This kind of a configuration struck me when I read  question.   The original question asked how the force on the two charges would change if a metal plate was inserted between them. This question addresses what would happen if it was an infinite plane (those are so much more convenient).  I gave it some thought and the result is rather interesting.   EDIT: This question is very different from the original in that:   The infinite plane is grounded, a plate with definite dimensions does not have to be One can't use image charges with the plate If the plate is uncharged, positive charges will accumulate on the edges and create their own field, in case of an infinite plane these positive charges are at infinity and do not affect the configuration. A plate does not provide electrostatic shielding or a simple boundary region to apply the uniqueness theorem in. The charge distribution on a finite plate is much harder to model.
If a thin metal plate is placed between two charges $+q$ and $+q$, will this cause a change in the electrostatic force acting on one charge due to another? What is the concept behind this? What will happen if the metal plate is thick?
Say my opponent plays a planeswalker during their first main phase.  I have a  or some other effect that will kill it after it is already in play, but before they use any of its abilities.  I could respond to them using a +1 ability, but I want to kill it before that effect goes on the stack.  In most casual situations, it would basically come down to whether I say "Hero's Downfall" first, or they say "+1" first.  But I can't imagine that's how it's supposed to work.  Is there a time between when the planeswalker hits the battlefield and when they activate its abilities that they must let me respond? It seems to me that situations like this arise frequently, and they are resolved simply by who speaks up first, which is horrible for such a rules-oriented game. Paging using ldapsearch I am searching an LDAP directory that has a much larger number of results than the sizelimit currently set,500, by slapd.conf that for all intents and purposes cannot be changed)  My idea was to keep running ldapsearch but from a different offset each time (501, 1001, etc.) until all results have been obtained.  I have seen the , and it appears that this is handled for you using the -E options:  -E [!]&lt;ext&gt;[=&lt;extparam&gt;] search extensions (! indicates criticality)          [!]domainScope              (domain scope)          [!]mv=&lt;filter&gt;              (matched values filter)          [!]pr=&lt;size&gt;[/prompt|noprompt]   (paged results/prompt)          [!]subentries[=true|false]  (subentries)          [!]sync=ro[/&lt;cookie&gt;]            (LDAP Sync refreshOnly)                  rp[/&lt;cookie&gt;][/&lt;slimit&gt;] (LDAP Sync refreshAndPersist)   So i tried: ldapsearch -h $HOST -p $PORT -x -L -b "$BASE" '*' '+' -E pr=$SIZE  However when the results (even paged results with size = 50 for example) hit 500, I get the same error as if the results were not paged:  Size limit exceeded (4)  I have seen in the man pages there is another option for virtuallistview but have been unable to find examples for it, and as well I dont think my version of ldapsearch has this option.  The goal here is to create a backup using ldapsearch and the -L option to create an ldif file that is suitable for restoring the database.  A few google searches show up with the same problem I'm having, but none have an applicable solution.. I'm sure this is a newbie question, but I can't figure this out. I have tried to follow the advice here:  and here:   But I can not seem to be able to generate any font change. I either get no change or error messages.  Here is the output of one failed attempt to change the font to Times using this command:  \rmfamily \renewcommand{\rmdefault}{ptm}     Apparently I either don't have a correct package installed or...  The output says " Metric (TFM) file not found." but I am not sure where to go from there. There is no set of all sets.. So there are a few posts about this already, but they skip over the problem I have.  The proof of Cantor's theorem elegantly shows that if we consider $f:A\rightarrow \mathcal{P}(A)$, the set $B=\{x\in A : x\not\in f(x) \}$ by its definition cannot lie in the image of $f$, precluding it from being a bijection - hence power sets have strictly greater cardinality.  But now, I thought one (obvious) way to characterise the "set of all sets" would be $S=\mathcal{P}(S)$, as indeed, it contains all possible sets (perhaps here is the problem, but I don't immediately see how using this as a definition for the set of all sets is bad). Now consider simply taking the identity function $i:S\rightarrow S$. Then $B=\{x\in S : x\not\in x \}$ - the set of all sets which do not contain themselves. But this doesn't exist. It's exactly the set of Russell's paradox. If this isn't a set, and so is not in $S$, then the proof no longer offers an obstruction to $i$ being surjective.    Each other post I've seen on the matter uses Cantor's theorem to show such a set doesn't exist. My query is to find that something else that must be happening, since I think the proof has issues for this particular set. I'm expecting other issues to arise with the definition $S=\mathcal{P}(S)$... Fixing a code to highlight formulas and text on several lines In  I've found the following amazing code to highlight text on several lines.  The problem is that code dosen't work well with formulas : for example, fraction using the mode display are partially out of the highlighting frame.   Here is the code with one content showing the problem.  \documentclass{article}     \usepackage{soul}     \usepackage{tikz}     \usetikzlibrary{calc}     \usepackage{amsmath}     \usepackage{xcolor}      \makeatletter         \newcommand{\defhighlighter}[3][]{%             \tikzset{every highlighter/.style={color=#2, fill opacity=#3, #1}}%         }          \defhighlighter{yellow}{.5}          \newcommand{\highlight@DoHighlight}{             \fill[                 outer sep = -15pt, inner sep = 0pt,                  every highlighter, this highlighter              ](                 $(begin highlight)+(0,8pt)$) rectangle ($(end highlight)+(0,-3pt)$             );         }          \newcommand{\highlight@BeginHighlight}{             \coordinate (begin highlight) at (0,0) ;         }          \newcommand{\highlight@EndHighlight}{             \coordinate (end highlight) at (0,0) ;         }          \newdimen\highlight@previous         \newdimen\highlight@current          \DeclareRobustCommand*\highlight[1][]{%             \tikzset{this highlighter/.style={#1}}%             \SOUL@setup             %             \def\SOUL@preamble{%                 \begin{tikzpicture}[overlay, remember picture]                     \highlight@BeginHighlight                     \highlight@EndHighlight                 \end{tikzpicture}%             }%             %             \def\SOUL@postamble{%                 \begin{tikzpicture}[overlay, remember picture]                     \highlight@EndHighlight                     \highlight@DoHighlight                 \end{tikzpicture}%             }%             %             \def\SOUL@everyhyphen{%                 \discretionary{%                     \SOUL@setkern\SOUL@hyphkern                     \SOUL@sethyphenchar                     \tikz[overlay, remember picture] \highlight@EndHighlight ;%                 }{}{%                     \SOUL@setkern\SOUL@charkern                 }%             }%             %             \def\SOUL@everyexhyphen##1{%                 \SOUL@setkern\SOUL@hyphkern                 \hbox{##1}%                 \discretionary{%                     \tikz[overlay, remember picture] \highlight@EndHighlight ;%                 }{}{%                     \SOUL@setkern\SOUL@charkern                 }%             }%             %             \def\SOUL@everysyllable{%                 \begin{tikzpicture}[overlay, remember picture]                     \path let \p0 = (begin highlight), \p1 = (0,0) in \pgfextra                     \global\highlight@previous=\y0                     \global\highlight@current =\y1                     \endpgfextra (0,0) ;                     \ifdim\highlight@current &lt; \highlight@previous                         \highlight@DoHighlight                         \highlight@BeginHighlight                     \fi                 \end{tikzpicture}%                 \the\SOUL@syllable                 \tikz[overlay, remember picture] \highlight@EndHighlight ;%             }%             \SOUL@         }     \makeatother   \begin{document}  Lorem ipsum \highlight{dolor sit amet, consectetur adipis-icing elit, sed do eiusmod tempor} incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation \highlight[red]{ullamco $laboris$ nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit} in voluptate velit esse cillum dolore eu fugiat nulla pariatur.  Excepteur sint occaecat \highlight[green, draw=blue]{cupidatat non proident  $\dfrac{789}{7889}$ % The frame is not good for that formula ! suntinculpaquiofficiadeseruntmollitanimidestlaborum. Loremipsumdolorsitametconsecteturadipisicingelitseddoeiusmodtemporincididuntutlabore-etdoloremagnaaliqua.} I suppose I could write some more text here.  \end{document}     Is someone could help me to fix it? Which is better to do client side or server side validation?  In our situation we are using    jQuery and MVC.   JSON data to pass between our View and Controller.     A lot of the validation I do is validating data as users enter it. For example I use the the keypress event to prevent letters in a text box, set a max number of characters and that a number is with in a range.   I guess the better question would be, Are there any benefits to doing server side validation over client side?    Awesome answers everyone. The website that we have is password protected and for a small user base(&lt;50). If they are not running JavaScript we will send ninjas. But if we were designing a site for everyone one I'd agree to do validation on both sides. How do you reopen a closed question? This might be a completely wrong question, but this is bothering me since many days ago. Given the mass (Sun) curves the space around it, gravitation is the result of such curved space (Correct me if I am wrong, source: A Documentary film). Given any point on a circle with center same as center of the mass, curvature in the space should be equal (Intuition).   Planets rotate around the Sun because of the curve in the space they should follow a circular path and the distance between planet and Sun should be at a distance.  Given the fact that earth has a elliptical orbit around the sun, and the distance between Earth and Sun varies according to position of the earth. Why do we have a elliptical orbit not a circular orbit. Is it possible to reset all folder permissions? I was wondering if it was possible to reset all the folders' rights. I was having trouble when trying to install LAMP on my Ubuntu 11.04 installation, and I modified many permissions like /var /etc and I want to cancel everything I did and have permissions set to how they would be after a new install. Has anyone ever booked a flight with ?  I am just wondering where they get their prices and data from, and if I might find a cheaper flight by using something like Expedia or Travelocity. Point vs Pixel: What is the difference? What is the difference between points and pixels? I have a laptop that has Windows 8 which I use for playing Minecraft. However when using the inventory, I have to hold my mouse to drag and pick the items and I don't like that.   I have tried switching mouses but that didn't work, is this possible to fix? Database files that are built using SQL 2008 are not compatable with 2005. Is there a work around? How to prepare files for rsync on a case insensitive filesystem? I am transferring a large number of files on a HFS+ filesystem.  The files are currently on ext2 partitions.  I have conflicts due to case insensitivity of the target partition (HFS+).  I want to identify the files that have duplicates filenames once they are in lower case, and delete them if they are actually duplicates.  I also found that I will have duplicate folder names if I convert everyhing to lower case. Basically these hard drives contain years of unsorted data, and I happen to have this problem with folder names too.   Does this seem reasonable:  find . -type f | while read f; do echo $f:l; done | sort | uniq -d    $f:l is ZSH for convert to lower case.  Now I want to keep only one instance of each file that have duplicates. How to do this efficiently ?  I do not want to find files with duplicate content, unless they have the same lower case filename. I will deal with duplicates later. How do you prevent web pages from appearing in the Google search index? I have some web pages that Google has indexed. I have now added a robots.txt file to exclude them, but should I also add a noindex tag? If so, then how do I do so? Which graphics formats can be included in documents processed by latex or pdflatex? I am making the check for update script for my theme  I have 2 text files. First one is called "current.txt" and contains the current version. There is 4.1.1 string in that text file.  Second one is called "latest.txt" and contains the latest version. There is 4.2 string in this text file.  So here is the code  echo "Checking update"; x=$(cat ./current.txt) y=$(cat ./latest.txt) if [ "$x" -eq "$y" ] then        echo There is version $y update else        echo Version $x is the latest version fi   What it mean is if current.txt is NOT the same with latest.txt then it will say "there is version 4.2 update". If not, it will say "version 4.1.1 is the latest version"  But when I try to run it. I get this error  Checking update ./test.sh: line 4: [: 4.1.1: integer expression expected Version 4.1.1 is the latest version   So what am I doing wrong with this? May I get off in an intermediate city of my route during transfer? I want to go from Panamá to Turkey. There're direct flights of Turkish Airlines that are expensive. And there're flights Panamá -&gt; Istambul -&gt; Baku there're cheaper 2 times of the same airline. The transfer in Istambul takes 6 hours.    Will it be a violation if I buy a ticket Panamá -&gt; Istambul -&gt; Baku and leave in Istambul? How to count the number of set bits in a 32-bit integer? The exercise is: Prove that $-(-v)=v$ for every $v \in V$  Proof Suppose  $v \in V$ and $V$ is a vector space. Then $-(-v) \in V$ as result of the scalar multiplication property and $-(-v)=-(-1\cdot v)=-1 \cdot(-1\cdot v) =(-1 \cdot-1)\cdot v = 1 \cdot v = v $ The desired result $-(-v)=v$ holds.  The solution manual gives the proof:  Proof   I just wanted to make sure that the way I did the proof isn't missing anything?Thanks