As far as I understand it, a steady/stationary/constant current is defined to have $dJ/dt=0$ (i.e., no explicit time dependence). So I would say that sinusoids cannot produce steady currents, yet google tells me that there are such things as sinusoidal steady currents. How is that possible given that such sinusoidal currents have an explicit time dependence ($sin(\omega t$))?   When I imagine a steady current, the easiest picture is of a line current that has one $J=$constant (no time dependence), which produces a constant magnetic field loop at some radius away from the line/wire. How can a time-varying sinusoid also produce a constant magnetic field? Are 'steady sinusoidal currents' instead referring to a spatially-varying sinusoid (like a constant current density, but going around in a circular loop, i.e., a magnetic dipole)?
I am in the process of completing some homework and have come across a question that says: "What is the steady-state current?" It is asking in reference to a circuit that includes two capacitors in parrallel and a DC source of 24V and an AC source given by $\epsilon = 20 \cos(120 \pi t)\ \text{V}$, where $t$ is in seconds. I assume that it is asking when the current is constant. Because naturally the current is not constant due to the AC source, would I just consider the DC source for this?
Inner join vs Where Is there a difference in performance (in oracle) between  Select * from Table1 T1  Inner Join Table2 T2 On T1.ID = T2.ID   And  Select * from Table1 T1, Table2 T2  Where T1.ID = T2.ID   ? Evaluating $\int_{0}^{1}\int_{0}^{1}\sqrt{x^{2}+y^{2}}dxdy$ using polar coordinates. I want to evaluate the integral $\int_{0}^{1}\int_{0}^{1}\sqrt{x^{2}+y^{2}}dxdy$ using the substitution $x=r\cos\theta$ and $y=r\sin\theta$ where the Jacobian is given as $|J(r, \theta)|=r$ and thus $dxdy=rdrd\theta$.  I need to set the range for $r$ and $\theta$. For $\theta$, it seems obvious that it ranges from $0$ to $\frac{\pi}{2}$ to cover all parts of the rectangle. But I am confused with the range for $r$. Would it be OK to set minimum $r$ as $0$ and maximum $r$ as $\sqrt{2}$, which is the diagonal of the square domain? I think I am confused with the fundamentals of integration. The strange thing is that opened scripts or newly opened ones are working fine. It's the new created C# scripts that are not working.  With not working, I mean the MonoBehaviour is not in light blue color it's in black color. In this screenshot I took, I marked it with a red circle.    What have I tried so far? I have closed Visual Studio and started over again.  Since it didn't solve it, I closed the unity editor and started it over again, to no avail.  I pressed 'clean solution', I pressed 'rebuild solution', I pressed 'build solution'.  What else can I do ? And why are the other scripts working fine? If I type gameo...it will auto complete it to GameObject but in this specific script it's just not working.  This is a screenshot of the editor. I have in the Hierarchy a Ladder object.  In the Assets I created a folder name Ladder and a script name Ladder. But this Ladder script is not working.    This is the Ladder script and this script was working before but once I created another script inside the ladder folder name Raise empty script the Raise script didn't work and now the Ladder is not working either. But other scripts are working fine.  using System.Collections; using System.Collections.Generic; using UnityEngine;  public class Ladder : MonoBehaviour {     public Transform charcontroller;      private bool inside = false;     private float heightFactor = 3.2f;      private void OnTriggerEnter(Collider other)     {             inside = true;     }      private void OnTriggerExit(Collider other)     {             inside = false;     }      private void Update()     {         if (inside == true &amp;&amp; Input.GetKey("w"))             charcontroller.transform.position += Vector3.up / heightFactor;     } } Can I run PC steam games on a Mac? Why do the :before and :after pseudo-elements require a 'content' property? PrintWriter and PrintStream never throw IOExceptions At work we are being asked to create XML files to pass data to another offline application that will then create a second XML file to pass back in order to update some of our data. During the process we have been discussing with the team of the other application about the structure of the XML file.   The sample I came up with is essentially something like:  &lt;INVENTORY&gt;    &lt;ITEM serialNumber="something" location="something" barcode="something"&gt;       &lt;TYPE modelNumber="something" vendor="something"/&gt;     &lt;/ITEM&gt; &lt;/INVENTORY&gt;   The other team said that this was not industry standard and that attributes should only be used for meta data. They suggested:  &lt;INVENTORY&gt;    &lt;ITEM&gt;       &lt;SERIALNUMBER&gt;something&lt;/SERIALNUMBER&gt;       &lt;LOCATION&gt;something&lt;/LOCATION&gt;       &lt;BARCODE&gt;something&lt;/BARCODE&gt;       &lt;TYPE&gt;          &lt;MODELNUMBER&gt;something&lt;/MODELNUMBER&gt;          &lt;VENDOR&gt;something&lt;/VENDOR&gt;       &lt;/TYPE&gt;    &lt;/ITEM&gt; &lt;/INVENTORY&gt;   The reason I suggested the first is that the size of the file created is much smaller. There will be roughly 80000 items that will be in the file during transfer. Their suggestion in reality turns out to be three times larger than the one I suggested. I searched for the mysterious "Industry Standard" that was mentioned, but the closest I could find was that XML attributes should only be used for meta data, but said the debate was about what was actually meta data.  After the long winded explanation (sorry) how do you determine what is meta data, and when designing the structure of an XML document how should you decide when to use an attribute or an element? What is the difference between "is subject to" and "is subjected to"? I found the following sentence on the U.S. Customs and Border Protection website:     All persons, baggage, and other merchandise arriving in or leaving the   United States are subject to inspection and search by CBP officers.   I would like to know whether changing "subject" to "subjected" will change the meaning of the sentence. After Hoth, why did Vader pursue the Millennium Falcon instead of Luke's X-Wing? In The Empire Strikes Back film, the opening crawl says:     The evil lord Darth Vader, obsessed with finding young Skywalker, has dispatched thousands of remote probes into the far reaches of space....   It has also been established in Return of the Jedi that Force users can sense each other:     Chewie whines nervously. Luke stares at the Huge Super Star Destroyer    that looms ever larger before them.      LUKE: Vader's on that ship.   If Darth Vader is obsessed with finding Luke and he can sense his presence, the obvious thing to do would be to follow Luke's X-Wing after the battle of Hoth rather than the Millennium Falcon. Why didn't he? Following an earlier question ,  I would love to implement the  as suggested by Russell McMahon.   That way I could switch between 4AA batteries (1.2V*4 or 1.5V*4) and USB power. The battery voltage would nicely be regulated to 5V too. And the idea was to use the shutdown pin of the chip IF USB power is detected. The device also has to work when no batteries are present.  I am not too experienced with this, but I thought to connect the 5V from the USB to the SHUTDOWN pin from the LDO chip. Pitywise, the pin function is inverted, if SHUTDOWN is low, Vout from the LDO chip is low.  I am now considering using an XOR gate to make the thing work:         &ndash; Schematic created using   I would love to limit the amount of components, but the number of diodes is already high, and the whole thing feels a bit crafted   My questions:    Is there a better suitable chip (with an inverted shutdown pin) is there a better circuit (without voltage drop) to get this (I would prefer to get rid of D1, but then, the XOR has no desired operation) Keyboard layout indicator sometimes disappears Ubuntu 18.04.1 after some update How to allocate aligned memory only using the standard library? I just finished a test as part of a job interview, and one question stumped me, even using Google for reference. I'd like to see what the StackOverflow crew can do with it:  The memset_16aligned function requires a 16-byte aligned pointer passed to it, or it will crash. a) How would you allocate 1024 bytes of memory, and align it to a 16 byte boundary? b) Free the memory after the memset_16aligned has executed.  {        void *mem;    void *ptr;     // answer a) here     memset_16aligned(ptr, 0, 1024);     // answer b) here     } When I want to edit a tag of a question I get following message:     Your edit will be placed in a queue until it is peer reviewed.      We welcome all constructive edits, but please make them substantial. Avoid trivial, tiny one-letter edits unless absolutely necessary.   Now the question is: are tag edits (adding a needed tag to an under-untagged, replacing a mis-used tag) substantial enough?  For example the proc-tag-wiki is just about a Ruby feature called proc - but currenlty some questions about Oracle Pro*C (a embedded SQL preprocessor) or the Linux /proc filesystem are also tagged with proc. Btw, what tag should be used for /proc?  Say I come across a Pro*C Question which is tagged with proc - is a change to proc-sql considered substantial or not? How to customize the Ubuntu Live CD? I can't install or update Apps from Play Store: Error 905. How to fix? Suddenly (after a Play Store update?) I can't install or update any Apps. I always get error code 905 when I try to do so. How can I fix this? What did Bill do to make Hanzo mad? Quaternions, Rotations and Real numbers I haven't really formally studied Algebra at anywhere near this level, but I was told about the existence of Quaternions a few years ago and I find them really cool. I also like how pure quaternions are analogous to cross products in $R^3$, and that it gives me a way of doing it algebraically rather than relying on hand rules.  Over the course of using them it's my understanding that multiplying an element by another, both imaginary numbers, rotates it in some manner so as to be orthogonal to both, similar to rotations of $\frac{\pi}{2}$ in the space with one real and one imaginary axis when multiplied by $i$, which is why it's useful for cross products as it will rotate it to be orthogonal to a plane spanned by linear combinations of those two vectors [afaik].   What I can't intuit though is why for any pure quaternion multiplication, there's a negative real part [the scalar product] if it's meant to correspond to a rotation within $R^3$ and the space of pure Quaternions is Isomorphic to $R^3$. Similarly I don't understand why $i^2 = j^2 = k^2 = $ A negative real. Upper bound on $\chi(G)$ for a triangle-free graph I'm struggling with the following question;     For every graph $G$ such that $K_3 \not\subseteq G$ (i.e. $G$ does not contain a triangle), prove that $\chi(G) \leq 2\sqrt{n} +1$ (where $\chi(G)$ denotes the chromatic number).   Any hints? I really cannot see the connection between the triangle-free nature of $G$ and a chromatic number being bounded above by $O(\sqrt{n})$. Parse and Extract Attributes from JSON QThread and QTimer