ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Top Posters(30 Days)
Potseal 11
Recent Posts
600 KW 120/208 3 Phase Y protection
by Yooperup. 07/24/17 12:20 PM
1913 American Electrician's Handbook
by gfretwell. 07/20/17 01:08 PM
Green House wiring
by ghost307. 07/20/17 09:10 AM
Permit Snafus...AHJs and Contractors Jump in
by HotLine1. 07/18/17 08:06 PM
New in the Gallery:
SE cable question
Popular Topics(Views)
239,330 Are you busy
174,797 Re: Forum
167,170 Need opinion
Who's Online Now
0 registered members (), 81 guests, and 10 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate This Thread
Page 1 of 2 1 2
#71325 - 10/26/06 05:16 PM Brain teaser  
Rewired  Offline
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

#71326 - 10/26/06 05:33 PM Re: Brain teaser  
rabbitgun  Offline
Joined: Jul 2006
Posts: 23
Aw! You should edit out your last sentence.

#71327 - 10/26/06 05:40 PM Re: Brain teaser  
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?"

#71328 - 10/26/06 07:18 PM Re: Brain teaser  
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.

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

Mark Heller
"Well - I oughta....." -Jackie Gleason

#71330 - 10/26/06 07:39 PM Re: Brain teaser  
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!!

#71331 - 10/26/06 10:31 PM Re: Brain teaser  
JoeTestingEngr  Offline
Joined: Nov 2005
Posts: 785
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!

#71332 - 10/27/06 01:08 PM Re: Brain teaser  
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!

#71333 - 10/27/06 01:52 PM Re: Brain teaser  
Dnkldorf  Offline
Joined: Dec 2004
Posts: 1,064
nowhere usa
Make one trip up there and install a camera?

#71334 - 10/27/06 04:51 PM Re: Brain teaser  
wa2ise  Offline
Joined: Nov 2002
Posts: 782
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

Page 1 of 2 1 2

Member Spotlight
Anaheim, CA. USA
Posts: 2,707
Joined: October 2000
Show All Member Profiles 

2017 NEC and Related
2017 NEC
Now Available!

Shout Box
Powered by UBB.threads™ PHP Forum Software 7.6.0
Page Time: 0.015s Queries: 15 (0.002s) Memory: 0.8170 MB (Peak: 0.9927 MB) Zlib enabled. Server Time: 2017-07-25 16:53:48 UTC