Talk:Inductor/Archive 1

practical issue
It would be helpful, if l - length were better explained in formulas. I think it is the gap between the two walls of the coil form.

Also some examples of permeability ranges would be good.

I have decided I will have to resort to pulling a book off a shelf to make even a factor of 10 approximation for a coil. —Preceding unsigned comment added by 172.128.133.207 (talk • contribs)

it seems that some inductors use coil that is NOT electrically insulated - i.e. blank. i'd like to understand why the current will not chose the shortest path (through adjacent loops of wire, which touch one another) rather than going through every loop and building up the magnetic fied.


 * Most coils are wound with a wire with a varnish or polyurethane coating. Take and ohmmeter and you will see, it is really insulated wire. —Preceding unsigned comment added by 172.128.133.207 (talk • contribs)

secondly, would it not be most effective (in terms of maximum henries generated per volume of space occupied) to loop the wire in TWO countered sets of loops around the same core, which build opposing magnetic fields?


 * I think you'll find that what you see as bare wire is either separated by an air gap or a thin coat of paint. The voltage between turns is not that great so you don't need much insulation. Shorted turns is a common fault in motors, etc. Multiple layer inductors do exist, but I believe they are usually wound in the same direction to avoid some bad effects. More insulation is usually required between layers. --agr 13:29, 16 September 2005 (UTC)


 * Yes, winding wire as purchased is almost always insulated with a thin layer of varnish or enamel. Arnold is correct in that there are not usually many volts per turn, so a thin layer may provide enough voltage breakdown strength.

Regarding your second point, if alternate layers were wound in opposite directions, the magnetic flux would cancel out giving ZERO inductance. In fact, this is how some non inductive resistors are wound.--Light current 15:44, 16 September 2005 (UTC)

Category?
Why does Inductor belong to while Capacitor belongs to  ?--Astor Piazzolla 11:55, 14 December 2005 (UTC)

Typo?
Hi in the overview the word opposite appears -- do you mean opposes? — Preceding unsigned comment added by 165.247.104.133 (talk) 16:44, 18 December 2005 (UTC)‎

definition
In the equation for inductance you never say that L is inductance. If it's not, you need to say what it is.
 * Symbol added. Meggar 20:37, 19 December 2005 (UTC)

Inductance is the ratio of the back EMF induced to the rate of change of current. — Preceding unsigned comment added by 217.30.96.127 (talk) 13:03, 5 February 2006‎ (UTC)

Effect of one inductor on another
If there are two inductors connected in series in the same circuit and their mutual inductance is 0,can one inductor affect the flux through the other inductor in any way?-Subhash


 * That's not a homework question, is it? — Omegatron 13:17, 7 August 2006 (UTC)

Please give me a valid answer.I'm stuck up in a controversy related to this in the classroom and I want to know the fact.–Subhash
 * The question isn't really phrased "tightly" enough to answer. If the two inductors share (essentially) no flux (and so have essentially no mutual inductance), then they are independent components. The total inductance is the sum of the two individual inductors and the total impedance is the vector sum of the two individual impedances.


 * However, by adding its own contribution of L, R, and C into the series circuit, the second inductor clearly affects the flux developed in the first inductor and vice-versa; remove the second inductor and the flux in the first inductor will change (and vice-versa).


 * Atlant 13:21, 8 August 2006 (UTC)

Thank you for answering my question.Considering a pure inductor, what if the second inductor's current is suddenly diverted by the means of a switch when they(Both the inductors) have already reached(considering DC) steady state?That is, if the second inductor is somehow thrown out of the circuit after reaching steady state ,does the first inductor's flux or current get affected in some way(Considering 0 mutual inductance)?


 * Well, in the case of ideal inductors, your question isn't meaningful because, when connected to DC, our ideal, resistance-free inductors never will reach "steady state". So we'll put that case aside. ;-) For non-ideal inductors, instantly switching an inductor out of the circuit (that is, replacing it by a short circuit: a zero-resistance, zero-inductance path) will cause the remaining inductor to no longer be operating in steady-state conditions; you switched out some of the resistance in the circuit (the resistance of the non-ideal second inductor) so the current (and magnetic flux) in the remaining (first) inductor must then rise further until a new set of steady-state conditions are established.


 * Meanwhile, of course, the inductor that you instantaneously switched out of the circuit has thrown a heck of a spark as we instantaneously opened its circuit path, causing its terminal voltage to rise sharply as it tries to maintain the current flow. But tat's a topic for another discussion. ;-)


 * Atlant 12:10, 9 August 2006 (UTC)
 * Well, it's been a while so this might be a bit sloppy, but reactance (or some function of it) depends on inductance times derivative of current. At steady state, derivative of current is zero, therefore derivative of current times inductance is zero no matter what happens to inductance number two, including switching it out of circuit, i.e. dropping it to zero. If reactance of inductor number two doesn't change, then current through whole circuit will not change, drivative is still zero, so no effect on inductor number one. Gzuckier 15:37, 9 August 2006 (UTC)

Nutshell
So... in essence, an inductor tries to keep the current flowing at a constant speed...? (Please respond on my talk page.) tinlv7 23:02, 15 September 2006 (UTC)


 * I would rather say that an inductor keeps the current constant when the voltage at its connections is zero. To change the current you must apply a voltage. The other way: When you "tamper" with the connections, it creates voltages to keep the current going. LPFR 14:58, 10 October 2006 (UTC)

Formulas and approximations
As far as I recall, the formulas for conculating some inductance from some coil diemnsions are just approximations. With "typical" parameters, a lucky coil builder may get reasonably close results when winding his coil in real life, but he may appear to be less lucky when he designs his special 1.3 turn coil, whose parameters he verified with the mentioned formulas. Perhaps it should be noted which formulas are approximations and under which circumstances they provide reasonable results. Unfortunately, I have only vague memories on this topic, so I cannot help myself :-( --Klaws 15:33, 4 March 2007 (UTC)

Q Calculation
How about some way to calculate the Q of an inductor? The book "Reference Data For Radio Engineers" contains a graph that will give the Q for some solenoidal inductors. I was looking to calculate it or an air cored torroid, came here but NADA! Anybody know how to do this? (Yes, Iknow it's difficult!)


 * The Q is simply L/R (ratio of inductance in Henry and (DC) resistance in Ohm). Q depends on the frequency, so an inductor may have a different Q at a different frequency. The frequency dependent part can be major factor with, for example, ferrite core inductors. It is, if my memory serves me well, almost a non-issue in air-core inductors (the magnetic properties of Oxygen are very small compared to those of ferrite materials; note that the Wikipedia article incorrectly states that Oxygen is only paramagnetic is liquid and solid form - some physical gas detectors do in fact use the paramagnetism of oxygen). --Klaws 16:54, 4 March 2007 (UTC)


 * Q depends on frequency???. How so?  Does the L depend on frequency?  The R?  If so, then neither is an L or an R.  Yes, reactance depends on frequency but not L or R.  Alfred Centauri 04:21, 5 March 2007 (UTC)

Formulae units
Is it really necessary to have non-SI versions of some of the inductance "formulae"? This isn't standard practice on WP, and seems somewhat arbitrary. If people are working in imperial units, they can easily convert to SI before applying these equations. Oli Filth 18:25, 17 June 2007 (UTC)


 * No, we don't need these at all. Only commonly-used equations. — Omegatron 00:20, 18 June 2007 (UTC)

Help?
What's the average inductance of an inductor? Like, 1H, 5H? What would a 1H and a 5H inductor be used for? (Please respond on my talk page if you must.) tinlv7 18:29, 9 November 2006 (UTC)

There is no "average" inductance since the inductor value is always chosen depending on the task it is needed to complete. Since all tasks are different each task will have a different-sized inductor. Furthermore, inductors are usually very easy and cheap to make (just a wound loop of wire that doesn't even always need a core) so there is no need usually to standardize sizes. That being said, it is unusual to have one over 1 Henry in size. More likely you will be dealing with millihenries or microhenries. —Preceding unsigned comment added by 65.116.254.10 (talk) 21:08, 17 December 2007 (UTC)

current flow of an inductor
equation for current flow of an inductor at any given time passed the point at witch voltage was applied. Finding the current flowing in an inductor at any given time past when voltage was applied.
 * $$Amps = \left ( \frac{Vsource}{Rseries} \right ) * \left ( 1.0 - e ^\left ( -Time * \frac{Rseries}{inductance} \right ) \right )$$

$$e$$ is inverse natural log or normally $$e^x$$ on most calculators. This was removed for a unknown reason. I believe it to be common knowledge among ET and EE people so it was not cited. Eadthem (talk) 22:16, 31 July 2008 (UTC)


 * For a start, "amps" isn't a quantity, it's a unit! What's more the maths was badly formatted, and the more general formula is:


 * $$\ I(t) = I_0 ( 1 - e^{-\frac{tR}{L}})$$


 * This belongs with the material in the "In electric circuits", but it needs working into the existing text. I will do that shortly.  Oli Filth(talk 22:33, 31 July 2008 (UTC)

Inductance formulae
It would be super if someone adds figures next to each formula group so that people can see where are the variants (r,d etc.) exactly.--Infestor (talk) 09:18, 10 December 2008 (UTC)

Coil disambiguation
Just a layperson, trying to disambiguate coil -- should the currently non-existent induction coil be a separate article, or redirect here? or vice versa? Catherine 00:29 Apr 14, 2003 (UTC)

Why is "L" the symbol for inductance? - Joseph D. Rudmin


 * The "L" was chosen after Lenz's law. --Jeff Connelly 04:46, 30 November 2005 (UTC)

You mean the variable (The unit is usually Henrys.)? "I" was already taken for current; "i" for the square root of -1; not sure where L came from but I suppose it makes as much sense as anything. UninvitedCompany 19:49, 17 Feb 2004 (UTC)

Yes; how embarrassing! I know the difference between symbol and unit. I have corrected my question. - Joseph D. Rudmin

It's spelled characteristic.

Why did you move inductance to its own article? I think it is better in the inductor article with inductance as a redirect. They are essentially the same thing and should be in one article. Whether inductor or inductance I don't know, but the two belong together. That's like separating running from runner. An inductor (parasitic or otherwise), and nothing else, has inductance and inductance is a property of inductors. - Omegatron 16:58, Apr 13, 2004 (UTC)

At the very least, equations should be moved to inductance, and actual information on construction, etc. to inductor.


 * Why? They are both about the same thing.  A "parasitic inductor" is still an inductor, right?  And you don't construct those.  Maybe there is no such thing, and there is only "parasitic inductance"? - Omegatron 19:32, Oct 18, 2004 (UTC)


 * I guess to a physicist, inductance is more important than an inductor, and to an EE, vice versa...? Pfalstad 14:59, 6 October 2005 (UTC)

A CHOKE' is an inductor. An inductor is an electronic device. A CHOKE performs a specific task as does a TRANSFORMER, or the L in an LC circuit. The three are not necessarily interchangeable. A link from CHOKE to INDUCTOR could prove helpful. Morganbeaglemann (talk) 00:37, 11 April 2009 (UTC)

Straight wire conductor formula
Straight wire conductor formula for inductance contradicts itself.. :/ —Preceding unsigned comment added by 155.98.164.30 (talk) 23:24, 4 November 2009 (UTC)

wirewound resistors
Everything has some inductance. All resistors are non-ideal and have inductance. How could one test a resistor to see if it is ordinary wirewound, with some inductance, or special-wirewound with low inductance, or some other non-inductive type? What is typical inductance of various types of resistors? How much inductance is likely to be "significant" for various purposes? Does the inductance of a wirewound resistor tend to be more significant in low-ohms or hi-ohms resistors? -71.174.175.104 (talk) 23:44, 1 July 2009 (UTC)

Extended discussion of the inductance of wirewound resistors, and how to measure it: -71.174.175.104 (talk) 02:51, 3 July 2009 (UTC)
 * www.diyaudio.com/forums/showthread.php?s=&threadid=113209 * diyAudio Forums > Top >Loudspeakers >Loudspeakers >Resistor Inductance
 * According to the discussion there, many wire-wound resistors have surprisingly high inductance (with values in mH); this is negligible for low frequency, but critical in radio applications. -- Waveguy (talk) 04:04, 4 May 2010 (UTC)

cylindrical coil inductance formula is wrong
the formula does not include K the Nagaoka coefficient (im assuming they are using nagaoka's formula for single layer coil inductance), the formula should be:


 * $$L=\frac{\mu_0KN^2A}{l}$$

$$K$$ and $$\mu_r$$ are not the same afaik.


 * the Nagaoka coefficient offers a small correction; it is defined as K=1/(1 +0.9 r/a -0.02 (r/a)²) where r is the radius of the coil and a is the coil length. found after some digging at -- Waveguy (talk) 21:27, 21 March 2010 (UTC)

Shouldn't this equation use $$\mu_r$$ as well as K? this represents the situation where the core material is ferromagnetic.Glmory (talk) 22:41, 18 August 2010 (UTC)

I retract my statement, looking at the page for inductance, it is clear the situation is not as simple as that and going into more depth would just confuse matters more. However it should be made clear that the equation gives the inductance of a solenoid in air, not one with a ferromagnetic core. 192.212.253.17 (talk) 16:30, 19 August 2010 (UTC)

Units of inductor formulas
The units of many of the inductor formulas do not work out as they are currently written. The first and last appear to work out, but the units of the short air core cylindrical coil equation for example gives you micro Henries = inches. My guess is that the equations are correct, but are missing some units hidden in the constants. These should be explicitly shown.

Also the inductance page, and the inductors page should have their equations coordinated. They are giving very different equations.Glmory (talk) 17:16, 19 August 2010 (UTC)

Hydraulic Model
Sureley, a transformer could be modelled hydralically by having a pair of differently-sized "turbines" hooked together mechanically - running on the same shaft. One could even connect the two tubine shafts with a slippery clutch to model transformer losses.

Pmurray bigpond.com 03:19, 25 May 2006 (UTC)

Your idea is a great one but magnifying the voltage through induction is much more easier as well as efficient because there are no moving parts involved in a transformer.Besides when dealing with voltages as high as 750KV it is never safe to convert the electrical energy into mechanical energy.Subhash 04:53, 15 August 2006 (UTC)


 * Any way of modeling a transformer would be stretching the hydraulic analogy too far. Removed. Meggar 17:05, 19 August 2006 (UTC)
 * I'd like to remove the hydraulic model altogether - it seems contrived, and the effort you spend puzzling out the analog is better spent puzzling out how a magnetic field builds and collapses. --Wtshymanski (talk) 17:00, 19 August 2010 (UTC)
 * Well said. I second the motion to remove the hydraulic model altogether.  Wildbear (talk) 17:33, 19 August 2010 (UTC)
 * It's gone now. It seemed gratuitiously complex, since the mass of the flowing fluid would be sufficient, if you defind "mass rate of flow" to be like "current" and "pressure" to be like "voltage" and ignore the quadratic pressure drops across orifices....etc. Of course that doesn't let you explain mutual inductance. Some editors really like hydraulic analogies...--Wtshymanski (talk) 18:23, 19 August 2010 (UTC)

Reactor?
Is there any evidence that "Reactor" is actually used to describe inductors? I have never heard the term, but maybe it's like "condenser" - not used at all in some places, used in others. (Hard to do a Google search because of those big nuky things that blow up when a tsunami hits them...) Guy Macon (talk) 17:36, 13 April 2011 (UTC)


 * Yes, reactors are chokes. Google(inductor choke reactor) and you will get many hits sans nukes. See also saturable reactor. Glrx (talk) 17:50, 13 April 2011 (UTC)
 * In electric power transmission, it's usual to refer to "shunt reactors" meaning big air- or oil-insulated coils connected in parallel with loads, to regulate voltage; you also find "series reactors" usually used to limit short-circuit current. "Reactor" isn't used as much in the electronics industries. --Wtshymanski (talk) 18:26, 13 April 2011 (UTC)

"j is in ohms"
It says in the text "The impedance of an inductor (inductive reactance) is then given by:", then an expression, and then it's stated that "j is in ohms". Is this really true? Isn't j the imaginary unit, such that j^2 = -1, and isn't that unit always dimensionless? I think this is just a typo in the article, but I thought it best to seek consensus before editing, anyway. --Avl 08:24, 24 February 2006 (UTC)


 * Impedance can be a complex number. Take a look at the article for some more insight on that statement. ☢  Ҡ i∊ ff   ⌇  ↯  08:46, 24 February 2006 (UTC)


 * But the imaginary number is not in ohms. It's a number.  Does the article mean "j ohms"? — Omegatron 16:52, 24 February 2006 (UTC)


 * Yes, imaginary numbers have dimensions as well. It's always the same dimension as the real component.  I suppose you can debate whether or not they're real ohms, but then we are talking about an imaginary number, so I think that makes them imaginary ohms rather than real ohms by definition.


 * No, imaginary numbers do not have any dimension. The real component has no dimension, the imaginary component has no dimension. The sum has no dimension. Numbers are always just numbers. Constants, however, may have dimensions. Fatphil (talk) 13:14, 9 January 2012 (UTC)


 * I can't find what you're talking about in the article, so I'll just explain briefly. For a given frequency, an inductor will oppose the flow of alternating current similar to how a resistor would.  Whatever the formula was, it calculates this resistance.  (and it's important to note that, whatever the value is, it changes when the frequency of the AC changes)  It differs from real resistance in the way in which two resistances in series add together.  If you add together two inductance-style resistances, it's the same as adding together two resistance-style resistances, but when you add one of each, they add differently.  The way it works out is that you consider the resistor-style resistance a real component of the total resistance, and the inductance-style resistance an imaginary component, then add them together (which in this simple case is simply combining 10 ohms with 10 imaginary ohms to end up with a complex number like 10 + 10i ohms) and you calculate the effective resistance by finding the absolute value of this number (which is about 14 ohms in this case).  Interestingly, you can do the same with capacitors, but it is convention to assign capacitors negative imaginary values, since when capacitance-style resistance is added to inductance-style resistance, the two cancel eachother out.


 * I suppose it might be nice to put that in the article somewhere, but my writing style is so unencyclopedic. "Inductance-style resistance" isn't a real term -- I just made it up -- and all of this information is coming from a college textbook someone gave me which I threw away because I didn't like it, and thus I can't provide references. -- 24.209.110.27 (talk) 21:28, 18 July 2008 (UTC)

'i' is the mathematical symbol used for imaginary numbers. However, in electrical/ electronic context i or I is the symbol for current. Therefore j is used in place of i/I in electronic calculations. To save confusion between I current and i the 'imaginary root' of -1)

Thus, 10 + 10i ohms should really be written, for electronics use, as 10 + 10j ohms --220.101.28.25 (talk) 12:13, 24 October 2009 (UTC)

j is unitless, the unit for reactance, X, is in ohms. That way, when you say Z = R + jX [ohm] it makes sense. —Preceding unsigned comment added by 76.10.161.223 (talk) 00:56, 25 October 2009 (UTC)

Generalized Impedance
Why is there an equation only for impedance in the Laplace domain? Z = jωL is a pretty important equation, is it not? — Preceding unsigned comment added by 168.7.238.108 (talk) 17:57, 15 May 2012 (UTC)

the use of magnets
The authors had failed to notice is that in one of the images (called coils.jpg) [on the wikipedia page] shows an inductor with a magnet on it. i have scrapped a 17inch computer monitor (branded "acer") and i found two of these (heatshrink over the top). what is the function of the magnet? Charlieb000 (talk) 22:36, 5 March 2012 (UTC)


 * Why do you think that it is a magnet? The parts you found are most probably in the deflection circuits.  They are used to adjust the linearity of the scan.  By adjusting the magnet's position (usually part of the fatory's set up before being fixed in position), you alter the part of the B-H curve over which the inductor operates and consequently the linearity of the scan.   The magnet biases the core towards saturation and as the core does move toward saturation, it starts to behave less like an inductor.  DieSwartzPunkt (talk) 11:59, 16 May 2012 (UTC)


 * they were on the main pcb of the monitor. and i think i found the purpose of the magnets.... that a transformer that runs in contineous mode (always has magnetic field left in it) is able to provide a higher current. Charlieb000 (talk) 00:41, 19 May 2012 (UTC)

Error in Formula for Inductance of Straight Wires
Every reference I can find, e.g. http://www.ee.scu.edu/eefac/healy/indwire.html says that the inductance given by the straight wire formulas on this page are in nanoH not microH. Also, the argument of the log should apparently have a coefficient of 2 not 4. Somebody should confirm and fix this error. Brian Wowk (talk) 07:44, 22 August 2012 (UTC)


 * Well, Rosa was doing the work in cgs units, so the result would be in abHenrys. His 2 was changed to .2 to account for mm to cm conversion. And an abHenry just happens to be a nano Henry.
 * I took out the 0/3% precision claim because I didn't see a reference.
 * Glrx (talk) 22:46, 25 August 2012 (UTC)

Goddamn Wheeler and his inches
We should present the inductance equations in the SI form, foremost, since Henry is a SI unit and hell, this is a scientific article! These "easy equations for inches" created by some guy named Wheeler, apparently, are bastardized forms of the SI ones to make the use of inches easier and convenient. Yeah yeah, I know this is the English Wikipedia, so yadda yadda, but we need the SI equations in there, as they're the preferred and more scientific form.

The non-si equations could show up on a special section, even mentioning the Wheeler guy, describing how they were made up for convenience of imperial unit users, hence all the seemingly arbitrary constants. I'd do it myself, but alas, I don't have the equations, and that's also why I'm complaining. ☢ Ҡieff⌇↯ 21:37, 25 December 2005 (UTC)

I completely agree with these comments - it would be nice to replace the formulae with SI equivalents. Their source should also be referenced. Finally, there is a contradiction: the formula for a coil of thickness d does not tend to the formula for a thin coil in the limit d->0. As someone else has commented, if these are approximate formulae, their regions of applicability should be stated. Michael h seymour (talk) 09:43, 18 May 2010 (UTC)
 * And here it is nearly 5 years later and no apostles of SI have stirred themselves to post metric versions of the inductance formulas. Scientist use whatever system of units is handy, and if there isn't one, they'll make their own units. --Wtshymanski (talk) 19:59, 19 August 2010 (UTC)


 * For every devine's sake! The whole world uses the SI! Or would it be ok to change all inches to seamiles? Or imperial miles? Foot? Feet? I don't care if a farmer in the most outer long forgotten corner called the USA uses the imperial system! Sorry for my rage, but this is not America, nor the uk, this is a worldwide encyclopedia. — Preceding unsigned comment added by 212.115.198.155 (talk) 13:29, 28 September 2011 (UTC)
 * You shoulnd't make a system of measure your religion. The choices are all arbitrary, no matter how much significance you attach to the distance to the King's nose or how many wavelengths of krypton light to use. --Wtshymanski (talk) 14:34, 23 December 2011 (UTC)
 * Actually they are not arbitrary, they are international standards. That they became international standards was abitrary, but that is something decided long in the past. SI units now stand out uniquely as the lingua franca of engineering discourse. The presence of inches on this page is an embarassment.Fatphil (talk) 13:10, 9 January 2012 (UTC)

The issue here is not whether to use SI or some other unit system. The real issue is YOU SHOULD NOT MAKE EQUATIONS DEPEND ON THE CHOICE OF UNITS. (Sorry for shouting.) I've studied university-level physics in three countries, and only in the U.S. have I come across shit like "The area of a triangle is given by A = 216*w*h, where A is area in square inches, w is width in feet, and h is height in yards". In any other country, the formula is simply given as "A = w*h/2, where A is area, w is with and h is height" and you are free to use whatever units you like.

If you take the (correct) formula $$L=\frac{\mu_0KN^2A}{l}$$ and use either inches or meters, you get the same answer. You can also deduce the unit of L from the units you input. If you take the (incorrect) formula $$L=\frac{r^2N^2}{8r+11d}$$ it doesn't really matter what units you use. L will come out in units of length, not inductance. It is possible that the original reference is correct (I haven't checked) but whoever copied it into the article failed to include the symbol $$mu_0$$. In that case, the formula will work regardless of unit system. Or it could be that these formulae only work with a carefully chosen set of units, in which case they are worthless and need to be converted to a useable form. PeR (talk) 15:13, 13 January 2012 (UTC)
 * (months later) Of course systems of units are arbitrary. That's why they are so hard to define. And the closer you look, the more arbitrary they become. How long is a day, for instance? And in the CGS units system, capacitance has units of length, resistance of velocity, and I can't recall what the units of inductance were but I bet it's equally surprising. --Wtshymanski (talk) 15:51, 18 September 2012 (UTC)

Тhе abbreviation Kool Mu MPP
Tell me please, what does this mean in the sentence "Toroidal core coils are manufactured of various materials, primarily ferrite, Kool Mu MPP, powdered iron and laminated cores."? Д.Ильин (talk) 15:31, 11 December 2012 (UTC)


 * Removed now. I dug through history, and it was introduced back in 2010, as "Koom Mu® MPP", apparently as an advertising for an Indian producer of electronics. A vandal changed it to "Kool" in the meantime. Thanks for your awareness, we seem to be lacking careful readers these days... or years. No such user (talk) 16:06, 11 December 2012 (UTC)


 * OK. Thanks. Д.Ильин (talk) 16:43, 11 December 2012 (UTC)


 * MPP is a common core material designation; I believe it stands for molybdenum permalloy powder. The cores are pressed from the power and then sintered. Different core permeabilities may be achieved by using more binder. The "Kool Mu" part would be trade name advertising low loss and would be irrelevant for the article. Glrx (talk) 20:51, 14 December 2012 (UTC)

Stored Energy
It'd be super-awesome if someone could make the section on stored energy look similar to the section on stored energy in the article about capacitance. Over there, I think it makes it easy to understand why the equation is what it is, whereas here, I'm left wondering why it is what it is. It's very symmetrical, so I'm sure it's correct, I'm just having a difficult time understanding how one determines "the amount of work required to establish the current through the inductor" which would be awesome information to have. -- 24.209.110.27 (talk) 21:36, 18 July 2008 (UTC)


 * I think the key to understanding this is to turn around the definition of a henry. The standard definition is "an inductor with an inductance of 1 henry produces an EMF of 1 volt when the current through the inductor changes at the rate of 1 ampere per second."  In equation form this is H = V / ΔI, indicating that the value assigned to inductance increases when the EMF voltage increases, and decreases when the current required to create this voltage increases.  To make this easier to understand, just rearrange it to ΔI = V / H, which indicates that the change in current increases with applied voltage, but decreases with increased inductance.  This makes the whole issue of inductance a lot easier to understand.  Want to know what happens when you apply 5 volts to a 1 mH inductor?  Well, 5 / 0.001 = 5000, so the current increases at a rate of 5000 amperes per second when 5 volts is applied to this inductor, at least until your power supply fails.  Needless to say, such voltage is always applied to such inductors for very short periods of time, or via resistors which will cause the applied voltage to decrease as the current increases.


 * So anyway, imagine you apply one volt to an inductor of one henry. Over time you will see a linear increase in current, rising to one ampere after one second, and two amperes after two seconds.  Since power equals voltage times current, we can calculate the power going into the inductor at any moment.  At one second it is one watt, at two seconds it is two watts, and this can be integrated to end up with the equation in the article.  If you don't want to integrate, just draw a graph (linear graphs are easy) and shade the area under the line to represent the stored energy.  After one second, you have half a shaded square.  After two seconds, you have two shaded squares.  After three seconds, you have 4.5 shaded squares.  All which are the same values given by the formula in the article.


 * I suppose this too would be nice for the article, but I kind of just made it all up. The way that calculus is written makes absolutely no sense to me, so I've kind of had to figure out stuff like this on my own.  I can't seem to find a reference that doesn't use standard calculus notation and so I'm not sure anything actually agrees with me.  All I know is that when you integrate y = b * x, you end up with 0.5 * b * x ^ 2, which leads to the equation in the article.  --  The one and only Pj (talk) 02:57, 21 July 2008 (UTC)

I quote the sentence from stored energy: "The energy (measured in joules, in SI) stored by an inductor is equal to the amount of work required to establish the current through the inductor, and therefore the magnetic field. This is given by:" and it gives the formula.

In the above, stored energy is equal to (the same as) the amount of work. I am assuming that this is only true for an ideal inductor. If it was a real inductor with real DC resistance, the amount of work required, in other words the power, or product of the volts and amps input into the inductor would be more than the amount of energy stored in the magnetic field because there would be some loss in the DC resistance of the wire, and some amount in heating of the core. So it seems to me that the stored energy is not equal to, and less than the amount of work. Am I correct in this assumption? If I'm not, does the quote above need further explanation? Thanks. 208.127.16.41 (talk) 10:18, 16 April 2013 (UTC)
 * The ideal inductors are in the physics lab stock room, between the frictionless planes and the black-body radiators. It's a very common trope in physics explanations to give the ideal, zero-order approximation first and then complexify it with all the losses. F hardly ever equals MA in the real world, but that's the way it's taught in the lecture hall. In fact the great genius of people like Newton or Ohm is *seeing* the very simple equation that idealizes the behavior of all those messy experimental measurements, complete with error bars.  --Wtshymanski (talk) 17:50, 16 April 2013 (UTC)

Merge Electromagnetic coil into this article?
The stuff in electromagnetic coil looks mostly either redundant or irrelevant. --Pjacobi (talk) 19:20, 22 September 2008 (UTC)


 * I'm surprised such an article exists. It is the same thing as an inductor.  Maybe it can have its own section on this page.  Its list of Core examples is useful though.   Liuyuan Chen  23:52, 23 September 2008 (UTC)


 * I agree, it should be merged into this article. -- Chetvorno TALK 05:19, 24 September 2008 (UTC)
 * NOT AGREE ! Electromagnetic coil → de:Spule (Elektrotechnik)
 * Inductor → de:Induktanz
 * clean up the articles.--Staro1 (talk) 09:09, 6 November 2008 (UTC)
 * I do not agree —Preceding unsigned comment added by 85.73.129.186 (talk) 03:52, 2 October 2010 (UTC)

The articles Choke (electronics), Induction coil and to some extent Induction loop all refer (as far as I can see) to the same object, an inductor. I do not understand the reference to the two German articles, one about a component (a coil) and one about a physical phenomenon and basic unit (Inductance). --Thorseth (talk) 10:48, 27 February 2009 (UTC)


 * An Induction coil is a type of transformer, combined with a vibrating interrupter switch. Clearly not a simple inductor. The "Induction loop" was (according to the article) a communications system, referring to the amplifier as well as the wire loop.  In my view Choke (electronics) could go either way; its a specialized type of inductor, perhaps different enough from other inductors to merit its own article.  However electromagnetic coil is a mere generic term for a coil of wire, that could refer to an inductor or a solenoid or perhaps a Helmholtz coil, so I feel it's too broad to have its own article and should be covered in those existing articles.  Maybe the German term "spule" has a more specific meaning, but in English it is simply a coil of wire.  -- Chetvorno TALK 19:08, 27 February 2009 (UTC)


 * Concur with Chetvorno, induction coil is more than a simple inductor. This specialized device merits its own page.  The merge sugestion has been removed from both articles. Armstrong1113149 (talk) 19:14, 1 March 2009 (UTC)


 * Induction loop is an independent topic about a communications device and should not be merged with inductor. Julianpieters (talk) 13:55, 24 June 2009 (UTC)

I think the reason people try to merge different things into one is an absence of understanding the difference, which is the HUGE GAP between a "perfect mathematical inductor", defined by the familiar differential equation and the REAL devices, working by absolutely different principles. BTW, most electronics articles refer to simplifies (not to say stupidified) mathematical models, while absolutely ignoring the real world components and their application in real world circuits. No fun... :( Neonil (talk) 13:05, 5 May 2009 (UTC)

I think it's clear that the merger proposal should be removed, because inductor is not a coil and vice versa. Neonil (talk) 13:44, 5 May 2009 (UTC)


 * It seems to me that Neonil's issue is irrelevant to whether electromagnetic coil should be merged. All inductors depart from their ideal circuit models due to resistance, parasitic capacitance, leakage flux, magnetic saturation, hysteresis, etc.  This article deals with both the ideal circuit model and construction of real inductors.  I agree it doesn't include enough about the above real world effects, but this should be fixed by adding to this article. -- Chetvorno TALK 17:08, 11 June 2009 (UTC)

In relation to merging the article Choke (electronics) with the article inductor, leaving aside the technical differences discussed above, as a user I feel it should not be merged on the basis of common usage - the term choke is widely used in engineering and industry for this type of device, and my personal view is that it warrants its own article despite being part of a wider group of technically similar devices. —Preceding unsigned comment added by 78.151.216.78 (talk) 11:18, 5 July 2009 (UTC)

Absolutely merge "choke" into "inductor". A choke is simply another term for inductor, and is somewhat archaic. It is what condenser is to capacitor. The content should be merged into inductor. As for "electromagnetic coil", that is a description, not a name. 71.129.86.9 (talk) 20:08, 15 February 2010 (UTC)

''A choke is a principle involving an inductor to serve a purpose, while an inductor is a catch all for nearly any component utilizing a coil of wire to create an electro-magnetic field. While, yes, a choke is an inductor, it is also a separate and distinct use for an inductor such as a transformer or generator in their respective and most basic form. —Preceding unsigned comment added by 208.102.255.184 (talk) 01:16, 29 July 2010 (UTC) ''

DO NOT MERGE. The common mode choke is NOT an inductor. It is not use to store energy but to transform energy in heat. The unwanted common mode current is then dissipated. I will provide more datas in a couple of week on this topic. —Preceding unsigned comment added by 194.105.120.80 (talk) 08:02, 23 September 2010 (UTC)

Bad spot in the intro
The intro asserts that "Due to the time-varying magnetic field inside the coil, a voltage is induced." But that sentence leaves the innocent reader asking himself, "What time-varying field? Who said anything about the field's varying over time? Why should it vary?"

I request that somebody who knows what he's talking about do something appropriate to fix that passage.—PaulTanenbaum (talk) 03:00, 3 February 2012 (UTC)
 * See Talk:Inductance for the biggest mess since Talk:Decibel, Talk:Wavelength or even Talk:Speed of light. Warning - contains adult themes and situations, not for the idealistic. --Wtshymanski (talk) 18:00, 15 May 2012 (UTC)
 * The sole reason for the 'mess' as you call it is because of your continued pointless and largely irelevant input. If you distil the discussion down to those comments that are relevant to the issue being discussed, there are not more than 8 to 10, a not unreasonable quantity.  Everything else is your irrelevancies designed to hide your total lack of knowledge and the responses thereto. 86.169.33.6 (talk) 09:14, 16 May 2012 (UTC)


 * Inductors as a component are only used as such in AC circuits where the varying current produces a time varying field. Although you could include an inductor in a DC circuit, there would be no point as it would only function as a resistor.  The one (vaguely) counter example is the use in power supply circuits in the flter section.  But even here it is the effect of the AC superimposed on the DC that is of interest.  The inductor here is a higher impedance to the AC (due to the reactance to the AC) than it is to the DC.  Although wound electromagnets and DC motor field windings are technically inductors, they are seldom refered to as such and the inductance is rarely, if ever, used to calculate the magnetic properties. 86.169.33.6 (talk) 09:14, 16 May 2012 (UTC)


 * I agree with PaulTanenbaum that this is confusing for many readers. The cause of the confusion is the first sentence: "An inductor... is a...electrical component that stores energy in its magnetic field".   General readers unfamiliar with electronics get the idea that the inductor is an energy storage device like a rechargeable battery.  So why should time-varying fields be so important? -- Chetvorno TALK 17:50, 7 May 2013 (UTC)


 * Rewrote introduction to address PaulTanenbaum's complaint, correct a lot of other shortcomings of existing intro, and expand to make it an adequate summary of the article as required by WP:INTRO. -- Chetvorno TALK 01:04, 24 August 2013 (UTC)

Need images
This article has plenty of pictures of small inductors used in consumer electronics, but desperately needs some pictures of the high Q RF inductors used in the tuned circuits of radio transmitters. I'm thinking of images that show the construction techniques used for high Q coils: air core single layer coils with the turns separated, perhaps high-power ones made of tubing to reduce skin effect losses. Also modern images of variometers, spiderweb coils, and the thick litz wire coils used in LF transmitters would be great. Commons doesn't seem to have any recent images of this stuff. The only image of an air core RF coil in the article now is an out-of-copyright one I downloaded of an "oscillation transformer" from a 1922 spark gap transmitter! Can anyone help? -- Chetvorno TALK 02:45, 24 August 2013 (UTC)

About removing formula in section "Stored energy"
I removed the sentence and formula below in section "Stored energy"

That we have
 * $$\begin{align}

P(t) &= V(t)I(t) = I_L(t)L\frac{dI_L(t)}{dt} \\ I_L(t) &= I_L(\infty) + [I_L(t_0) - I_L(\infty)]e^{-\frac{1}{\tau}(t - t_0)} \\ I_L(t) &= I_m(1 - e^{-\frac{1}{\tau}}) \end{align}$$

where
 * $$\begin{align}

\tau = \frac{L}{R} \\ I_m = \frac{E}{R} \end{align}$$

Because i can't see the relationship between this formula and the energy stored from t0 to t1. The R is not mentioned in the formula of stored energy.--Wolfch (talk) 12:50, 15 November 2013 (UTC)


 * $$E = \frac{1}{2}LI_o^{2}(1 - e^{-\frac{1}{\tau}})$$

Actually you're right. It should be in RC section. That formula was still incorrect either way. What I just posted is the natural response of an RL circuit within the power formula an integrated from 0 to t. It will be moved. There should be a see also inline template for the equations section so people will find correct formulas since there are many inductor articles.—CKY2250 &tau;&alpha;&iota;&kappa; 14:47, 15 November 2013 (UTC)

Discussing Removal of Inductor Equations
Below are additions I placed in the 'circuit theory' section that were recently reverted. Please feel free to share your honest opinion so that we can reasonably decide the fate of this material. Thanks. For now, I will put it up until otherwise argued against because I believe its correct-->

An inductor connected to a sinusoidal voltage source has a current:


 * $$ I = \frac{1}{L} \int V \,dt$$

In the case that this source voltage is V0cos(ωt), the current through the inductor is:


 * $$ I = {\frac{V_\text{0}}{\omega L}}{\sin{(\omega t)}}$$

At sin(ωt) = 1, the maximum (or peak) current flows through an inductor.

In the case that this source voltage is V0cos(ωt), the current through the inductor is:


 * $$ I = {\frac{V_\text{0}}{\omega L}}{\sin{(\omega t)}}$$

The ratio of peak voltage to peak current resembles inductive reactance (denoted XL), which causes the inductor to have a self-induced backward current that flows against the forward current.

XL goes to infinity as ω approaches infinity. If XL goes to infinity, the inductor resembles an open circuit that poorly passes high-frequency signals. On the other hand, XL goes to zero as ω approaches zero. If XL goes to zero, the inductor resembles a short circuit that strongly passes low-frequency signals.

I also wanted to add the following -->

The current may be expressed in the form of cosines to better compare with the voltage of the source:


 * $$ I = {I_\text{0}}{\sin({\omega t}}) = {I_\text{0}}{\cos({\omega t} - {90^\circ})}$$

This helps explain a statement already in that section, which says "In this situation, the phase of the current lags that of the voltage by π/2."

The voltage can also be approximated by using the following equation:


 * $$V = N{d\Phi \over dt} \, = \frac {l} {dI \over dt} \,= L{dI \over dt} \,$$

where µ is the permeability of the material on which the coil is wound, N is the number of turns of the coil, A is the cross-sectional area of the coil, and l is the length of the coil. In free space, µ = µ0 = 4π x 10-7 N/A2

BatManFascination (talk) 01:02, 1 February 2014 (UTC)


 * As it appears to me, these equations are correct and very important, so I put them back up. JaunJimenez (talk) 02:02, 1 February 2014 (UTC)


 * I have lots of comments:


 * 1) I share concerns raised by Chetvorno and Spinningspark about adding unnecessary equations and also about mixing capital and lower case letters.  One good convention is that capital letters refer to (constant) amplitudes while lower case refers to time-varying parameters.
 * 2) We also have to agree on whether to use $$f$$ or $$\omega$$.  Pick one and use it in ALL the equations, and perhaps mention in the prose that $$\omega=2\pi f$$
 * 3) JaunJimenez and BatManFascination both want a few more equations, and they have a valid point.  We just need to be consistent in our notation and avoid too much repetition.

(forgot to sign -- --guyvan52 (talk) 04:08, 1 February 2014 (UTC) )


 * Yes, that's right, my objections were mainly on the grounds that these edits made a mess notationally, in particular, confusing instantaneous, peak and RMS variables. However, a lot of it is also simply repeating what is already in the article in a slightly different form.  There are always numerous ways of presenting equations and explaining phenomena.  We shouldn't endlessly add new variations just because it is the favourite of an editor or happens to be the form in their textbook.  This just puts readers off the article.  If a different form would be better, this should be discussed here first rather than arbitrarily changing the article.
 * I also think the statement that the ratio of peak voltage to current is due to reactance is troublesome. Not really, that is just the definition of reactance (I would have preferred RMS, but that involves introducing yet anther concept into the article).  I agree, however, that this article could usefully have something on reactance.  I have created a separate subsection for it so that it does not get entangled in the time-domain analysis.  Hopefully, it addresses the points above.  Spinning  Spark  10:25, 1 February 2014 (UTC)


 * On the $$f$$ v. $$\omega$$ question, I think that it is a good principle to use the more familiar $$f$$ in basic articles and move to $$\omega$$ where there is more complex analysis or the article is mathematical in nature. On a related note, I don't see the value of the s-domain section in this article.  It is a pretty useless analysis for a single element.    Even the $$j \omega$$ domain would be more appropriate.  Laplace transforms only even start to be helpful in circuits where there are at least two elements such as LR circuits.  Spinning  Spark  15:35, 1 February 2014 (UTC)


 * Thanks for your input. So, at this point, how should we resolve the issue while avoiding a stalemate. I still hold the belief that there is valuable "unique" information in my edits that deserve to be on the page. Moreover, I think it is important to express an equation in various forms to help said reader more easily understand and solve a problem on inductors. In regards to the correct wording in some locations (such as 'due to'), I do agree that it can be worded better. Also, on reflection, I agree that the equations could be placed in better  locations. Could you please explicitly tell me the notational forms you would like me to use ? I think it would greatly help to resolve the issue. Thank you. BatManFascination (talk) 20:09, 1 February 2014 (UTC)
 * There is now a section on reactance, the formula you wanted to add for calculating inductance is already in the list of formulae and I have added an explanation of when K can be put to one, a note about phase has been added. The integral form of the constitutive equation is just a rearrangement of the differential form.  Besides all that, what else is there that you think should be added to the article?  Spinning  Spark  20:17, 1 February 2014 (UTC)
 * Please stop tinkering with your initial post. Several people have now replied to it, and the conversation will start to not make sense if you make substantial changes.  Spinning  Spark  20:21, 1 February 2014 (UTC)


 * Ok. You're right This inductance equation you speak of is different from the voltage equation I put up though. Also, I put back the initial post. Thought it would be helpful to take down that which we knew shouldn't be used. Below is material I still think deserves a spot. What do you think should be on the page (if any)? -->


 * $$V = N{d\Phi \over dt} \, = \frac {l} {dI \over dt} \,= L{dI \over dt} \,$$


 * The current may be expressed in the form of cosines to better compare with the voltage of the source:


 * $$ I = {I_\text{0}}{\sin({\omega t}}) = {I_\text{0}}{\cos({\omega t} - {90^\circ})}$$


 * This helps explain a statement already in that section, which says "In this situation, the phase of the current lags that of the voltage by π/2."


 * An inductor connected to a sinusoidal voltage source has a current:


 * $$ I = \frac{1}{L} \int V \,dt$$


 * At sin(ωt) = 1, the maximum (or peak) current flows through an inductor.


 * In the case that this source voltage is V0cos(ωt), the current through the inductor is:


 * $$ I = {\frac{V_\text{0}}{\omega L}}{\sin{(\omega t)}}$$


 * The ratio of peak voltage to peak current resembles inductive reactance (denoted XL), which causes the inductor to have a self-induced backward current that flows against the forward current.BatManFascination (talk) 20:41, 1 February 2014 (UTC)
 * I think Spinningspark's version summarizes the essential information better, and that's all that is needed.  The JaunJimenez version is confusing and overexplains.  Specifically:
 * $$V = \frac {l} {dI \over dt} \,$$ is already in the "Inductance formulae" section. This is not a fundamental formula but only applies to a specific form of inductor (an open ended coil of wire).
 * There is no need to say that the maximum of sin(ωt) is 1; we are assuming readers are familiar with trigonometry.
 * The integral form of the inductor equation is unnecessary
 * JaunJimenez has a point that the current Reactance section only explains the magnitude of the reactance and doesn't mention the phase angle (although this is derived in the previous section). However, if this is to be included I think the right way would be to derive the complex reactance $$X_L (j\omega)$$, which is how it is usually used in engineering.
 * The explanation of inductive reactance as a "self-induced backward current" is erroneous; there is no backward current, just an induced voltage that opposes the forward current.
 * I agree that the notational inconsistencies are unacceptable (using uppercase I for instantaneous current and ω insetead of f as used in the rest of the section).
 * -- Chetvorno TALK 22:16, 1 February 2014 (UTC)
 * Gotcha. Thanks a lot for clearing that up. JaunJimenez (talk) 22:31, 1 February 2014 (UTC)

Direct Current Current
"Inductors are used as the energy storage device in many switched-mode power supplies to produce DC current." It's just "DC" not "DC Current". — Preceding unsigned comment added by 86.181.235.235 (talk) 16:16, 22 December 2013 (UTC)
 * While you are technically correct, electrical engineers routinely refer to 'AC current' and 'DC current' to distinguish the two types of current. They also routinely refer to the even more technically inaccurate 'AC volts ' and 'DC volts '.  Indeed the range switch of nearly all multimeters are marked 'ACV' and 'DCV' or 'AC volts' and ' DC volts' or something similar.  85.255.233.66 (talk) 09:32, 5 March 2014 (UTC)

Lenz's Law (re)wording
Currently [| the paragraph] reads


 * "The energy from the external circuit necessary to overcome this potential "hill" is stored in the magnetic field of the inductor; the inductor is said to be "charging" or "energizing"."

My problem is that this sentence begins in the past tense - "is stored" - and ends in future tense. I think it could possibly be argued that the first half of the sentence has no definite, or at least an ambiguous, tense, so that it's not actually grammatically incorrect, but it certainly took me a while to wrap my head around what the sentence was trying to say.


 * "The energy from the external circuit necessary to overcome this potential "hill" is being stored in the magnetic field of the inductor; the inductor is said to be "charging" or "energizing"."

I realise that the second version doesn't read quite as well, but the tense is definite and correct, and I think clarity is prose more important than aesthetically pleasing prose in an encyclopaedia. The sentence could definitely be re-written, but I thought it best to make the point as to why I think the current version could be improved.

I'm going to undo the undo. I'm new at the intricacies of Wikipedia editing so I hope this causes no offence/issue, it just seems like the reasonable thing to do to make the point. I was going have another go at a re-write but I think I'll let other interested parties respond first. Maybe I'm the only one who finds the current wording confusing.

Worp8d (talk) 09:57, 9 September 2014 (UTC)


 * Is "is stored" really the past tense? Past tense would be "was stored". The word you have inserted adds nothing to the meaning and subtracts from the clarity. Spinning</b><b style="color:#4840A0">Spark</b> 11:12, 9 September 2014 (UTC)

Nonlinearity
Spinningspark, did you take a look at Linear circuit? It defines both linear and nonlinear circuits (sort of like Near and far field), mentioning saturated inductors. I think it would be a more informative link than the more general Nonlinearity, although I'm fine with either one. -- Chetvorno <i style="color:purple; font-size:smaller;">TALK</i> 19:20, 23 April 2015 (UTC)


 * Yes, I'm aware, but readers following the link will arrive at the top of the article and will most likely be quite baffled. A better solution would be to create nonlinear circuit and make it a redirect for now to a specific section or subsection in linear circuit.  It would be necessary to put in a sub-heading or anchor point in the article to do this effectively, but I don't think that's a major problem to do. <b style="background:#FAFAD2;color:#C08000">Spinning</b><b style="color:#4840A0">Spark</b> 19:33, 23 April 2015 (UTC)

Thanks to the author(s) from the Tatar Wikipedia participants
Thank you, the author(s) of this article. We translated your article into the Tatar language.--A.Khamidullin (talk) 12:36, 26 March 2017 (UTC)

Section 5.4 Stored Energy
I'm not an expert but I do have concerns about this section.

I agree with the first part of this section, right up to "This relationship is only valid for linear (non-saturated) regions of the magnetic flux linkage and current relationship."

The remainder "In general if one decides to ..." seems to have a mistake. It should also be in another paragraph (since the previous sentence is a condition of the formula above it). The "In general..." part is just a generalization of the prior text.

Complaints:

In the integral, the use of P has not been defined in this article at all. I am not fully versed in all the different formulas for inductors (especially integrals) so I can only assume P=power in watts (joules per second). How is this derived? Is it the voltage across the inductor times the current through it at a point t in time?

Also, why the use of the term "LTI"? This first time appearance in this article made me google what LTI stood for: "Linear Time Invariant". What the heck does that mean? So, now to fully understand what an LTI inductor is, does that mean I have to understand LTI theory before I can grasp the concept of an LTI inductor and thus continue? Or would it have been simply better to replace the use of "LTI" for the word "unsaturated"? After all, the following generalization comes from the previous formula that specifically states the conditions.

The mistake: The equation for E does NOT allow us to "find the energy stored in a LTI inductor that has initial current in a specific time between t(0) and t(1) ..." Rather, it is the NET CHANGE in energy E. This is an important distinction.

The right hand side: 1/2 LI(t1)^2 - 1/2 LI(t0)^2 is the NET CHANGE in E (delta E)

The integral, if I worded the definition of P correctly, seems to also imply the net change.

Thus, "E =" should be "delta E =" and the text rewritten to say "In general if one decides to find the net change in energy stored in a inductor (operating in it's unsaturated region) in a specific time between t(0) and t(1) can use this:"

Notice I left out "has initial current" as this would be spelled out in the formula. Besides, it has an initial voltage too. A chosen L, etc.

Jotdot (talk) 10:31, 25 February 2016 (UTC)
 * Yo, you're just spot on. This small section is woeful.  Like just where did that initial formula for 'E' come from? I think it should be $$E = \frac {1}{\sqrt 2}LI^2$$   (ha, ha! just kidding, but who says?  Maybe I'm right).  My point is, it's unsourced.  There's nothing scholarly about this section; no mention of what happens when you cut off current to an inductor (hey, dude, you smell something burning?).  Considering everything needs done here, we don't need to go into any meta-theoretic LTI stuff.  I'm gonna do some basic cleanup here.  I'm not an expert, but I been doin' this a while.  Sbalfour (talk) 21:11, 21 November 2017 (UTC)


 * Rewrote section to try to make explanation a little clearer.  Added supporting citations. -- Chetvorno <i style="color:purple; font-size:smaller;">TALK</i> 20:54, 22 November 2017 (UTC)
 * Citations extremely welcome. This section quite well done now. Thanks. Sbalfour (talk) 21:10, 22 November 2017 (UTC)

Applications section
It says, An inductor connected to a capacitor forms a tuned circuit,. NO, it doesn't. I invite someone to take my bins of capacitors and inductors, pluck any pair out, and give it a try. Heck, pluck out a dozen each and mix and match. We're talking about an AC circuit at a particular frequency here (like a radio frequency of interest); most of my cheap capacitors are electrolytic, so I hope whoever tries this is supervised by a competent professional. Inductors are used in power supplies... with filter capacitors remove residual hums known as the mains hum. Hmmmm...  I checked several linear power supplies, and the frequency analyzer doesn't show any 60hz fundamental output from the rectifier just before the filter. That means I don't need those inductors or capacitors? Where's that 60hz hum I'm supposed to eliminate? Maybe the statement means this one: the hum. The efficiency of a transformer may decrease as the frequency increases Generally, the efficiency of a transformer increases with frequency. Before standardization, that's the reason electrical power distribution was mostly 133-1/3hz. This whole section is seriously bad. Sbalfour (talk) 19:08, 22 November 2017 (UTC)
 * Gently, gently. Doesn't say what frequency the circuit is tuned to, and your 1 Farad 'lytic with a 1 inch piece of wire across the terminals is still an LC tuned circuit, though maybe not a useful one. An inductor or choke coil was  a pretty common component of filters in old-timey radios, back when an electolytic capacitor cost more than a 3 course meal - some ole electrodynamic speakers used the speaker field coil as the power supply filter choke.  Maybe not 60 Hz, but some harmonic of the power frequency. Was 133 1/3 Hz ever run for miles along the road or was it just for isolated lighting plants in a building? --Wtshymanski (talk) 20:32, 22 November 2017 (UTC)
 * Yes, Sbalfour, keep in mind that Wikipedia is an encyclopedia for general readers who may not have any electronics knowledge. We want to ease into complicated topics and not just hit them with everything at once.   "An inductor connected to a capacitor forms a tuned circuit" is a correct definition.    And preventing "hum" (or ripple) on the output of a rectifier power supply is the entire reason for using an output filter; otherwise the electrolytics would not be needed. -- Chetvorno <i style="color:purple; font-size:smaller;">TALK</i> 20:51, 22 November 2017 (UTC)
 * Of course, I know these things. When I design a tuned circuit, I know what I'm tuning to, so a very specific capacitor/inductor pair is required, not just any pair.  For an inexperienced hobbyist with a breadboard, obtaining a tuned circuit is a very practical matter - it depends on what frequency is available from his power supply, or circuit.  Then he might or might not have an appropriate inductor/capacitor available - he can't just use any pair. And I don't care about the mains frequency at all in power supply filtering - it's not there.  In a SMPS, the most familiar kind, the frequency(s) of concern are quite high.  So I think we need to say something a little more relevant. Sbalfour (talk) 21:08, 22 November 2017 (UTC)
 * Okay, well, how about: "A tuned circuit consists of an inductor connected to a capacitor". That way we're not implying that any inductor and capacitor together make a practical tuned circuit.  However I really don't think the previous sentence is going to mislead anybody. -- Chetvorno <i style="color:purple; font-size:smaller;">TALK</i> 23:45, 22 November 2017 (UTC)
 * Ahhhhh... time to move on. Sbalfour (talk) 00:00, 23 November 2017 (UTC)

A transformer is an inductor?
I have reservations about this sentence added to the introduction: "A transformer is a special kind of inductor...". While mutual inductance is usually introduced with self-inductance in electronics and physics books, transformers and inductors are considered different components in the electronics industry. This sentence will be confusing for general readers because although they may look similar, these two components do completely different things. A transformer is a two-port component that converts electrical energy applied to one port to a different voltage at the other port, while an inductor is a one-port component whose purpose is to resist changes in current. Is there a source for this statement? I couldn't find any source which says a transformer is a type of inductor. -- Chetvorno <i style="color:purple; font-size:smaller;">TALK</i> 02:05, 23 November 2017 (UTC)
 * That was my addition. I'll remove the statement, and defer to your judgment.  I was thinking of the case of aligning two inductors and throwing them into a box - it'd be a transformer (not a good one).  The statement will eventually move into the Mutual inductor section, in a way similar to the statement that a capacitor and inductor form a tuned circuit... two inductors coupled with mutual inductance form a transformer. Sbalfour (talk) 17:16, 23 November 2017 (UTC)

Real and ideal inductors
This section is a matter of focus - what departure from ideal needs assessed depends on the application. For radio frequency applications, stable inductance versus frequency (i.e. not get too close to self-resonance); for tuned circuits, it's Q (resistive elements); for filter applications, it's impedance rise/fall with frequency. So I think this level 2 section should be organized along these three topics. A circuit model (traditional 3-element to start) would be a great visual and circuit analysis aid. Sbalfour (talk) 23:31, 22 November 2017 (UTC)

The traditional 3-component model is only a start - it's ok at AC line frequencies, and even at SMPS frequencies, the errors are less than a few percent (usually). But at RF, the thing breaks down. And RF is common. What happens here is ugly - the resistive (dissipative) elements are 1) not in series with R (DCR) in the model, 2) they vary with frequency, and 3) they're non-linear. There's no standard circuit representation of a "frequency dependent resistor".  Whippersnappers write PhDs twiddling this model.  I found one paper that defined a 9-element model that it described as the "standard model". Yeow.  Do we want something like that here? Hw far do we go? Sbalfour (talk) 18:37, 23 November 2017 (UTC)

Ferromagnetic core inductor
The text says, For both of these processes [eddy currents and hysteresis], the energy loss per cycle of alternating current is constant, so core losses increase linearly with frequency. Bunk. I'm in audio electronics, and well know the non-linear characteristics of magcore inductors in speaker crossovers - I can actually hear them. Neither process is linear with frequency: eddy currents vary approx. as f^3/2 - f^2 while hysteresis losses vary approx. as f^1 - f^3/2. In practice, they just aren't separately measurable, so most authors lump them together according to the Steinmetz equation. Manufacturers' published data usually shows a frequency exponent between 1 and 1.4 or so for this equation. Further, there's an analytical derivation for "classical" eddy current variation with f2. This squared relationship is actually pretty well known; what's not so well known is the phenomenon of excess eddy currents: at higher frequencies, skin effects and nonlinear diffusion of magnetic flux from the skin to the interior of the core cause the frequency-dependency exponent to rise. In the RF range, that exponent is rather close to cubic. Sbalfour (talk) 20:38, 24 November 2017 (UTC)
 * Glad someone knows about this stuff. Maybe for this general article we should not include discussion of the exponent, and just say the losses "increase with frequency", leaving discussion of the rate of increase to the Core losses article? -- Chetvorno <i style="color:purple; font-size:smaller;">TALK</i> 05:19, 25 November 2017 (UTC)
 * I fixed & elaborated it in the same rather colloquial tone of the rest of the article. For exponents, see Steinmetz equation, which I also had to revamp. Sbalfour (talk) 16:59, 25 November 2017 (UTC)
 * The Core losses "article" is a redirect page that goes to Magnetic core (after I fixed it). That section is wimpy and unsourced. If we want a proper treatment, we're going to have to write it.  I'm inclined to stick any math into the Steinmetz's equation article. Sbalfour (talk) 18:45, 25 November 2017 (UTC)

This section is a miscellany of stuff, embodying three different considerations: application (choke), material (ferrite), and topology (toroid). It omits mention of amorphous (glass) cores, grain-orientated laminations, and nickel-iron soft cores like mumetal and permalloy. It needs a reorg as well as expansion along these lines. Sbalfour (talk) 03:44, 25 November 2017 (UTC)
 * I agree. What do you think about moving the "Choke" section out of the "Ferromagnetic core inductor" section and putting it under "Types of inductor"?  It isn't perfect, but I think the section should not be where it is. -- Chetvorno <i style="color:purple; font-size:smaller;">TALK</i> 06:53, 25 November 2017 (UTC)
 * Yeh, move it or I'll get around to moving it. It's a start. Sbalfour (talk) 16:59, 25 November 2017 (UTC)

Other related articles
There's


 * Inductor
 * Choke (electronics)
 * Gyrator
 * Magnetic inductance?? a mathematical theoretic aspect of gyrators
 * Electromagnetic induction (mostly about induction generators - no mention of induction motors)
 * Inductance
 * Leakage inductance (confined to transformers but has own article)
 * Mutual inductance (a redirect to Inductance)
 * Coupling (electronics) a lame article on a kind of meta-topic
 * Magnetic reactance, a truely opaque article on an abstract aspect of magnetic circuits ~"magnetic inductance"
 * Magnetic core
 * Ferrite core
 * (there are articles on mumetal, permalloy, etc in materials science perspective rather than magcore application)
 * Core loss (currently a redirect to Magnetic core)
 * Steinmetz's equation
 * Toroidal inductors and transformers
 * RL circuit (every real inductor has some R, so any circuit with an inductor)
 * Electromagnet

We have 15 lead articles here; I just don't think we have 15 distinct topics. I think the first consideration is, can a reader obtain facile and comprehensive access to the interrelated information on this topic? Sbalfour (talk) 05:53, 26 November 2017 (UTC)


 * Not to mention Magnetic circuit, Laminated core, Magnetic reactance, Magnetic impedance, Magnetic capacitance, and Inductive coupling. This proliferation of articles is pretty much par for the course on WP.  One improvement already in the works is that the confusing articles Magnetic impedance, Magnetic reactance, Magnetic effective resistance, Magnetic inductance and Magnetic capacitivity are going to be merged into Gyrator-capacitor model, because these obscure units are only used in this analogy between magnetic circuits and electric circuits. See Talk:Gyrator-capacitor model. -- Chetvorno <i style="color:purple; font-size:smaller;">TALK</i> 20:39, 26 November 2017 (UTC)


 * also Legg's equation. Glrx (talk) 21:58, 3 December 2017 (UTC)

Circuit analysis diff-EQ
Yo, user:chetvorno, the diff-EQ stuff at top of Circuit analysis looks a lot like the stuff you just did under Stored energy. In particular, the discharge equation at bottom is a direct descendant of the energy storage integral. The corresponding Capacitor section doesn't have this kind of math there. The calculus stuff is all one unit. You want to pick it up and merge it all together? Sbalfour (talk) 20:07, 23 November 2017 (UTC)

Fix this, if it fancies you: the differential relationship above shows... $$i(t) = I e^{-\frac{R}{L}t}$$ Actually, it does, but you certainly can't determine that by inspection. This is scholarly, but opaque (could've fooled me). Sbalfour (talk) 00:37, 24 November 2017 (UTC)


 * Re merging the "Stored energy" section into the "Circuit analysis" section: As you say both these sections use calculus, but so do other sections. My feeling is that the "Stored energy" stuff belongs where it is with the "Constitutive equation", "Lenz's law", and "Q factor" sections, because like them it is a property of the inductor alone, just dependent on the current through it, whereas the "Circuit analysis" section deals with behavior of circuits containing inductors with other components. -- Chetvorno <i style="color:purple; font-size:smaller;">TALK</i> 10:21, 4 December 2017 (UTC)


 * I agree the section with $$i(t) = I e^{-\frac{R}{L}t}$$, about a inductor-resistor circuit, is opaque and totally confusing. I'm wondering if we even need it in this article, since there is already an article RL circuit? -- Chetvorno <i style="color:purple; font-size:smaller;">TALK</i> 10:21, 4 December 2017 (UTC)

"Tank" circuit
The word "tank" is used (correctly) in the "Radio-frequency inductor" section (and in the nearby image caption). But it is not defined or glossed in this article. As a temporary measure I've linked it to LC circuit and also added that article to the "see also". But if anyone is curating here, please consider whether a reference to LC circuit belongs more prominently here. Shannock9 (talk) 22:00, 22 July 2018 (UTC)

Sorry I now see you have "tuned circuit" - which redirects to "LC circuit" - in the lead. Shannock9 (talk) 22:16, 22 July 2018 (UTC)

I question your table of "Inductance Formulas" for toroids and solenoids
It seems to me that Inductor is at best out of date, and possibly inaccurate. The formulas seem like they were written in the old days of ham radio and slide rules. The toroidal formulas should involve logarithms. Here are three better sources:
 * 1) https://cnx.org/contents/eg-XcBxE@8.86:9IPDyGBX@2/142-Self-Inductance-and-Induct
 * 2) http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/indtor.html
 * 3) http://www.phys.uri.edu/gerhard/PHY204/tsl267.pdf
 * --Guy vandegrift (talk) 14:45, 3 March 2018 (UTC)


 * Not to mention that the formulas for toroidal coils shown in the table are for air core, whereas the reader would be far more likely to encounter toroidal coils with a core of ferrite powder or other material, for which the formulas will include a relative mu value. Gwideman (talk) 02:41, 24 February 2020 (UTC)

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 * Transmitter tank inductor.jpg