initial problem...
 
  • #8
22,089
3,289
Well, there are other methods than feeling the bulb to see if it is warm: leave one switch alone, put one switch on, and put one switch just in the middle.
If the bulb is off, then it's the first switch. If the bulb is on, then it's the second switch. If the bulb is flickering, then it's the last switch.
 

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