Direction of emf and it's physical sense? I have a situation where  there exist a time varying magnetic field and a circular loop place perpendicular to it. Let us assume that the magnetic field is $\vec B=\frac{B_0 t}{\tau}$ . I tried to modify this problem is my own way that I will be discussing later right now is irrelevant. Also please note, the minor details of this problem need not be considered like polarization etc, or anything, think of it as high school level stuff.  So, my question is that, I know that by using Faraday law $e=-\frac{d\phi}{dt}$   I will get the result as $e=-\pi r^2 \frac{dB}{dt}$(not substituting value yet as it's not required).  So, now i have got this emf whose meaning i don't understand, what I mean to say is what would this emf look like , what would be it's direction, end point , start point, etc. Basically I can't understand it's physical sense and direction(loosely speaking here , please note that this direction, i meant to be associated with the path integral).  Also, suppose that I replace the situation with an circuit having equivalent emf what would it look like?  Now continuing with the problem by the $e=-\vec E.\vec dl$ , I was told that there exist a induced electric field having circular loop and direction I don't remember but with upward magnetic field seems to be anti-clockwise(please verify and explain!)  Gives $E=\frac{1}{2}r\frac{dB}{dt}$ so, the only problem is how I can visualize this emf and electric field. As well is there any way to produce current using that emf? Connecting somewhere? Or an equivalent circuit?  EDIT: The equation of electric field of course implies that $E$ is constant for a given $r$ , so this implies the circular nature of  electric field but what about it's direction, suppose that if i connect a wire loop in that electric field would a current flow through it, would that be the direction of emf? (Suppose that material is not affected by magnetic field).
Post Problem Analysis - Rod in a cylindrical time varying magnetic field? A metal rod of length $l$ is placed (as shown in figure) in a cylindrical time varying magnetic field. Find the potential difference across it.   My answer:  As electric fields as forming circles around the centre with magnitude $$\frac12r\frac{dB}{dt}$$ whose magnitude is same along any chord at a fix distance from centre: $$\Delta V=E.l=\frac12r\frac32at^{\frac12}.l$$ $$\Delta V=\frac34arlt^{\frac12}$$  My question: Is $\Delta V =V_M-V_N$ or $\Delta V=V_N-V_M$ $\bf OR$ equivalently which side is at high potential?  Possible    $(i)$ As Field lines are circular from $M$ to $N$, $M$ must be high potential. $(ii)$ As this field line apply a force on electrons- in the rod- towards left, then $M$ must have excess $e^-$ and $N$ must have deficiency; so $N$ would be high potential as $M$ is $(+)$ and $N$ is $(-)$.
I washed and dried my passport by mistake, do I need a new one? Around two years ago I washed and dried my passport by mistake at the laundry room. My ID, my old US student visa and my stamps from european countries are still readable but the pages are not "flat" anymore and the front cover is kind of erasing (some parts of the Brazil symbol is gone).   In April I'll travel to US for a conference, I'll need to get a new US visa (B1/tourism visa) but I'm worried if my passport is not "good to go" anymore because it was "washed and dried". Apparently there is an electronic chip in it and I don't know if it is still working.  Should I get a new passport or can I save some money and time and use this one? It expires only in 2019. Imaging new hard drive in Windows 7 laptop? I'm upgrading my Windows 7 laptop to a new hard drive.  How can I clone or image the old hard drive over to the new hard drive, so that it looks like nothing has changed (other than the new hard drive) to my operating system and applications?  Can I use what is built into Windows 7 Backup or should I use something else? I learned recently that when an object moves with a velocity comparable to the velocity of light the (relativistic) mass changes. How does this alteration take place? Are bicategories and lax 2-categories the same? html - how to remove right margin completely? Is there a way to make the following return true?  string title = "ASTRINGTOTEST"; title.Contains("string");   There doesn't seem to be an overload that allows me to set the case sensitivity.. Currently I UPPERCASE them both, but that's just silly (by which I am referring to the  issues that come with up- and down casing).  UPDATE This question is ancient and since then I have realized I asked for a simple answer for a really vast and difficult topic if you care to investigate it fully. For most cases, in mono-lingual, English code bases  answer will suffice. I'm suspecting because most people coming here fall in this category this is the most popular answer.  answer however brings up the inherent problem that we can't compare text case insensitive until we know both texts are the same culture and we know  what that culture is. This is maybe a less popular answer, but I think it is more correct and that's why I marked it as such. Android Preferences: How to load the default values when the user hasn't used the preferences-screen? Need a comma before an adverb as last word in sentence? How to properly install Java in OS X Is there a way to test an application where you simulate a hundred different clients connecting to a IIS server and asking the same data? At the customer where our project is running they have 400 computers and they often do stress tests with all computers. I on the other hand have only got my laptop... (and a development server).  (In my case the data is asked through a WebORB Gateway). Derive equation for a cantilever in SHM How does a battery ( primary cell ) work? I'm having an hard time understanding primary cells. There are plenty of videos and explanations about the reactions that happen inside the battery, but you must have a strong background in chemistry to really understand them. Instead, I would love to have a description that abstracts from the chemicals details, and still manages to explain its basic working princeples! I would like it to address the following questions/doubts:     Electrons flow form higher potential to lower potential so, when you buy a  battery, is an electric field already there, before connecting it to a wire? (I presume yes) So,How is this field created? Are the electrons at the top and the protons at  the bottom, or just electrons at the top and the bottom is neutral? How are electrons kept together in the same place before connecting the battery  to the wire? What does prevent them to flow inside the battery? How does the battery pump up the electrons? and at which rate? What makes it burn out? and after many cycles does it burn out?       I know there are a lot of questions but my mind is exploding. I don't expect everything to be abstracted from the chemicals but as long as you can through analogies, or intuitive principles, i'd love that. Anyway the main intent of the answer must be addressing the doubts listed. I am creating a type of adventure map. Once you enter the map, you step on some pressure plates that are supposed to seamlessly close the wall behind you. For some reason this command does not work when in a command block or just in text. Here is the command:  /fill -17 4 -109 -18 5 109 minecraft:light_gray_concrete   The output it gives me is "That position is not loaded". I am on a singleplayer superflat world in 1.14.3. Any help would be very appreciated! Let $a&gt;b&gt;0$ and let $n \in N$ satisfy $n \geq 2$.  Prove that $$a^{1/n}-b^{1/n}&lt;(a-b)^{1/n}.$$  If we let $a=x$ and $b=x-1$, then we need to show that $f(x):=x^{1/n}-(x-1)^{1/n}$ is decreasing for $1\leq x$ (which means that $f'(x)\leq 0$ and $f$ is differentiable), and evaluate $f$ at $1$ and $a/b$. How to recover a deleted file from /data partition? Brand new laptop, two years in storage, will the battery be ok? I have an opportunity to buy a brand new (sealed box) EliteBook 8470p laptop for a good price.  The date of manufacture goes back to around March 2013, which is bang on two years ago.  Given that it's been two years, what state will the supplied Lithium-Ion battery be in? Still usable? Click Answer your own question Check community wiki A dialog box     Are you sure you want to make this post Community Wiki?   will appear, Click OK or Cancel; The same dialog will appear again.   Google Chrome 44.0.2403.107 / Windows8.1 / site rev 2015.7.25.3609 How to list files in a zip without extra information in command line In my bash command line, when I use unzip -l test.zip I get the output like this:  Archive:  test.zip   Length      Date    Time    Name ---------  ---------- -----   ----    810000  05-07-2014 15:09   file1.txt    810000  05-07-2014 15:09   file2.txt    810000  05-07-2014 15:09   file3.txt ---------                     -------   2430000                     3 files   But I am interested only by the lines containing the file details.  I tried to make filtering using grep like this:   unzip -l test.zip | grep -v Length | grep -v "\-\-\-\-" | g -v Archive | grep -v " files"  But it is long and prone to error (e.g a file name Archive in this list will be dropped)  Is there any other options with unzip -l (I checked the unzip man page and did not find any) or another tool to do so?  It is important to me to not really unzip the archive but just to look what files are inside. Do we have negative prime numbers? Do we have negative prime numbers?   $..., -7, -5, -3, -2, ...$ Followup to "".  It is argued that even a tiny residual charge would result in huge amounts of electricity in bulk matter, everything would be different, etc. I do not find that a convincing answer: suppose $n$ protons plus $n+1$ electrons are neutral. Why wouldn't we also expect there to be $n$ protons to every $n+1$ electrons? That is, there is no bulk matter problem if every $n$'th atom is a negative ion (for hydrogen).  Now, what empirical lower bound can we give for $n$ in that kind of scenario?