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Re: Brainteaser

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lsmith(--nospam--at) wrote:
> OK, this has nothing to do with engineering, but you do need to think to
> figure it out, so, I believe we all qualify.  According to a friend of
> mine, this was a question from a MENSA test:
> There is a switchplate with three (3) switches in the basement of a house.
> Up the stairs in a room on the ground floor is a light bulb.  The new owner
> of the house knows that the light bulb is controlled by one of the three
> switches and is in the basement.  With only one trip up the stairs, how can
> the new owner determine which switch controls the light bulb?
Can you give us some more criteria, such as;
1.	Can the light bulb be moved to the basement while it is still
controlled by the switch?
2.	Can the light emitted from the light bulb (assuming, of course, that
the control which the switch has over the light is the switch's abitlity
to either allow electrical power to flow to, or to prevent that same
electrical current from flowing through, that light bulb, thereby
causing the light bulb to emit light rays) been seen from the basement
if the basement door (if any) is left open?
3.	Is the new owner the one who is limited to one trip up the stairs? 
If so, can the new owner enlist helpers who are not limited in the
number of trips which they can take up and down the stairs?  (Sometimes
what appears to be an engineering problem is really just a matter of
applying what we should have learned in kindergarten -- cooperative
4.	Does the new Owner have access to a voltage meter?
5.	Can the new Owner use jumpers from the light bulb's socket (assuming,
of course, that the light bulb is connected to a socket which is wired
to at least one of the switches in subject bank of switches) to set up a
remote device to indicate, in the basement, flow of electrical current
through the bulb's socket?
6.	If no to 5, above, can the new Owner use jumpers from the switches to
open and close the switch legs in view of the light bulb?
7.	Is there alternate access from the basement to the room containing
subject light bulb so that access can be had without going up the
8.	Is there a video monitor, or any other type of monitor, which could
communicate to the new owner, while in the basement, when a switch is
successful in operating the light?
9.	Is subject new owner certain that the bulb operates with current
applied across it (i.e., are the contacts still conductive, is the
filament intact, etc.)?