Solve the Mystery: Identify Light Bulb Switches

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Discussion Overview

The discussion revolves around a puzzle involving three light switches and three corresponding light bulbs in an adjacent room. Participants explore various methods to identify which switch controls which bulb under specific constraints, including the inability to see the bulbs while manipulating the switches and only being allowed to enter the room once.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant suggests turning on the first switch, waiting 15 minutes, then turning it off and turning on the second switch to identify the bulbs based on their heat and whether they are lit.
  • Another participant questions the assumptions about the bulbs being heat-sunk and water-cooled, implying that this could affect the proposed solution.
  • A different participant humorously suggests using a circuit tracer to identify the wiring, indicating a more technical approach.
  • One participant proposes a method of breaking a bulb to identify which switch controls it, highlighting a more destructive approach to the problem.
  • Another participant discusses the complexity of possible wiring configurations, suggesting there could be many more combinations than initially considered.
  • Several participants provide variations on the original solution, emphasizing the use of heat to identify the bulbs, but with slight differences in the timing and methods described.

Areas of Agreement / Disagreement

There is no consensus on a single solution, as participants present multiple methods and approaches, some of which are contested or rely on different assumptions about the setup.

Contextual Notes

Participants express uncertainty about the conditions of the bulbs and the switches, including potential complexities in wiring and the physical properties of the bulbs that may affect the proposed solutions.

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You are in a room with 3 light switches. These switches are connected to 3 separate light bulbs in an ajoining room. Access to the ajoining room is via a door that remains closed, there are no windows, other people etc etc.

You are allowed to enter the ajoining room once and then return. At no time can you view the light bulbs whilst being able to manipulate the light switches.

Under these conditions, how do you identify which switch is connected to which light bulb?
 
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Need to convert the binary switches to ternary (select to see solution):


Turn switch 1 on.
Wait 15 minutes.
Turn switch 1 off - turn switch 2 on.
Run into room.
Lit bulb is controlled by switch 2.
Warm bulb is controlled by switch 1.
Cold bulb is controlled by switch 3.
[/color]
 
You did say the bulbs are heat-sunk and water-cooled, didn't you ?
 
I know it is right because that was what I was going to post. I was 18 minutes off getting it. Heck. :smile:

The Bob (2004 ©)
 
Gokul43201 said:
You did say the bulbs are heat-sunk and water-cooled, didn't you ?

No, but, unfortunately, he neglected to mention the door was locked and they gave you a key ring with 4096 keys on it. :cry:
 
My company has a circuit tracer, which can be used to trace wiring through walls...
 
Ah BobG, so you whipped out the mini hatchet from your 117-tool Swiss Army Knife (you know, the new one ...that comes with a little slide-rule), and tore down the door ? Or did you go for the micro-battering-ram ?
 
Hey russ, I've got one of those too. I call it my multimeter with reeeeaaaalllly long leads.

No ? Not that one, eh ?
 
:cry: Rats, that was either too easy or you saw it before
 
  • #10
You could also flick one on and off for a long long time until it breaks the filament. Then turn another on and go see which is which. The broken filament one will have a discoloration and ringing when shooken.
 
  • #11
Need more info.

So, you've got three switches, and three light bulbs.

Each switch can be set up to toggle each of the three light bulbs, so that's 8 possible set up's per switch, for a total of at least 512 possible wirings (and that's without getting tricky...). Now, if we go into the room there are at most 8 possible results.
If you want to get tricky, there are 8!=40320 possible wiring arrangements that insure that all lighting combinations are possible, and for sufficiently creative electricians there are 8^8=16777216 possible wiring combinations.

Even using BobG's clever ternary technique, there are at most 27 possible states for the light bulbs in the room.
 
  • #12
NateTG said:
Even using BobG's clever ternary technique, there are at most 27 possible states for the light bulbs in the room.

There maybe 27 different places where they can be but only one (or two ways) to solve the problem.

The Bob (2004 ©)
 
  • #13
this is utterly easy. pull one light switch completely as in pull out of wall, turn on one light and go look. the one with the busted bulb will be connected to the switch that was yanked out, easy :smile:
 
  • #14
Solution...but this problem doesn't belong HERE.

I believe this is an easy one...probably too easy for this forum, but here goes:

If there are three switches in one room and you cannot directly see the results when you turn a switch, then you must rely on other senses to determine which switches coordinate with which light bulb. To facilitate that, you turn on one switch for about 5 minutes and wait. At the end of 5 minutes, you turn that first switch off and turn another one on. Then you proceed into the room containing the light bulbs. One of the light bulbs will be lit corresponding to the switch that is currently on. Of the two remaining light bulbs that are not lit, you must touch them to determine which is heated from being left on for a 5 minutes. The hot one is the one corresponding to the first switch you operated.

So, in a nutshell, when one physical sense is neutralized, rely on another for its input.

"God, in infinite wisdom, made all things simple. Man made them complex."
 
  • #15
What you do is you turn one light on, wait half an hour, turn on another light then go in the room and see witch bulb is hotter. The hotter bulb is the one you turned on first, the less hot lit bulb is the one you turned on second and the unlit bulb it the third switch
 

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