Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

3 rooms 3 bulbs

  1. Jul 26, 2007 #1
    there are 3 rooms upstairs each room has one light bulb but the switches for the bulbs are situated downstairs and you dont know which switch corresponds to which bulb. the switches are turned off initially ... you can turn on/off the switches any number of times you want, you can go upstairs only ONCE and need to figure out which bulb(room) corresponds to which switch. You cant get anyones assistance for this and you need to figure out yourself. do u know how.

    The problem is I dont know the answer to this question :smile:
  2. jcsd
  3. Jul 26, 2007 #2


    User Avatar
    Gold Member

    Assuming incandescent bulbs, this is a really EASY one. Just think about it.
  4. Jul 26, 2007 #3
    flick on two of the switches, wait 5 minutes, turn off one of the two switches you originally turned on, go up stairs, check to see which one is still on, obviously corresponding to the switch you flicked on but did not flick off again. Then go to both lights that are off and see which one is hot to the touch.

    end of text
  5. Jul 26, 2007 #4


    User Avatar
    Gold Member

    Yep, that's how I figured it too.
  6. Jul 26, 2007 #5
    Yep yep....

    And it is also probably assumed that time really isn't a factor. Which, if that's true, you could almost do it with flourescents as well.
  7. Jul 26, 2007 #6

    OK this is suppose to be the correct answer aparently. tx guys
    Last edited: Jul 26, 2007
  8. Sep 11, 2007 #7
    the answer

    firstly get on one of the switches for 10 min or less
    then get it off
    2nd... get on one of the switches and keep it on .
    go up stair and feel wich one of the off light is warm and wich one the cold
    the warm one is no.1
    the on light is no.2
    the off light is swich no.3

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: 3 rooms 3 bulbs
  1. Quiz 3 (Replies: 15)

  2. 3 and Up (Replies: 16)

  3. Classico 3 (Replies: 1)