I'm just starting out learning about Electronics but something has puzzled me . I have read that current flows through a circuit from negative part of a battery to positive  .  but what puzzles me is I made a simple series circuit  of a  Diode - Resistor  - LED  ........... Positive terminal is connected to the Diode  so how does the LED light up if electricity flows from negative to the positive terminal ? If  electricity flows from negative to positive the Diode would stop the flow and the LED would not light up?
Im having a bit of trouble drawing a circuit with a diode in. I know the current flows from negative to positive, but convention says that current goes from positive to negative.  When drawing a circuit with a diode do you draw the arrow pointing to the positive (matching the actual flow of electrons) or towards the negative terminal (matching conventional current)?  If you follow convention then surely when building circuits from the diagram the diode will not allow current as it is actually facing the incorrect way?
What is the best way to close an ASPX page from the code-behind?    I have a button event handler that I want to close the page after the user has clicked an ASP.NET button on the page.  I have tried to programmatically add a JavaScript method that contains a window.close() command to the OnClientClick event to close the page but it does not work.  The button is also a asp:AsyncPostBoskTrigger for an AJAX Update Panel.  The application uses .NET Framework 3.5. How to force the Y axis to only use integers in Matplotlib? Under Windows, most applications and application data are stored in a special directory known as C:\Program Files (and occasionally C:\Program Files (x86)). What is the Ubuntu/Linux equivalent to this path? Is there even one? Two definitions of $\limsup$ Feature request: Add pronouns to usercards? One of the questions people have raised about the new rules about pronouns is how users will know what pronouns are preferred.   We've had a trolling question which got  when the user included their preferred pronouns at the bottom of the question, and I agree that particularly on Stackoverflow (rather than sites like Interpersonal Skills or Workplace), this should be considered as 'noise' since it isn't the strict Q&amp;A this site is about. (The codez should work whatever your gender).  Currently, the suggested way of displaying your pronouns is to put it in your profile's 'About Me' section. However, this is suboptimal, since it requires opening a new page.  I suggest adding a 'preferred pronouns' field in the user profile, and displaying this on a user's usercard. There's currently a 'new contributor' label, so it could be similar to that, with she/her pronouns or whatever they choose.  In comments, it could be appended to the reputation score that currently gets shown when you hover over a name:   4,305 reputation, she/her pronouns  The default would be blank. No flair updates, no hover-in-comments update. If a user fills in this field in their profile, then it will show. What is a tensor? I have a pretty good knowledge of physics, but couldn't deeply understand what a  is and why it is so fundamental. Is there a package to secure rendered pdf with a password? Is there a package and command that can secure rendered pdf with a password? Why are two different concepts both called "heap"? If $A\simeq\prod A_i$ then $\sum e_i=1$ Given $A$ commutative ring with unity. If we have rings $A_1,\dots, A_n$such that $A\simeq A_1\times \dots \times A_n$ there are $e_1,\dots,e_n$ idempotent elements of $A$ such that $e_1+\dots+e_n = 1$ and $e_i e_j =0$ if $i\neq j$.  I'm not sure how general the proof should be written...  The isomorphic relation suggest that if $f$ defines the isomorphism then there is a $(a_1,\dots, a_n)\in \prod A_i$ such that $f(a_1,\dots,a_n)=1\in A$. Could it work thinking of the idemmpotent terms as $e_i=(0,\dots,0, a_i,0, \dots,0)?$ This should satisfy $e_i e_j =0$ if $i\neq j$. But I have two problems with it (1) I don't see why $e_i$ should idempotent as no assumptions in regard to the existence of idempotent elements in $A_i$ has been made. (2) The sum $\sum e_i=1$ has no reason to be true. Generate multiple renders of same scene, each at a different resolution? I would like to generate several renders of a static scene, each render being a different size (eg 1024x1024, 512x512 etc). Other than the size, each render will be identical.  Is there a way of doing this using, say, the command line, or a script? I am currently doing this by manually changing the dimensions within the render panel every time, but I was wondering if there's a quicker way.  I am using Blender Internal in this specific instance.  Many thanks Can open, unsafe nuclear fusion reaction burn the atmosphere? I happened to hear people saying that the nuclear fusion bomb tests could set the atmosphere on fire. I have some serious doubts about that - but I have no facts. Nuclear fusion reaction requires $15*10^{6}$ kelvins to start. If we produce such temperature in "open air" would the atmosphere become a fuel for further fusion? Shouldn't the whole thing just be torn apart by its terrible pressure? Citation colour with Beamer + Hyperref + Natbib I'm using natbib for citation with a custom bibstyle. I'm working on a presentation using LaTeX beamer and for some reason the citation marker doesn't have the colour that is specified to hyperref. The citation marker is black instead of green. I'll give you a MWE:    \documentclass{beamer} \hypersetup{   colorlinks,   citecolor=green,   linkcolor=red }  \usepackage{filecontents} \begin{filecontents}{mybib.bib} @ARTICLE{Bar2011,   author = {F. Foo and F. Bar},   title = {Foo and Bar},   journal = {Journal of Foo},   year = {2011},   volume = {1},   pages = {1--3} } \end{filecontents}  \usepackage[comma,numbers,sort&amp;compress]{natbib} \bibliographystyle{plain}  \begin{document} Dummy referefence to~\cite{Bar2011} \bibliography{mybib} \end{document}   For the purpose of the MWE I have selected the plain bibstyle, however, changing that to something else (including the custom style I want to use) doesn't affect the label colour.    Is there any patch for this problem? SciFi movie (or miniseries) of the afterlife I am trying to find the name of a direct to TV movie, possibly a 2-3 part miniseries which I believe aired on the SciFi channel in the 90s. I don't remember who starred in it, but the movie opened with an astronaut attempting reentry whose shuttle ends up exploding. He awakes in a large bubble of air in a river and after reaching the surface and swimming to shore, meets several other people, from seemingly many different times throughout history (including one alien, who died on Earth).  Over the course of the movie, we learn the world is the afterlife, where everyone goes when they die. The major plot involves launching a steamboat (built by Mark Twain, no less) to travel up a river to the mountains, where the beings responsible for bringing everyone to this world are.  Does anyone know what the title of this movie/miniseries is? How to prevent unification when animating in photoshop? I am trying to create an animated gif where text drops down and smashes into the background and cracks it. Whenever I try and transform it though, the transformation is applied to all frames. How do I prevent this? I'm using Adobe Photoshop CS6 (64-bit) I created the shiftcommandn shortcut for Firefox in Syst Prefs to match other browsers' behavior.     It registers in the Firefox Menubar.     But pressing the shortcut opens a new non-private window, and it loads there the first item in my "Top Sites".   I imagine I could create another shortcut to override this behavior, but what is this behavior? I don't see anything highlighted in the Firefox Menubar when I hit the shortcut. Or might there be another solution (other than using a different shortcut to open new private windows)?   Problem exists on both Mojave and High Sierra. Default Firefox shortcut (shiftcommandp) still opens a new private window. I found this heart while exploring the crimson biome - what is it? How do I set a custom resolution? $$f(x,y) = \left\{\begin{array}{cc} \frac{xy}{x^2+y^2} &amp; (x,y)\neq(0,0) \\ f(x,y) = 0 &amp; (x,y)=(0,0) \end{array}\right.$$  In order to verify if this function is differentiable, I tried to prove it by the theorem that says that if $\frac{∂f}{∂x}$ and $\frac{∂f}{∂y}$ exist and are continuous at the point $(x_0,y_0)$, then the function is differentiable at this point. So I did:  $$\frac{\partial f}{\partial x}(0,0) = \lim_{h\to 0}\frac{f(0+h,0)-f(0,0)}{h} = 0$$ $$\frac{\partial f}{\partial y}(0,0) = \lim_{h\to 0}\frac{f(0,0+h)-f(0,0)}{h} = 0$$  so we have that the partial derivatives at point $(0,0)$ is $0$. Now, if we take the derivative at $(x,y)\neq (0,0)$ and then take the limit of it as $(x,y)\to(0,0)$, we can see if the derivatives are continuous or not. So here it is:  $$\frac{\partial f}{\partial x}(x,y) = \frac{y(y^2-x^2)}{(x^2+y^2)}$$  but   $$\lim_{(x,y)\to(0,0)} \frac{y(y^2-x^2)}{(x^2+y^2)} $$ does not exist (by wolfram alpha... but can anybody tell me an easy way to prove this limit does not exist? easier than taking the limit in different directions?), therefore the derivative is not continuous at $(0,0)$, so we can't say $f$ is differentiable at $(0,0)$, but for $(x,y)\neq (0,0)$ the function is continuous, as it is a quotient of continuous functions. So $f$ is at least differentiable at $(x,y)\neq (0,0)$.   Now, to verify differentiability at $(0,0)$ I think we must use the limit definition of differentiablity: A function is differentiable at $(0,0)$ iff: $$\lim_{(h,k)\to (0,0)} \frac{f(0+h,0+k)-f(0,0)-\frac{\partial f}{\partial x}(0,0)-\frac{\partial f}{\partial y}(0,0)}{\|(h,k)\|} = 0$$  Let's calculate this limit:  $$\lim_{(h,k)\to (0,0)} \frac{f(0+h,0+k)-f(0,0)-\frac{\partial f}{\partial x}(0,0)-\frac{\partial f}{\partial y}(0,0)}{\|(h,k)\|} = \\ \lim_{(h,k)\to (0,0)} \frac{\frac{hk}{h^2+k^2}}{\sqrt{h^2+k^2}} = \\ \lim_{(h,k)\to (0,0)} \frac{hk}{(h^2+k^2)\sqrt{h^2+k^2}}$$  which I think, it's a limit that does not exist, therefore the function isn't differentiable at $(0,0)$ Can I fly back to Italy if my Italian residency card has expired and is being renewed? Hearing a sound backwards because of Doppler effect