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Topic: 5 light bulbs (Read 710 times) |
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alien2
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5 light bulbs
« on: Aug 11th, 2007, 11:23am » |
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This riddle is a similar version of the 3 light bulbs riddle, and everything is the same, except for the fact that there are 5 light bulbs and 5 switches. 
Just in case someone isn't familiar with the riddle, here is the link of a recent one.
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Grimbal
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Re: 5 light bulbs
« Reply #1 on: Aug 11th, 2007, 2:50pm » |
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Same as here except of course that you have 5 switches and 5 light bulbs.
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mikedagr8
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Re: 5 light bulbs
« Reply #2 on: Aug 11th, 2007, 4:37pm » |
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I'm going to wait for an actual answer, then hopefull with the correct timing, proclaim it as my own. Unless we are assuming the links contain the answers. 
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JiNbOtAk
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Re: 5 light bulbs
« Reply #3 on: Aug 12th, 2007, 5:57pm » |
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Of course, with precise measurement, Grimby's solution could be used for a large number of bulbs and switches.
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Sameer
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Re: 5 light bulbs
« Reply #4 on: Aug 12th, 2007, 6:29pm » |
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or blow out fuse of one of the bulbs by repeatedly turning one switch on/off and then use the 4 bulb method for the remaining!!!
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"Obvious" is the most dangerous word in mathematics.
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Proof is an idol before which the mathematician tortures himself.
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mikedagr8
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Re: 5 light bulbs
« Reply #5 on: Aug 12th, 2007, 11:25pm » |
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That's what i was thinking. 
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alien2
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Re: 5 light bulbs
« Reply #6 on: Aug 14th, 2007, 6:17am » |
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I'm not going to comment yet. But when I do, I will say everything, so you better hurry up if you have something to add. Regardless, I will give a clue, regarding figuring out one switch: you touch two bulbs, and their temperature feels the same. Still, can you figure out which bulb belongs to which switch? Btw, please disregard Sameer's idea. 
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Sameer
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Re: 5 light bulbs
« Reply #7 on: Aug 14th, 2007, 8:27am » |
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on Aug 14th, 2007, 6:17am, Iceman wrote:| Btw, please disregard Sameer's idea. |
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"Obvious" is the most dangerous word in mathematics.
--Bell, Eric Temple
Proof is an idol before which the mathematician tortures himself.
Sir Arthur Eddington, quoted in Bridges to Infinity
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alien2
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Re: 5 light bulbs
« Reply #8 on: Aug 14th, 2007, 10:23am » |
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I thought that fuse is something else. But now that I know what it is, there are still no fuses at your disposal, buddy. But if there were, are you right for sure? I dunno much about fuses. Perhaps we need an electrician here.
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| « Last Edit: Aug 14th, 2007, 1:53pm by alien2 » |
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denis
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Re: 5 light bulbs
« Reply #9 on: Aug 14th, 2007, 12:38pm » |
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Use dimmer switches which can gradually increase and decrease light intensity of each bulb. In this case, you need not use temperature as your measurement.
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Sameer
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Re: 5 light bulbs
« Reply #10 on: Aug 14th, 2007, 12:43pm » |
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on Aug 14th, 2007, 10:23am, Iceman wrote:| I thought that fuse is something else. But now that I know what it is, there are still no fuses on your disposal, buddy. But if there were, are you right for sure? I dunno much about fuses. Perhaps we need an electrician here. |
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Alrite I meant fuse as the tungsten wire in the bulb. When switch is repeatedly turn on/off the current surge may melt the tungsten wire and "blow its fuse" ... haven't you blown out bulbs like this when you were a kid?
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"Obvious" is the most dangerous word in mathematics.
--Bell, Eric Temple
Proof is an idol before which the mathematician tortures himself.
Sir Arthur Eddington, quoted in Bridges to Infinity
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alien2
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Re: 5 light bulbs
« Reply #11 on: Aug 14th, 2007, 2:00pm » |
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No. Never tried it, and never will. I'm not a kid no more. But if you're right, you're right. And I suppose you are talking about coiled-coil filament? It is within the glass bulb.
on Aug 14th, 2007, 12:38pm, denis wrote:| Use dimmer switches which can gradually increase and decrease light intensity of each bulb. In this case, you need not use temperature as your measurement. |
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That would be convenient for sure. Alas, no such switches, just usual ones.
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Sameer
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Re: 5 light bulbs
« Reply #12 on: Aug 14th, 2007, 3:51pm » |
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on Aug 14th, 2007, 2:00pm, Iceman wrote:No. Never tried it, and never will. I'm not a kid no more. But if you're right, you're right. And I suppose you are talking about coiled-coil filament? It is within the glass bulb.
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Correct, it is made of tungsten!!! At least most of it is... haven't kept up with bulb technology ...
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"Obvious" is the most dangerous word in mathematics.
--Bell, Eric Temple
Proof is an idol before which the mathematician tortures himself.
Sir Arthur Eddington, quoted in Bridges to Infinity
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alien2
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Re: 5 light bulbs
« Reply #13 on: Aug 14th, 2007, 4:45pm » |
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Me neither.
As I said, I won't comment yet, except for the fact that Grimbal has opened the doors of bulbs and switches wide open! I thought that I have done that, but I was wrong. That is his original idea. Still, if we disregard his fine idea, just for a moment, of course, how would you solve the riddle then? Including denis' idea for the 4 bulbs riddle, which isn't bad, one could provide a solution for 6 light bulbs and 6 switches riddle! W/o Grimbal's idea, of course. 
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alien2
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Re: 5 light bulbs
« Reply #14 on: Aug 14th, 2007, 4:48pm » |
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Then again, what I have in mind is not that different either. As you most probably know by now, timing is important here. So best thing for you is to play at home with a light bulb, and remember times well.
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alien2
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Re: 5 light bulbs
« Reply #15 on: Aug 15th, 2007, 4:34am » |
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Personally, I think that 1st version, well known 3 light bulbs riddle, is still the best, meaning the most correct, w/o additional tangles. Still, it won't hurt to explore new horizons, will it?
Btw, there is another thing that could improve Grimbal's idea.
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Grimbal
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Re: 5 light bulbs
« Reply #16 on: Aug 15th, 2007, 5:33am » |
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on Aug 15th, 2007, 4:34am, Iceman wrote:| Btw, there is another thing that could improve Grimbal's idea. |
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Well, yes, you could have half the bulbs off and cooling, and the other half on and getting hot (hopefully slowly).
But to say that it is an improvement would imply it could be difficult to differentiate the temperature, so that possibly 5 bulbs could be already too much for the method. Being mathematically minded, I consider I know that an inverse exponential is strictly decreasing, however small the difference in time is. That's why I did not bother giving that solution.
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denis
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Re: 5 light bulbs
« Reply #17 on: Aug 15th, 2007, 7:09am » |
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on Aug 14th, 2007, 6:17am, Iceman wrote:| regarding figuring out one switch: you touch two bulbs, and their temperature feels the same. Still, can you figure out which bulb belongs to which switch? |
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Take out the bulb and feel the base where it screws in. The one that was turned on longer (or turned off for a shorter period) will be noticeably warmer there because the heat will have had more time to reach this area (or less time to cool off).
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| « Last Edit: Aug 15th, 2007, 7:11am by denis » |
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alien2
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Re: 5 light bulbs
« Reply #18 on: Aug 15th, 2007, 7:26am » |
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on Aug 15th, 2007, 7:09am, denis wrote:
Take out the bulb and feel the base where it screws in. The one that was turned on longer (or turned off for a shorter period) will be noticeably warmer there because the heat will have had more time to reach this area (or less time to cool off). |
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Yes, this idea can improve Grimbal's, for screw base is out of metal, meaning that it cools slower than glass bulb. So when the glass bulb cools entirely, you enter the room, and you can still figure out which light bulb, out of two cool glass bulbs, belongs to which switch. Eureka! So, you could apply Grimbal's method to more cool glass bulbs than two, as bulb's screw bases have different temperatures.
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denis
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Re: 5 light bulbs
« Reply #19 on: Aug 15th, 2007, 7:35am » |
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on Aug 15th, 2007, 7:26am, Iceman wrote:
Yes, this idea can improve Grimbal's, for screw base is out of metal, meaning that it cools slower than glass bulb. |
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Well actually, the reason has more to do with the fact that the base is further away from the filament (which is the heat source) and the bulb is closer.
It turns out that metal is a heat conductor and does cool and heat faster than glass under the same conditions. However, because there is more metal at the point where it screws in, there is a heat sink there and it is not exposed to the air like the bulb is so it cannot shed the heat by convection. It can only shed the heat by conduction therefore it heats up and cools down more slowly than the bulb.
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| « Last Edit: Aug 15th, 2007, 7:45am by denis » |
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alien2
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Re: 5 light bulbs
« Reply #20 on: Aug 15th, 2007, 7:58am » |
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Have it your way, Mr Perfect.  Regardless, we are dynamic duo. When we put our heads together, nobody can stop us.
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