If electrons move from the negative side to the positive side in a battery (thus creating electricity when they flow), why does the same circuit with two separate batteries not create electricity?   As you can see in the diagram, electrons should be moving from A to B because the wire is connected from A - side (high pressure) to B + side (low pressure). Why is there no electron flow?
Imagine a battery with the positive terminal connected to ground.  The positive side has a high eletrical potential, ground obviously has a lower electric potential.  Electricity wants to seek a lower potential, and there's no significant resistance between the terminal and the ground.  Shouldn't electricity flow?  I know it doesn't but I don't understand why.  I know you have to close the loop, but why is this necessary?
Abnormal behavior with iwlwifi driver: the device is shown as not working Recently I've installed Kubuntu in a newly bought laptop with an Intel WiFi 6 AX200 network card, I can connect to the wifi without apparent problems but when I open the driver manager in the settings I face this weird situation:  Intel Corporation: Wi-Fi 6 AX200 This device is not working.  [ ] Using iwlwifi driver backport in DKMS format from backport-iwlwifi-dkms (open source)  [ ] Continue using a manually installed driver  [x] Do not use the device   Note that "Continue using a manually installed driver" is the only voice selectable in the list.  Here is some additional information:  $ lspci -nnk | grep 0280 -A3 02:00.0 Network controller [0280]: Intel Corporation Wi-Fi 6 AX200 [8086:2723] (rev 1a)         Subsystem: Intel Corporation Wi-Fi 6 AX200 [8086:0084]         Kernel driver in use: iwlwifi         Kernel modules: iwlwifi  $ rfkill list all 0: hci0: Bluetooth         Soft blocked: yes         Hard blocked: no 1: phy0: Wireless LAN         Soft blocked: no         Hard blocked: no  $ dmesg | grep iwl [    2.888227] iwlwifi 0000:02:00.0: enabling device (0000 -&gt; 0002) [    2.945179] iwlwifi 0000:02:00.0: Direct firmware load for iwlwifi-cc-a0-50.ucode failed with error -2 [    2.945217] iwlwifi 0000:02:00.0: Direct firmware load for iwlwifi-cc-a0-49.ucode failed with error -2 [    2.947244] iwlwifi 0000:02:00.0: TLV_FW_FSEQ_VERSION: FSEQ Version: 43.2.23.17 [    2.947250] iwlwifi 0000:02:00.0: Found debug destination: EXTERNAL_DRAM [    2.947252] iwlwifi 0000:02:00.0: Found debug configuration: 0 [    2.947697] iwlwifi 0000:02:00.0: loaded firmware version 48.4fa0041f.0 op_mode iwlmvm [    3.145585] iwlwifi 0000:02:00.0: Detected Intel(R) Wi-Fi 6 AX200 160MHz, REV=0x340 [    3.159226] iwlwifi 0000:02:00.0: Applying debug destination EXTERNAL_DRAM [    3.160060] iwlwifi 0000:02:00.0: Allocated 0x00400000 bytes for firmware monitor. [    3.336456] iwlwifi 0000:02:00.0: base HW address: 50:eb:71:d7:0b:40 [    3.353553] iwlwifi 0000:02:00.0 wlp2s0: renamed from wlan0 [    4.457920] iwlwifi 0000:02:00.0: Applying debug destination EXTERNAL_DRAM [    4.621843] iwlwifi 0000:02:00.0: FW already configured (0) - re-configuring [    4.629999] iwlwifi 0000:02:00.0: BIOS contains WGDS but no WRDS   Someone have idea why this happened? I run a job every minute to reindex my site's content.   Today, the search engine died, and when I logged in there were hundreds of orphan processes that had been started by cron.  Is there another way using some kind of existing software that will let me execute a job every minute, but that won't launch another instance if that job doesn't return (i.e. because the search engine process has failed)? Storage order vs Result order This is a spin-off question from .   says this on the subject of storage order (clustered index) and the output order     A lot of people believe that a clustered index guarantees a sort order on output. But that's not what it does; it guarantees a storage order on disk.   See, for example, .   I've read the blog post by Hugo Kornelis and understands that an index doesn't guarantee that the sql server reads the records in a specific order. Yet I have a hard time accepting that I can't assume this for my scenario?  CREATE TABLE [dbo].[SensorValues](   [DeviceId] [int] NOT NULL,   [SensorId] [int] NOT NULL,   [SensorValue] [int] NOT NULL,   [Date] [int] NOT NULL, CONSTRAINT [PK_SensorValues] PRIMARY KEY CLUSTERED  (   [DeviceId] ASC,   [SensorId] ASC,   [Date] DESC ) WITH (     FILLFACTOR=75,     DATA_COMPRESSION = PAGE,     PAD_INDEX = OFF,     STATISTICS_NORECOMPUTE = OFF,     SORT_IN_TEMPDB = OFF,     IGNORE_DUP_KEY = OFF,     ONLINE = OFF,     ALLOW_ROW_LOCKS = ON,     ALLOW_PAGE_LOCKS = ON)   ON [MyPartitioningScheme]([Date])   My original query was this:  SELECT TOP 1 SensorValue   FROM SensorValues   WHERE SensorId = 53     AND DeviceId = 3819     AND Date &lt; 1339225010   ORDER BY Date DESC   But I suggest that I could as well use this one (read below for my explanation):  SELECT TOP 1 SensorValue   FROM SensorValues   WHERE SensorId = 53     AND DeviceId = 3819     AND Date &lt; 1339225010   As you can see, my table rows are small (16bytes) and I've got only one index, a clustered. In my scenario, the table consists of 100.000.000 records at this moment (and this will most likely increase tenfold).  When the database server queries this table it has two ways of finding my rows, either it seeks the primary key and thereby reading and returning my values in desc. order of Date, or it has to do a full table scan. My conclusion is that a full table scan on all those records will be way too slow and the database server will therefore always seek the table via its primary key and thereby returning the values sorted by Date DESC Is there a setup where I can leave the water on all summer? Setup restarts the laptop and then restarts the installation all over and over again? Solution  Full solution for producing PDF/X compliant document can be found in MWE and answer to this question:   Adapted MWE and compilation method are taken from Leonid's answer to this question.  Please note that solution requires compilation with TeXLive 2015 (or later).  Original question  I am trying to compile my source with XeLaTeX to produce PDF/X-1a:2001 compliant document. Getting PDF/X-1a:2001 is possible with pdfx package (while using up-to-date TeX distribution), but only when document is compiled with pdflatex.  Since I am using OTF and TTF fonts in my document, I have to use XeLaTeX to compile it. This is MWE:  \documentclass{book} \usepackage[x-1a1]{pdfx} \begin{document} Some text \end{document}   When I try to compile this document with MiKTeX's 2.9 xelatex I get following error and compilation halts:  ! Undefined control sequence. l.111 \pdfminorversion                       =4 %  assumed for PDF/A ;  options may change this for...  ?    Is there any way to compile PDF/X-1a:2001 with XeLaTeX, either using pdfx or different package?  Ps. I used MiKTeX 2.9, because I don't want to update my TeX Live 2013/Debian distribution I normally use. With MiKTeX I get most recent version of pdfx package.  EDIT: Since it isn't obvious from Leonid's answer and is mentioned only in comments, please note that you need TeXLive 2015 in order for Leonid's answer to work fully. TeXLive 2013 (installed by your system's package manager) or MiKTeX 2.9 won't do the trick (this is true as of March 2016; it might change by the time you read this).    I also tried to compile this MWE with LuaLaTeX to see if this works. It didn't. I get following error:  ! Undefined control sequence. \pdfx@findUUID ... \pdfx@tmpstring {\pdfmdfivesum                                                    {#1}} \expandafter \pdfx@e... l.360 \pdfx@findUUID{\jobname.pdf}  ?   In the event version of LuaLaTeX matters: lualatex --version outputs  This is LuaTeX, Version beta-0.76.0-2013062821  (MiKTeX 2.9 64-bit) (rev 4627) Bold row in table aligned with dcolumn I was doing some practice problems that my professor had sent us and I have not been able to figure out one of them. The given equation is:  $-y^2dx +x^2dy = 0$  He then asks us to verify that:  $ u(x, y) = \frac{1}{(x-y)^2}$  is an integrating factor.   I multiplied through to get:  $\frac{-y^2}{(x-y)^2}dx + \frac{x^2}{(x-y)^2}dy = 0$   However, the partial derivatives of these do not equal each other so I am a bit confused... When trying to install CrossOver deb I get "Error: Dependency is not satisfiable libpng12-0" Where did the practice of using apostrophes for possessive nouns but not pronouns originate? Where did the practice of using apostrophes for possessive nouns but not pronouns originate?  For example, possessive nouns (both proper and common) are written with a apostrophe before the final s:        Bill’s, not Bills   Sarah’s, not Sarahs   the bear’s, not the bears   the lizard’s, not the lizards      On the other hand, several possessive pronouns do not have apostrophes before the s:        his, not hi’s   hers, not her’s   its, not it’s   theirs, not their’s   ours, not our’s   yours, not your’s      When and where did this usage originate? Was there any technical advantage of this usage? How to avoid having my father's down payment assistance get taxed as a gift How I would go about getting the current users username or first and last name?  I have been looking at this for the last couple of hours - I was just wondering how I would go about getting their name and then displaying it on the page.  For example the current user is 'John Smith' and in the lightning component I want to output John Smith's name like:     Welcome to our community John Smith! Is the sign of principal components meaningless? Handling Calls to Remove a Moderator This discussion informed our process for seven years, but eventually required updates and augmentation. For discussion regarding the successors to this process, please see:    Stack Exchange has some of the best Moderators around — seriously — and that is due in no small part to the communities who scrutinize and vote in our Moderator elections.  We have a rather formal process for electing moderators, but up until now  has been quite informal. On those rare, rare occasion when things just aren't working out, you can see why it becomes such a sticky business to remove someone from a democratically elected position. Our current process is one of &quot;we've got your back.&quot; The Community Team routinely monitors moderator activities, so if a moderator violates the  or fails to uphold the , we can and do intervene. If the disputes and problems persist without resolution, eventually we can ask someone to step down. That's not good enough. We need a much more transparent and prescribed process for when — and more importantly how — to intervene when on-going problems are going unresolved. In urgent situations, we'll step in to protect a site, but ideally the process should be impartial and not subject to accusations of Stack Exchange simply applying undue influence over a community when the whim strikes. The Question: Before we start bouncing around ideas internally, I'd like to hear what you think. What process should be in place to add some checks and balances to deal with higher issues like possible impeachment of a moderator? When and how would such a process come into play? How should such situations be resolved? How do we keep it from being abused? Have at it. This is a round table vetting of ideas. 2D graphics - why use spritesheets? I have seen many examples of how to render sprites from a spritesheet but I havent grasped why it is the most common way of dealing with sprites in 2d games.  I have started out with 2d sprite rendering in the few demo applications I've made by dealing with each animation frame for any given sprite type as its own texture - and this collection of textures is stored in a dictionary. This seems to work for me, and suits my workflow pretty well, as I tend to make my animations as gif/mng files and then extract the frames to individual pngs.  Is there a noticeable performance advantage to rendering from a single sheet rather than from individual textures? With modern hardware that is capable of drawing millions of polygons to the screen a hundred times a second, does it even matter for my 2d games which just deal with a few dozen 50x100px rectangles?  The implementation details of loading a texture into graphics memory and displaying it in XNA seems pretty abstracted. All I know is that textures are bound to the graphics device when they are loaded, then during the game loop, the textures get rendered in batches. So it's not clear to me whether my choice affects performance.  I suspect that there are some very good reasons most 2d game developers seem to be using them, I just don't understand why. Google Chrome on a fresh CentOS 7.1 not starting up Pluralizing Numbered Items On the Stack Overflow help center article about review queues, , it says on the bottom:  Note: These two queues do not exist on Meta sites.  But there are Late Answer and First Posts review queues on Meta Stack Overflow, as far as the  says. So shouldn't that last sentence be removed? I've searched the net for such information and found different command lines, like these ones:  sudo apt-get remove application sudo apt-get remove application*  sudo apt-get remove --purge application sudo apt-get remove --purge application*  sudo apt-get purge application sudo apt-get purge application*   So, what is the correct way? Is it necessary to use that "*"?  After that, I also found these commands:  sudo updatedb sudo locate application sudo rm -rf (file/folder name) Rerouting stdin and stdout from C