The Electrical Contractor Network

ECN Electrical Forum
Discussion Forums for Electricians, Inspectors and Related Professionals

Books, Tools and Test Equipment for Electrical and Construction Trades

Register Now!

Register Now!

We want your input!


2017 NEC and Related
2017 NEC
Now Available!

Recent Posts
Son of Sparky
by HotLine1
10/20/16 07:43 PM
Speaking of Plugmold ...
by gfretwell
10/17/16 02:37 PM
Broken battery charger? Check for cobwebs!
by gfretwell
10/17/16 02:30 PM
230 or 345 kV transmission lines?
by annemarie1
10/12/16 01:23 PM
Is this a fix or just a bandaid?
by gfretwell
10/10/16 06:49 PM
New in the Gallery:
12.5A through 0.75mm˛ flex (just out of curiosity)
Shout Box

Top Posters (30 Days)
gfretwell 11
renosteinke 6
HotLine1 6
ghost307 5
sparky 4
Who's Online
1 registered (annemarie1), 302 Guests and 5 Spiders online.
Key: Admin, Global Mod, Mod
Page 1 of 2 1 2 >
Topic Options
Rate This Topic
#71325 - 10/26/06 02:16 PM Brain teaser
Rewired Offline

Registered: 01/01/06
Posts: 567
Loc: Hamilton, Ontario, Canada
This one was told to me by a plumber today at the jobsite. Its easy I figured it out

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

Work Gear for Electricians and the Trades
Work Gear for Electricians and the Trades
Arc Flash Clothing, Gloves, KneePads, Tool Belts, Pouches, Tool Carriers, etc. etc....

#71326 - 10/26/06 02:33 PM Re: Brain teaser
rabbitgun Offline

Registered: 07/25/06
Posts: 21
Aw! You should edit out your last sentence.

#71327 - 10/26/06 02:40 PM Re: Brain teaser
Sixer Offline

Registered: 08/08/05
Posts: 264
Loc: Canada
(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 04:18 PM Re: Brain teaser
Bob Offline

Registered: 02/05/02
Posts: 182
Loc: 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 04:35 PM Re: Brain teaser
e57 Offline

Registered: 05/27/03
Posts: 2837
Loc: S.F.,CA USA
I heard this one on Car Talk....
Mark Heller
"Well - I oughta....." -Jackie Gleason

#71330 - 10/26/06 04:39 PM Re: Brain teaser
Surfinsparky Offline

Registered: 07/29/05
Posts: 77
Loc: merritt island fl usa
Step 4 re-wire lights to one switch and locate switch near attic access!!

#71331 - 10/26/06 07:31 PM Re: Brain teaser
JoeTestingEngr Offline

Registered: 11/04/05
Posts: 786
Loc: 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 10:08 AM Re: Brain teaser
Alan Belson Offline

Registered: 03/23/05
Posts: 1801
Loc: 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 10:52 AM Re: Brain teaser
Dnkldorf Offline

Registered: 12/12/04
Posts: 1091
Loc: nowhere usa
Make one trip up there and install a camera?

#71334 - 10/27/06 01:51 PM Re: Brain teaser
wa2ise Offline

Registered: 11/29/02
Posts: 769
Loc: 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 >

ECN Electrical Forums - sponsored by Electrical Contractor Network - Electrical and Code Related Discussion for Electrical Contractors, Electricians, Inspectors, Instructors, Engineers and other related Professionals