If I have a power supply that says +5.0V/3.0A, does that mean that it can go up to 3 amps or does that mean it always has 3 amps in the circuit all the time?  If I need something that takes 500mA, and I connect it to a breadboard, proto board, or PCB, will it only pull the 500mA?
Power supplies are available in a wide range of voltage and current ratings.  If I have a device that has specific voltage and current ratings, how do those relate to the power ratings I need to specify?  What if I don't know the device's specs, but am replacing a previous power supply with particular ratings?  Is it OK to go lower voltage, or should it always be higher?  What about current?  I don't want a 10 A supply to damage my 1 A device.
Is it normal for a fast prime to exhibit purple fringing in middle of the image? I have just bought a Nikon 50mm f/1.8D prime lens.  I took this picture (leg of my glasses frame on a mouse, and a LED desk lamp is on top of it) : f1.8, 1/80s, ISO 200   The purple fringing is right in the middle of the picture. Does it happen very often to this lens? In the PGF/TikZ manual, sometimes I see the option right of=somenode instead of right=of somenode. They look very similar, but the effects are different.  The distance between nodes positioned with the latter option is boundary-to-boundary, as stated in the manual. However, with the first option, it seems that the distance is shorter. I couldn't find any explanation of the first option in the manual.  My question is: what is the difference between the two options? Is there any explanation in the manual that I missed? $\lim_{x\to0^{+}} x \ln x$ without l'Hopital's rule I have a midterm coming up and on the past exams the hard question(s) usually involve some form of $\lim_{x\to0^{+}} x \ln x$. However, we're not allowed to use l'Hopital's rule, on this year's exam anyways.  So how can I evaluate said limit without l'Hopital's rule? I got somewhere with another approach, don't know if it's useful:   $\lim_{x\to0^{+}} x \ln x = \lim_{x\to0^{+}} x^2 \ln (x^2) = L$ $= (\lim_{x\to0^{+}} 2x)(\lim_{x\to0^{+}} x \ln x)$ $= 0 * L$   Then I just need to prove that L is finite/exists (which means it must be 0) How can I make environment variables "exported" in a shell script stick around? Alternatives to one-way ANOVA for heteroskedastic data I have data from 3 groups of algae biomass ($A$, $B$, $C$) which contain unequal sample sizes ($n_A=15$, $n_B=13$, $n_C=12$) and I would like compare if these groups are from the same population.  One-way ANOVA would definitely be the way to go, however upon conducting normality tests on my data, heteroskedascity seems to the main issue. My raw data, without any transformation, produced a  ratio of variances ($F_{\max} = 19.1$) which is very much higher than the critical value ($F_{\rm crit} = 4.16$) and therefore I cannot perform one-way ANOVA.   I also tried transformation to normalise my data. Even after trials of various transformations (log, square root, square), the lowest $F_{\max}$ produced after transformation with a $\log_{10}$ transformation was $7.16$, which was still higher compared to $F_{\rm crit}$.  Can anyone here advise me on where to go from here? I can't think of other methods of transformation to normalise by data. Are there any alternatives to a one-way ANOVA?  P.S.: my raw data are below:   A: 0.178 0.195 0.225 0.294 0.315 0.341 0.36  0.363 0.371 0.398 0.407 0.409 0.432     0.494 0.719 B: 0.11  0.111 0.204 0.416 0.417 0.441 0.492 0.965 1.113 1.19  1.233 1.505 1.897 C: 0.106 0.114 0.143 0.435 0.448 0.51  0.576 0.588 0.608 0.64  0.658 0.788 0.958 Iteration over std::vector: unsigned vs signed index variable What is the correct way of iterating over a vector in C++?  Consider these two code fragments, this one works fine:  for (unsigned i=0; i &lt; polygon.size(); i++) {     sum += polygon[i]; }   and this one:  for (int i=0; i &lt; polygon.size(); i++) {     sum += polygon[i]; }   which generates warning: comparison between signed and unsigned integer expressions.  I'm new in the world of C++, so the unsigned variable looks a bit frightening to me and I know unsigned variables can be dangerous if not used correctly, so - is this correct? What effect does the Barr body have, in relation to female Turner syndrome? Why do persons with  have  developmental abnormalities, when normal XX-females do not, even though they only have 1 active X chromosome? From what I know, one X-chromosome is inactivated into a Barr body in normal XX-females, but these obviously don't show the symptoms of Turner syndrome. What function does the inactive chromosome have? Quotes insert problem while working with webservice quotes are not inserting may i know what i have to do. my code is     for(integer l=0;l&lt;reqquotes;l++){          qu = new Quote();          qu.Name = qName;          //opp.CloseDate =system.today();           qList.add(qu);             insert oppList;          insert qList;     } I am working on an iGoogle-like application. Content from other applications (on other domains) is shown using iframes.   How do I resize the iframes to fit the height of the iframes' content?  I've tried to decipher the javascript Google uses but it's obfuscated, and searching the web has been fruitless so far.  Update: Please note that content is loaded from other domains, so the  applies. gnome-desktop-item-edit: command not found on Ubuntu 19.10 and later even with the 'gnome-panel' package installed Can you allocate an array with something equivalent to make_shared? Conditional expectation of $\mathbb{E}(X - Y | (X, Y)\in\mathcal{A})$ Given two independent random variables $X \sim \mathcal{U}[-1,5]$ and $Y \sim \mathcal{U}[-5,5]$, what is $$\mathbb{E}\{Y - X | X \le 1, Y &gt; X, Y \in [-1,1] \}\,?$$  I managed to compute the respective probability   $$ \mathbb{P}\{ X \le 1, Y &gt; X, Y \in [-1,1] \} = \mathbb{P}(X \le 1) \mathbb{P}(Y &gt; X) \mathbb{P}(Y \in [-1,1]) = 1/3 * 1/2 * 1/5 = 1/30$$  How do I continue from there? Allow [tag:tag-name] syntax to link to any site The tag  and meta-tag  syntax generate much nicer looking results than merely surrounding your tag with [square brackets].    However, they only work when you're talking about the site you're on.  On Area51, in Chat, and on Meta sites, this is frequently not the case, leading to attempts at syntax like [[tag:failure]](https://superuser.com/questions/tagged/failure), which produces:    Hmm, must be some subtle syntax thing:   : [tag:failure](https://superuser.com/questions/tagged/failure) []: [[tag:failure](https://superuser.com/questions/tagged/failure)] : [tag:[failure]((https://superuser.com/questions/tagged/failure))] : &lt;a href="https://superuser.com/questions/tagged/failure"&gt;[tag:failure]&lt;/a&gt; : [tag:failure][1] \n\n [1]: https://superuser.com/questions/tagged/failure : [more text is a [tag:failure] too](https://superuser.com/questions/tagged/failure)   I give up!  How can I create a link to a tag on another site with tag markdown? How to avoid the pop up message while downloading an application (.exe) using selenium I am trying to download an application and check if it's downloaded into my local system or not. But when I click the download link I have a popup with Save or Cancel options, which is stopping me from downloading the file. I googled and found some solutions and tried to change the profile of Firefox by adding the below code, but it is not working.  firefoxProfile.setPreference("browser.download.folderList", 2); firefoxProfile.setPreference("browser.download.alertOnEXEOpen", false); firefoxProfile.setPreference("browser.helperApps.neverAsksaveToDisk", "application/x-msexcel,application/excel,application/x-excel,application/excel,application/x-excel,application/excel,application/vnd.ms-excel,application/x-excel,application/x-msexcel"); firefoxProfile.setPreference("browser.download.manager.showWhenStarting", false); firefoxProfile.setPreference("browser.download.manager.focusWhenStarting", false); firefoxProfile.setPreference("browser.helperApps.alwaysAsk.force", false); firefoxProfile.setPreference("browser.download.manager.alertOnEXEOpen", false); firefoxProfile.setPreference("browser.download.manager.closeWhenDone", false); firefoxProfile.setPreference("browser.download.manager.showAlertOnComplete", false); firefoxProfile.setPreference("browser.download.manager.useWindow", false); firefoxProfile.setPreference("browser.download.manager.showWhenStarting", false); firefoxProfile.setPreference("services.sync.prefs.sync.browser.download.manager.showWhenStarting", false);   This is the code I added for setting up Firefox preferences, but I still get the popup. I got pretty confused at that question... Can anyone help me understand this question better and/or drop some hints please? Thank you! CPU on Ubuntu running high In the terminal I used "top" to check the processes and how much of the CPU was being used as I thought max was 100%, so I restored 292,000 photos with recoverjpeg on my sda1 HDD, I opened the folder and the Nautalis is  fluctuating between 130% and 170% , should I close the program and am I at risk of my gpu locking up ? I have knowledge about 'Kile' more or less. Now  I am using 'Texmaker'. But  there is a problem in it. In Kile when we write \begin{env} it automatically write \end{env} from the following :  Settings => Configure Kile => LaTeX => Environments => making tick mark on "Automatically complete \begin{env} with \end{env}" we can set it. But in 'Texmaker' automatic environment is not working. How can I do so. I'm looking for a shapefile containing an 1000m or 2000m UTM grid ("graticule"). All I was about to find on the web is a 10000m UTM grid (here: ) and I am aware that a 1000m UTM grid for the whole world might be quite big.  That's why I'm now wondering if and how it would be possible to generate such a shapefile for a part of the world. I would prefer to use open source tools like gdal. Others output formats than a shapefile might be ok too.   Has anyone an idea? Aromatic rings resized with chemfig When I want to reduce the size of a molecule drawn with  I usually put a [scale=0.xx] before the argument of the command. However when I deal with aromatic rings this method doesn't work well, in fact only the carbon skeleton is resized: the 'aromaticity' is not and it's also out of center.  For example:  \chemfig[][scale=0.75]{**6(-------)}\quad   gives me:     How do I achieve a complete resize? Can anyone explain why a semi-simple finite dimensional Lie algebra $\mathfrak{g}$ has to be perfect ?   The natural way to prove something like that would be to look to the algebra generated by the Lie brackets, which when $\mathfrak{g}$ is not perfect would be expected to be solvable. But it doesn't seem to work.