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Brain teaser #71325
10/26/06 05:16 PM
10/26/06 05:16 PM
Rewired  Offline OP
Joined: Jan 2006
Posts: 558
Hamilton, Ontario, Canada
This one was told to me by a plumber today at the jobsite. Its easy I figured it out [Linked Image]

You have 3 lights up in the attic of a building. These 3 lights are controlled by 3 individual switches in the basement of the building. You must identify which switch controls what light BUT, you can't obviously see the lights from the basement.
How do you identify what light is controlled by what switch without the use of any tools except maybe a stepladder if needed to reach the lights, and with only making ONE trip from the basement to the attic. Assume the lights could have just recently been on and might still be hot.


Work Gear for Electricians and the Trades
Re: Brain teaser #71326
10/26/06 05:33 PM
10/26/06 05:33 PM
rabbitgun  Offline
Joined: Jul 2006
Posts: 23
Aw! You should edit out your last sentence.

Re: Brain teaser #71327
10/26/06 05:40 PM
10/26/06 05:40 PM
Sixer  Offline
Joined: Aug 2005
Posts: 265
(the last sentence gave the clue)

I deleted my post so others can have a chance at guessing it.

[This message has been edited by Sixer (edited 10-26-2006).]

[This message has been edited by Sixer (edited 10-26-2006).]


"Will it be cheaper if I drill the holes for you?"
Re: Brain teaser #71328
10/26/06 07:18 PM
10/26/06 07:18 PM
Bob  Offline
Joined: Feb 2002
Posts: 182
Mobile, AL, USA
Turn sw#1 on and leave it on for 1 minute.
Then turn it off.
Turn on sw#2 and leave it on.
Goto attic and climb ladder.
Feel the off bulbs. The hot one is on sw#1
and the other is on sw#3.

Re: Brain teaser #71329
10/26/06 07:35 PM
10/26/06 07:35 PM
e57  Offline
Joined: May 2003
Posts: 2,876
I heard this one on Car Talk....

Mark Heller
"Well - I oughta....." -Jackie Gleason
Re: Brain teaser #71330
10/26/06 07:39 PM
10/26/06 07:39 PM
Surfinsparky  Offline
Joined: Jul 2005
Posts: 73
merritt island fl usa
Step 4 re-wire lights to one switch and locate switch near attic access!!

Re: Brain teaser #71331
10/26/06 10:31 PM
10/26/06 10:31 PM
JoeTestingEngr  Offline
Joined: Nov 2005
Posts: 791
Chicago, Il.
It was an easy solution but I started wondering how MacGyver would've done it. I'm pretty sure he would've started by taking apart the clothes dryer. He might also have left the switch on and looped a string with a weight, secured to the rafter, around the handle. The can of spray starch would act like a blow torch ,(see also: James Bond, "Live and Let Die" venomous snake application), on the string. This would create a precise, for MacGyver, time delay, allowing ample transit time to the attic. Now, if he can only help Dana Elcar grow his hair back and get him to stop picking on Pappy Boyington!

Re: Brain teaser #71332
10/27/06 01:08 PM
10/27/06 01:08 PM
Alan Belson  Offline
Joined: Mar 2005
Posts: 1,803
Mayenne N. France
One of the bulbs has been 'borrowed' by a sheetrocker: How many trips to the attic do you need to do to be 100% sure which switch operates which bulb?


Wood work but can't!
Re: Brain teaser #71333
10/27/06 01:52 PM
10/27/06 01:52 PM
Dnkldorf  Offline
Joined: Dec 2004
Posts: 1,064
nowhere usa
Make one trip up there and install a camera?

Re: Brain teaser #71334
10/27/06 04:51 PM
10/27/06 04:51 PM
wa2ise  Offline
Joined: Nov 2002
Posts: 786
Oradell NJ USA
One of the bulbs has been 'borrowed' by a sheetrocker: How many trips to the attic do you need to do to be 100% sure which switch operates which bulb?

Well, if neither of the two remaining bulbs is on, but one is warm, the missing bulb must be the one that's "on". Vefify by taking one of the two remaining bulbs to try it in the empty socket, it should light. You don't have to leave the attic. One trip

Or if one is on, and the other is warm, then the missing bulb is the one that was always off. Or if the dark bulb is cold, then the missing bulb was the one that would have been warm. One trip

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