In your cellar there are three light switches in the OFF position. Each switch controls 1 of 3 light bulbs on the floor above. You may move any of the switches, but you may only go upstairs to inspect the bulbs one time. How can you determine the switch for each bulb with one inspection?

Question

Physics

Gerardo Christensen

20 March, 07:06

In your cellar there are three light switches in the OFF position. Each switch controls 1 of 3 light bulbs on the floor above. You may move any of the switches, but you may only go upstairs to inspect the bulbs one time. How can you determine the switch for each bulb with one inspection?

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Answers (2)

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Rhianna · Answer 1

Number the switches 1, 2 and 3.

Switch on number 1 for 1 minute, then switch it off. Switch on number 2. Go upstairs ...

The light that is on is connected to switch 2. The light that is off and warm is connected to switch 1. The light that is off and cold is connected to switch 3!

Dylan Murphy · Answer 2

We have three switches 1, 2 and 3.

Firstly, switch on the first switch for like 2mins, then switch of the first switch and switch on the second switch, then rush immediately up stars, if the bulb is on,

Then it is between switch 1 and 2, so feel the bulb immediately, if the bulb is hot, it show that it was switch 1 due to the heat the but has emitted over the long period of time, but if it is still cold and just about to be getting warm, then it is the second switch.

Second case, if the bulb was off when you get upstairs, this shows that it, it is between switch 1 and 3.

Now, feel the bulb, it is hot then, it is switch 1 due to the heat. but if it is cold then it is switch 3 because none of the switch was able to power on the bulb