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The Box
Posted: Thu Apr 25, 2013 10:28 am
by Saint_
A light bulb is placed in a solid metal box with a lid. The lid is switched so that if it is opened, the light goes off instantly.
There are two switches on the outside of the box. One lights the light, the other does nothing.
How can you tell which switch is the working one?
The Box
Posted: Thu Apr 25, 2013 10:31 am
by Oscar Namechange
Open the lid ?
The Box
Posted: Thu Apr 25, 2013 10:33 am
by YZGI
Turn one on then open box and see if the light is warm. If not it's the other switch?
The Box
Posted: Thu Apr 25, 2013 10:42 am
by Saint_
YZGI;1425327 wrote: Turn one on then open box and see if the light is warm. If not it's the other switch?
We have a winner! That was fast.
The Box
Posted: Thu Apr 25, 2013 12:16 pm
by Bruv
You could always drill a small hole and close the lid in a darkened room...................but why bother...... there is no need for a light in an empty box anyway:-2
The Box
Posted: Thu Apr 25, 2013 1:30 pm
by tude dog
Saint_;1425328 wrote: We have a winner! That was fast.
Yea, that was clever, I liked it.
Only thing I came up with was checking the switches with a volt meter, though I knew that wasn't really in the spirit of the question.
The Box
Posted: Thu Apr 25, 2013 1:31 pm
by tude dog
Bruv;1425330 wrote: You could always drill a small hole and close the lid in a darkened room...................but why bother...... there is no need for a light in an empty box anyway:-2
Yea, thanks for that. There is always one in the crowd.
The Box
Posted: Thu Apr 25, 2013 5:16 pm
by Scrat
You probably could also use dust or metal filings. If the light is on in the box there is current flow which create lines of force. Put the material around the switch and see what it does. I don't have the means to test the theory but I'd bet it would work in some form. There would also be a temperature difference most likely but it may not be sensible with touch.
I'd just open the box and check the bulb.
