In front of you are three light switches. Only one does anything, and it turns on the light downstairs. From here you can't see the light, and it makes no sound. You must determine which switch operates the light, BUT you can only go check it once. How do you figure out which switch is for the light?

Flip any switch you want. Wait for about 5-10 minutes to let the bulb heat up. Flip that same switch off, and another one on. Go check the light. If it's off and hot, it was the first switch, if it's on it was the second and if it's cold and off, it was the last one.

Flip the switch on one end, wait a "long" time (e.g., 15 minutes); then flip the middle switch; them immediately go check the light for on/off status and temperature. If off: the switch you didn't change controls the light; If on and surrounding fixtures slightly warm, the middle switch controls the light; If on and surrounding fixtures fully warm of hot, the first switch controls the light.

Tell the HR interviewer to go stick his/her finger in the light socket and scream when you flip the correct switch.

I frankly enjoy all the wry responses! Because this is just one of many ridiculously shallow and pointless interview questions that reveals much more about the intent and competence of the interviewer rather than the interviewee. Preparing for and sitting through an interview is tense enough - so it is totally deflating when a "gotcha" question like this is thrown at you. When I hear a question like this during an interview, I immediately know that the interviewer is 1) incredibly lazy and 2) clueless about how to actually gather worthwhile information in order to make an informed decision. Is that person someone you would want working with/supervising you???

The first answer is right of course. Most of the other answers would make the interviewer realize you don't listen, don't understand the question, or don't care. Either way, not what you want in an interview. Don't jerk around.

Use solution one. Then use the light to get out - unless downstairs is the switch to fire the HR Department. I do like the use "an electrical tester" answer - unless you're interviewing for a safety job.

You have no way of knowing which switch controls the light. The "correct" answers above assume the light is initially off. If the light started out as on and you performed this test you would get misleading results.

The "temperature" method is clever but that assumes the lights are incandescent and you're close enough to the bulbs that you can get there before they cool down to room temperature. An interviewer might look at that answer as clever but wrong because you make assumptions that weren't explicitly allowed (Microsoft would probably say this). My answer would either be. a) Ask for help (shows you not afraid to be a team player b) Do it the electrical engineering way and put a video camera in the room and wait 15 minutes before flipping each switch. It's really a stupid question though that says nothing about how good of an employee you'll be.

Use solution one. Then use the light to get out - unless downstairs is the switch to fire the HR Department. I do like the use "an electrical tester" answer - unless you're interviewing for a safety job.

oops! can only check it once. I dont get the job because I cant follow directions...If i'm in charge of the project, I can check it as many times as I like!!!

Take the faceplate off and look inside to see which switch has wires hooked to it. That would be the winner.

I would either ask someone on the team who already knows which light switch it is or I would search the Internet for the solution to figuring it out on my own.

It does not have sense because I am not an electrician. So I can flip any switch, after few minutes flip once again this switch and any other and go check to bulb. If it will be dark I can not check anything because I can not find the bulb I it will be light it does not mater which switch operate. I can go forward, :)

subduejoy clearly has the answer, it's what I do for most of my problems.

I'll take the job. I can think of several solutions. I like these questions. And they are not pointless. How you answer such a question, or how you attempt to do it shows ho imaginative you are and whether you persist. A few possible solutions: 1. If it is dark outside, or the building does not have windows, operate the switches one at a time until you hear angry voices from downstairs - nobody likes to stay in the dark. 2. Otherwise, operate the switches one at a time and ask the people downstairs. 3. Do not operate any switch. Take your light-detecting sensor downstairs. The sensor transmits a wireless signal to the receiver in your pocket. Get back to the panel and start flipping the switches until you get the signal from the receiver. 4. Take your bow and three arrows with dull heads (you do not want to damage the switches). Go to a place from where you can see both downstairs and the panel. Start flipping the switches one by one by shooting arrows at them. 5. You need a big fly - one of those you can hear flying. Turn off all the lights in the building. The lights must be on only at the place where you stand and downstairs. Have someone release the fly downstairs - you can hear it buzz. Start flipping the switches one a time and wait. You know you got the right switch when you stop hearing the fly (or when it comes to you).

Ask someone to go downstairs and yell up to you when it works. What are you people mentally challenged?

I like the answer about requesting someone to go downstairs and check the light while you flip the switch, it shows 3 things about you: #1-You're not afraid to ask for help when needed. #2- It shows you can delegate. These responses coincide with TEAMWORK. Unless the interviewer has specifics, in which you ask. That could be the #3rd answer-BEING RESOURCEFUL by asking questions. It shows your interest in the job and you don't have to be an electrician to figure it out.

1. Flip one switch 2. wait 2 minutes 3. Flip switch off again 4. Flip another switch on 5. Immediately go downstairs and check if a light is on If the light is off, the switch you flipped in step 4 is not correct. 6. Touch the bulb If the bulb is cold, the switch you flipped in step 1 is incorrect. That means that the remaining switch is the correct choice. If the bulb is hot, the switch you flipped in step 1 is the correct choice.

send your helper downstairs to let you know when the light turns on and off.

Collins has the answer - Flip all 3 switches

LOL...good luck tripping and stumbling while looking for the warm light bulb in the dark! Turn all three switches on. The flip one switch off at a time and check to see if the light goes off after flipping that switch off. When the light goes off...that was the switch.

Open the switch plate, using an electrical tester- test for the live wire. Only one will test positive.

flip them all on. only one does anything so the other two really doesn't mean anything.

On a multiple unit switch the farthest left is often the first to be hooked up,

Flip switches, keep checking, at the foor of the stairs, until you see light; that will be the switch!