Light Switches: Newsletter Challenge (10/18/05)

Send his apprentice up the stairs.

Assuming this is a logic problem and not an electrical one (shudder): Flip switch one ON and wait 5 mins. Flip switch two ON and wait 5 mins. Flip switch three ON and run upstairs. Coolest is switch three, hottest is switch one. Just don't burn your fingers. This is assuming they're filament bulbs; if they're incandescent, I'm to square one.

it would be as simple as one switch on, one off, then place a test lamp of equal voltage in line with the last, this would make it burn at half brilliance. thus making each light different. Evar

Assuming these are standard light fixtures: Turn on the first switch for 2-3 minutes and then turn off. Turn on the second switch and go upstairs. The light bulb that is hot to the touch is connected to the first switch, the light bulb that is off is connected to the last switch and of course the light that is on is connected to the second switch.

you have to remember this is a lazy worker.. would he want to bring a ladder up the stairs to check.... for temp change.... he would go for the least amount of work..I would think.

Poor Frank. If I am Donna Trump I will say "Frank,. You are Fired!. Well, I really have no idea.

Easy (if you apply some lateral thinking!) Frank switches on one of the lights (after noting the switch position), he then goes for a cuppa. On his return, he switches the light off and switches on another (again noting the switch position). He heads upstairs to find that one bulb is off but still warm, one bulb is illuminated, and one bulb is cold......Voila!

How about this: He turns two lights on. He goes upstairs and notes which one is off (this determines one switch – light correspondence). He removes one light from its socket, leaving the other in place, noting which light is still in its socket. He goes back downstairs. He checks the voltage at the two switches that were turned on. The one that shows no voltage across the screw terminals when the switch is turned off is the one controlling the socket with the light in place. The third is controlled by the remaining switch. QED

Frank, being Lazy.....uses his skills to hire a contractor to do the work and specifies that the swithces must be labeled!!! Just kidding, turn on two switchs for a couple of minutes, turn one off.....go upstairs, he now has one bulb on, one bulb warm and one off....answered! I didn't think of this, I was too lazy to think and used my skill to find it on the internet, maybe I'm Frank!

All the solutions that work assume that the lazy electrician had installed bulbs in the circuits. Installing light bulbs does not require an electrician's skill and a lazy electrician would probably leave it up to the home owner. So without light bulbs, he could leave one switch off, one switch closed and on the third disconnect the switched wire and short it to neutral. Then taking his trusty multimeter upstairs he would test the first socket to see if it was hot. If not he would then switch the meter to measure resistance and see if the circuit was open or shorted to neutral. He would then go to the second circuit and repeat. After checking the second, he would know which switch was connected to which circuit.

Frank is so lazy he dosn't carry tools so he slipped a nickel into one of the light sockets providing a short to the circut breaker. This gave him the third variable to the on off switches.

As written in the 10/25 issue of Specs & Techs from GlobalSpec:

"Frank" should turn Switch 1 on for a minute and then turn it off. He should then turn Switch 2 on, leave it on and go upstairs. He can assign the lights as follows:

Switch 1 is for the light bulb that is off and warm.
Switch 2 is for the bulb that is on.
Switch 3 is for the light bulb that is off and cold.

The insight comes in when one realizes that a light bulb is not merely a Boolean (which only has two possible states, on and off), but a device that has another property — heat!

Who said the light switches were down stairs? The newsletter says "all of which are upstairs" which I would think includes both the lights AND the switches.