Wikipedia:Reference desk/Archives/Miscellaneous/2014 July 29

Welcome to the Wikipedia Miscellaneous Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

July 29

Laptop giving sustained electric shocks/vibrations

I recently moved to a new, basement apartment and noticed that whenever my aluminum-bodied laptop (non-macbook) is plugged int the AC outlet, I can feel electric vibrations whenever I gently slide my hand over the aluminum palmrest. Occasionally, I also feel sustained sharp electric shocks.

Looking online, it seems like this phenomenon happens when plugging the computer into a ungrounded outlet. However, the outlet in this basement is three-pronged and does appear to be grounded.

What could be causing this? Could it mean that the AC outlet in the wall is, in fact, NOT grounded properly?

Are there any long-term dangers to myself or my equipment?

Thanks. Acceptable (talk) 01:45, 29 July 2014 (UTC)

It's certainly possible. One of the outlets in my house had a disconnected ground wire - it was spotted during the survey we had done when we bought the place. It's somewhat dangerous for it to be disconnected...for appliances that are not faulty, it generally doesn't do anything - but, as you've discovered, if you have a short inside the metal case of an appliance, the earth connection protects you from a potentially lethal electric shock. So you should certainly get the laptop fixed - and have someone check out that outlet. There is a gizmo on sale at most DIY stores that you can plug into an electrical outlet that has a bunch of LED's on it to show whether the outlet is mis-wired and how. I checked through the entire house and found two more bad ones! I fixed them myself - it's not that difficult - but for chrissakes, make sure you turn off the power to the entire house before you try it...where there is one wiring error, there could be many more - so trust nothing! SteveBaker (talk) 04:55, 29 July 2014 (UTC)

Call your apartment's maintenance department and report the issue, adding that you suspect the outlet isn't properly grounded. They likely have the tester Steve mentioned, or know how to check it with a multimeter, and should be able to fix it easily unless it is a larger-scale problem with the unit. I would also be concerned that there is an internal fault in your laptop. The ground is a precaution in case a fault starts leaking current to the metal body, but in normal operation it shouldn't be leaking at all and the neutral line should handle the entire return current. Katie R (talk) 12:51, 29 July 2014 (UTC)

Heh, shows what I get for skimming the previous response - Steve already mentioned the fault in your laptop. Katie R (talk) 13:00, 29 July 2014 (UTC)

(edit conflict) It could also be a problem with that entire circuit - the grounds are all connected together, but not actually grounded. Or possibly the building's grounding rod has failed, or many other potential ground issues. In those cases it could be something else that shares the ungrounded ground connection leaking current, and you're picking it up through the non-faulty laptop. In any case, the management of your apartment should be able to track down the issue. If it turns out that the problem affects more than just that outlet, you may need to figure out which device on the circuit has the fault. A simple, but not foolproof, method of testing small things is to plug them into the GFCI outlet in your bathroom and see if it trips. Katie R (talk) 13:13, 29 July 2014 (UTC)

You can add your own ground until the electrician arrives. Connect a wire from the ground plug to something grounded, like a water pipe where it comes into the house. They sell adapters specifically made for this, that have a place to attach a grounding wire.

As for the vibration, it might be picking up that from something nearby, like a running washing machine. I have a metal goose neck lamp that picks up vibrations from the big screen TV and seems very much like what you described in your laptop. Apparently humans aren't good at distinguishing small vibrations from small electrical shocks. So, you may only feel vibrations, not a shock. Being made of metal seems to make vibrations worse, as other materials tend to absorb vibrational energy and convert it into heat, while metal just transmits it on. StuRat (talk) 13:07, 29 July 2014 (UTC)

Stu, your suggestion to run a new ground wire to a water pipe is not a good idea. It violates electrical safety codes. One problem is that the impedance of a faulted circuit would be higher if the return path for fault current followed a different route than the supply current, since there is less impedance when the phase and ground conductors are adjacent than when the ground goes in a different direction. I wonder if the ground prong even enters into the problem, since on my laptop the AC adapter only has 2 prongs, phase and neutral. I know the phenomenon of AC leakage giving an appliance case a certain feeling when you run your finger along it. If you were better grounded you might get a serious shock. There is generally good isolation between the mains and the wires to the appliance within the adapter, so it might be faulted, with a stray connection between the mains side and the appliance side. The outlet might have the hot (phase) and neutral leads switched from what they are supposed to be, although as I said the mains should be isolated in the adapter from the wires going to the computer. Edison (talk) 13:45, 29 July 2014 (UTC)

Your laptop is likely in a plastic chassis. UL requires devices with a conductive case to be double-insulated or have a ground connection. In the smaller/thinner/lighter is better world of laptops that means a ground connection is the best option. Katie R (talk) 14:20, 29 July 2014 (UTC)

I am almost certain that these vibrations are the result of the aforementioned electric problem and not mechanical vibrations from nearby. When I switch to a different AC outlet in the apartment, this problem goes away.

This is happening on two of my aluminum bodied PC laptops and on my friend's aluminum bodies Macbook, so I'm not sure if it's faulty wiring inside the laptops. Acceptable (talk) 18:51, 29 July 2014 (UTC)

That's good to know, now stop touching it. :-P Your apartment management should be able to have someone check it out for you, it is certainly a big safety risk. There is a good chance that the only reason you haven't been shocked worse is because you weren't in direct contact with a good ground yourself. Katie R (talk) 19:51, 29 July 2014 (UTC)

What you have detected is almost certainly not a fault, but a normal leakage current of a few micro-amps which is very common and is not at all dangerous. I've been detecting this for over 50 years, and was puzzled by it until I read the Wikipedia article on Electrovibration. Of course, you should check that the current is not in the milliamp range (or even hundreds of micro-amps) because this would indicate a possible fault developing in the power supply to the laptop. Dbfirs 20:55, 29 July 2014 (UTC)

The bad ground on the outlet is dangerous. If a fault develops in something plugged into it then the entire chassis will be live. I'm skeptical on the electrovibration idea because it requires an insulating layer, but even if that is what the OP felt it shouldn't happen with a proper ground. Katie R (talk) 13:23, 30 July 2014 (UTC)

Doe the plug-in adapter in question actually have a third (ground) plug, or does it just have the two prongs? Has the one offending outlet been checked to see if the phase and neutral holes are switched? Edison (talk) 15:38, 30 July 2014 (UTC)

The plug-in adapter (the power brick of my laptop right?) does have 3-prongs. It's a fairly normal looking Dell AC adapter. The AC outlet in the wall also has 3-prongs. Acceptable (talk) 16:07, 30 July 2014 (UTC)

Most laptop bricks are double-insulated, not earthed, here in the UK. Katie is sceptical about electrovibration, but I've observed it on many unearthed appliances, and it is especially noticeable in a damp atmosphere. The Wikipedia article is misleading: the sensation is felt when dragging a finger over conducting surfaces where the leakage current is too small to be detected by nerve cells (and therefore not dangerous). Research on the exact mechanism is on-going, but I think the capacitative explanation that requires an insulating layer has been discounted. It's certainly worth checking the earth connection on the outlet, or getting an electrician to check it, just for your peace of mind (and Katie's), but if your power brick is the same as those some in the UK, then there is no ground connection, so the problem cannot lie there. If you happen to know anyone who could check the size of the leakage current, then this would determine whether or not there is a real fault. The "sharp electric shocks" are certainly not electrovibration, and possibly indicate that the circuitry inside the power brick is breaking down. If you are getting these, then I suggest that you stop using both the equipment and the outlet until you get things checked. Dbfirs 16:43, 30 July 2014 (UTC)

My understanding is that with a conductive laptop body UL requires the laptop itself to be grounded, which will happen through the power supply. Otherwise an internal fault inside the (normally isolated) brick could lead to a live voltage on the surface of the laptop. The laptop itself would have to be double-insulated to meet UL requirements without a ground connection. I just found this post [1] which explains the source of the voltage behind the tingly sensation pretty well. This is likely harmless, but it still indicates a problem with the outlet's ground connection which should be fixed. Katie R (talk) 17:27, 30 July 2014 (UTC)

Yes, I think you are correct that a laptop with a conductive body requires one pole of the output from the brick to be grounded. Thus both the electrovibration and the more serious "tingly sensation" must be caused by either using the wrong (unearthed) power supply or by a faulty earth at the outlet or in the connection to the brick. I agree that it should be fixed. Dbfirs 18:04, 30 July 2014 (UTC)

The issue of people sensing electricity when touching an Apple Mac with a metal case has been discussed on an Apple forum at https://discussions.apple.com/message/19000831#19000831 They do no apear to carry a ground connector from a power adapter to the shell of the laptop. I tested my MacBook with a Fluke 187 digital voltmeter. The Apple power adapter just has a 2 prong plug. It sends DC to the laptop. The plug has 2 equal prongs, so it goes in the 120 v outlet either way. With one voltmeter lead grounded to the outlet ground and the other just held in the air, it shows about 4 volts, due to induction, or stray capacitively coupled electricity. (The voltmeter has a high input impedance, unlike analog meters, so it picks up stray voltages.} I previously tested the computer metal shell for conductivity, and found that it has a coating (anodized?) that pretty well insulates it. unless it is scratched. I was able to find continuity between the screws on the bottom which attach the metal shell, since they would not be insulated from the shell. So I checked for voltage from those metal screws attached to the metal shell, to the ground, and detected 53 volts. I could not feel any tingle from the voltage, although a current check showed it to supply 0.15 milliampere when shorted to ground via the meter. Do not try this at home, since it is easy to forget and connect the ampere function across the 120 power, or there might be a low impedance short from a hot lead to something, causing injury or equipment damage. Electric shock says people can feel 1 milliampere of AV Highvoltageconnection.com reports that 60 Hz AC can be detected by some people as low as 0.3 ma, not far above what I measured. I reversed the power adapter in the power socket, and the voltage on the case dropped to 1.4 volts and the available current was only 2 microamperes. I expect that there is some capacitive coupling of AC to the lwires which go to the computer and thence to the laptop shell, and that the shell is more closely coupled to one prong of the power plug than the other prong. If one outlet causes the problem and others don't then the outlets might differ in where the hot and neutral are connected. Edison (talk) 19:48, 1 August 2014 (UTC)

Black Kettle Argument ?

I just read an argument written by a politician. He is criticizing an opponent. His critique against the opponent is this: They are criticizing their opponent.

This reminds me of "calling the kettle black".

I tried to categorize this argument with the help of List_of_fallacies but did not manage to find a good fit.

I do not want to force the argument into any category. It has to be a perfect fit, or it would not seem valid to me. I am not in the habit of doing original research anymore, but I am attracted to the idea of inventing the term "black kettle" argument.

Perhaps I have misjudged it, and it is not an argument fallacy after all? Star Lord - 星王 (talk) 10:09, 29 July 2014 (UTC)

Could it categorized as a special form of reflective ad hominem argument? Star Lord - 星王 (talk) 10:29, 29 July 2014 (UTC)

Or one could call it a boomerang argument :) Star Lord - 星王 (talk) 10:31, 29 July 2014 (UTC)

Wikipedia has an article titled The pot calling the kettle black. --Jayron32 12:34, 29 July 2014 (UTC)

Yes. The article does not actually state that it is a logical fallacy, even if the article has Tu quoque under the "see also" section. Is "calling the kettle black" in itself an argument fallacy?Star Lord - 星王 (talk) 23:04, 29 July 2014 (UTC)

Tu quoque or the "appeal to hypocrisy" is the standard name for this fallacy. Tevildo (talk) 12:42, 29 July 2014 (UTC)

I thought of Tu quoque, but was worried that it was not a good enough fit. In the argument above, the first party accuses the other party of something that the first party is inadvertently guilty of. In Tu quoque, the first party explicitly accuses the other party of making the same mistake as the first party is being accused of. Star Lord - 星王 (talk) 23:04, 29 July 2014 (UTC)

As for whether it's actually a valid argument, that depends on the situation. In an election with only two serious contenders, if one candidate can show that even though he has a poor record in some regard, if his opponent has a worse record in that respect, then the lesser of two evils argument applies. StuRat (talk) 13:19, 29 July 2014 (UTC)

You are right. Agreed. Mostly wondering of "calling the kettle black" is in itself is a argument fallacy. Star Lord - 星王 (talk) 23:04, 29 July 2014 (UTC)

This is a statement, an observation, an assertion. It is not an argument. (If the speaker means to say that "He is engaging in personal attacks against his opponent", he/she is not expressing his/herself well.) John Champagne (talk) 14:27, 31 July 2014 (UTC)

Renovation project of the United Nations headquarters "Capital Master Plan"

Is it really true, that the "Capital Master Plan" is the biggest renovation project since the early 1950s, the opening of the UN headquarters, or do the media only obliterate facts and in fact there were such renovations already in the 1980s, too, but, just to sound spectacular, mention only the ongoing renovation project? --112.198.90.138 (talk) 10:46, 29 July 2014 (UTC)

You probably won't get much of an answer to that other than what is in the official UN website on the project here. In answer to a related question, the FAQ says "The UN spends approximately $19 million a year on maintenance, plus almost $6 million on maintenance staff. However, the building systems have been running approximately 30 years longer than their expected life-cycle." You are welcome to trawl through the masses of GA documents on the project to see if there is anything in them related to your question. --Viennese Waltz 12:19, 29 July 2014 (UTC)

decoded rechargeable battery

What is a "decoded" rechargeable battery (for a digital camera)? I've seen this description on generic batteries. Bubba73 ^{You talkin' to me?} 18:32, 29 July 2014 (UTC)

Quite a few batteries have a chip on them to monitor the number of charge cycles, etc, and, importantly for this application, to prevent (or, at least, make it more difficult) the use of unauthorized generic batteries. See Smart battery. Using such a generic battery is likely to invalidate the guarantee on your camera, and I'm sure the manufacturers will say there's a safety risk, as well. Tevildo (talk) 19:08, 29 July 2014 (UTC)

One safety risk being that it could impact their sales figures? ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:37, 30 July 2014 (UTC)

Resolved

Thanks - I got burned (not literally) on one of those generic camera batteries once. The specs said that it was better than a genuine one. I could get hundreds of shots with the maker's battery but only about 50 with the generic one. It went into the recycle bin. ... And on a laptop battery. It has twice as many cells, and was supposed to last 4 hours instead of 2, but it would only last about 20 minutes. Bubba73 ^{You talkin' to me?} 02:32, 31 July 2014 (UTC)