Inductors and Intro to Self-Inductance | Doc Physics

We discuss how to make an inductor and solve for the self-inductance of a simple solenoid.

[@MrRdoc94]

You are the patrckjmt of physics and that says alot, thanks so much for your videos.

[@cesareborgia9259]

Patrickjmt's videos are a shortcut to getting grades not actual intuitive explanations of mathematical concepts. Doc Schuster is way better.

[@Kyle_da_athlete]

@@cesareborgia9259 i agree but sometimes that is what is needed. For example, if you have an exam coming up in a short space of time, it allows you to get a passing grade. And then you can use more intuitive videos after to better understand the concept.

[@doubleblobs]

this is truth! love patrickjmt saved my calc 3 grade

[@Brooke-hy7ey]

I love how excited he is about physics!!

[@jacobvandijk6525]

His excitement does not always make it more clear. Sometimes a bit too much noise on the line.

[@SparkFastt]

For an Electrical Engineer brushing up on his basics, these videos are the best I have found online, hands down! Us engineers need to understand these things by intuition, and your videos are perfect for this. Don't stop making these! Question: Does a strait wire have the same inductance if you were to coil it up? Can you make a video going through why inductors should be coiled up rather than straight lines? Isn't there still the same amount of magnetic field regardless of the wire's geometry?

[@craigcoates6247]

you're crazy, and you make me look crazy when people in the library see me laughing my face off at a physics video. awesome stuff

[@DocSchuster]

+Craig Coates sorry?

[@ManyHeavens42]

sorry buddy

[@BannAlHassann]

I've been studying physics for years & I can say that nobody explains things like you do. Be my teacher please☹️☹️!!

[@rachaelchant5252]

Extremely helpful! My textbook defines inductance as a proportionality constant, but it makes much more sense to see it drawn and explained so well. Thank you

[@ShonKinsley]

This is the best explanation that i ever had.

[@christiangonzales1485]

at the 2:45 mark my brain finally started to understand inductors. You are super amazing at explaining concepts. Back in college, I just memorized a lot of concepts, but now I can finally understand them and know the real physics behind them.

[@ashfernandes7327]

You sir, are the very definition of a good physics teacher.

[@engmac18]

THE BEGINNING OMG HAHAHAHAHAHHAA X) Oh man, you're amazing

[@engmac18]

#savingmygrade

[@savvyfavy5805]

Thank you so much for this video. I could not understand inductors for the life of me and this was absolutely entertaining and informational. I love that you put personalities into your devices. I learn the best that way.

[@heterosapien69]

+Faviolanny Rath Yea it is entertaining..but you can't tell your instructor that the coil "got used" to the current when he asks why the opposing voltage of the coil diminishes over time.

[@adamblake1810]

you sir are a fantastic teacher! great enthusiasm and humor, you make physics fun!

[@sophiaqi7020]

love your explanations ! it helps me a lot always. my professor always rush and never explains too much, we have to study a lot after class to get the points clear.

[@sFeral]

that's a really nice formula u got there at the end, especially the "n" since the "N" and "l" scale proportionally if the wire length is fixed (implying a wire diameter) N=1/l=the diameter = constant aka fixed

[@JubelMaria]

You are an amazing teacher! After years of dreading Physics, thanks for making me enjoy it!

[@lavanyajoneja1172]

This is just awesome ! Three cheers for doc schuster :)

[@bartalor]

best explanation I could find about inductors, thanks so much!

[@SparkFastt]

Doc, Thanks for pointing me in the right direction! I spent the better part of 15 hours or so over this last week trying to find an answer to this question and essentially re-learning most of my schooling in this topic. I now have an answer that I am satisfied with (which is too long for a reply -- maybe I should make a video response), the consequence of which seems to state that "there is no (self)inductance outside of a straight wire. It is not defined."

[@jimmybuu3179]

Thanks Doc. Great instruction.

[@osamaalsaad3036]

hahahahaha " Henry, Named after a good student that i had a few years ago"" thats what i like about your videos .. you're making physics fun

[@arilee5450]

Thank you. It is extremely helpful!

[@patrickrosborough7634]

Man I wish I had you as my Physics Prof. You rock Doc! 😉👍🏻

[@chaudry123]

I really love the equivalent ckt diagrams drawn at the right instants.

[@franciscoabusleme9085]

Congratulations, very insightfull

[@kshitijsharma3170]

Quality content

[@vishnukaushal8396]

The Very Best! Man I'ma big fan

[@Nswoqhqoqb]

This guy is so informative and funny haha Thank you for useful video!

[@GottaLoveTheSound]

You are awesome!!! Your a great teacher

[@MobileLinkr]

Thank you from Korea, too.

[@saranyaram29]

oh god,tis guy makes physics super easy and fun!!!! love it

[@heterosapien69]

lol 1:31 "and this is a switch here, aint no thanggg, and..."

[@nkirukaa.486]

Your videos are amazing! Extremely helpful

[@DocSchuster]

Thanks, pal!

[@DamnTheDude]

what an enthusiasm!!

[@sarazinbi1530]

awesome Thank you so much

[@mopar3502001]

Definitely a great video! I'm subscribing to your channel immediately!

[@DocSchuster]

Welcome, friend!

[@bisisamosa2818]

Sooper!

[@aidleopard7716]

very dramatic :D Loved it

[@BloomwinxSuper1]

Years later... THANK YOU.

[@mohamadjanoun9869]

Excellent

[@roykay2224]

the way that you explainn👏👏👏

[@DocSchuster]

Boy, that's a great question. So, my initial thought is this: B curls around the wire, so if the wire is perfectly straight, the field from one section of wire CANNOT react with any other section of the wire. As soon as you curve the wire even a bit, you get the wire's field affecting the same wire's current at another point. That's the essence of self-inductance. I'm more naturally inclined to think in terms of loops or fractions and multiples thereof, but the bending is really the cause!

[@uceee1]

Yeah, because the field is not at the normal direction anymore and has to be decompose into all 3 directions.

[@rapsrule23]

Sir, you are a goon. Thank-you

[@mollypete4270]

I love the personification of the inductor.

[@rosim8470]

Question: is the induced EMF voltage the same as the voltage on the battery terminals??

[@waikiki.]

does the electricity still flow from the "bad battery"? From positive through positive, then negative to negative??

[@MysticMD]

Thank you my love

[@JohnnyKnight5talker]

tried to integrate elf at 2:50 XD

[@tramaynethomas3960]

You. Are. AWESOME! Is this a sub? You bet your pants it is!

[@DocSchuster]

Tramayne Thomas I'll get more pants!

[@sbader119]

why did you convert N/l=n? and what will the unit be of n?

[@russellokamura2022]

Can you explain Constant Phase Elements (CPE's) They are common in Electrochemical Impedance Spectroscopy which is used in academia for gaining insight on electrochmical reactions occurring at an interface

[@eljardinero8752]

Can the equation at the bottom of the paper at the end of your video be used to calculate the number of turns for any cylindrical coil or does the length of the coil have to be at least 10 times the diameter?

[@DocSchuster]

El Jardinero I guess we are making some assumptions here. I am ignoring edge effects, and it seems like your guideline is reasonable. Of course, the maximum error you can tolerate should determine how carefully you investigate the specific peculiarities of your setup.

[@chaudry123]

The mechanical analogue of inductance is inertia i.e Newton first law of motion.

[@willylagwinski9749]

How about explaining it all in terms of energy. Inductance being a property of space relating electric current to magnetic field energy.

[@benibena1738]

you amazing

[@last9827]

What is the little arrow above I (drawn at 2:04) and B ("field" drawn at 2:22) indicating? I'm not even sure it is supposed to be an arrow, it could be an angle. I've seen it on numerous KZbin videos (possibly only American videos).

[@DocSchuster]

That's how I signify that a variable is a vector.

[@biruktawityaze9773]

I was 7 when this video was released and look at me now 9 years later

[@Daski69]

what is it specifically that induces the voltage/"generates" the current going the opposite way? There must be forces in opposite directions i would assume but with the right hand rule at least I can't see it making any sense. help highly appreciated ^^

[@DocSchuster]

Daski69 Yeah, super question. Ultimately, you can break it down to the RHR, but it's very convoluted at the point of self-inductance. See if you can use RHR to derive Lenz's Law for a simple square loop leaving a uniform B. If so, perhaps you'll be comfortable using Lenz's Law to show self-inductance.

[@Daski69]

Doc Schuster thanks for the answer! I try to visualize a square loop and approaching its center with the negative pole of a magnet, using RHR, I think about current going into the page and the field lines going left, that would make the force go up, not out of the page.

[@diveruzumaki5556]

I love you as much as I love BTS ❤ U are a saviour ❤

[@uceee1]

Is that suppose to be a miu0 x miur ?

[@isaamthalhath4359]

They are badasses

[@j0mezzy]

Wait, will it still act as a "bad battery" if the coils were wrapped the other way ?

[@DocSchuster]

YES!!!!!!!!!!!!!!!!!!!!

[@prateekgurjar1651]

Jomel Sagsagat lol

[@brianalee6591]

What is the purpose of having a resistor in a circuit with a solenoid (RL circuit)?

[@DocSchuster]

+Briana Lee Great question! I suppose it's just a frank assessment of the utter impossibility of infinite current. But put a C in that circuit as well, and additional resistance broadens the resonance curve. Punk rock!

[@patriciabarros4630]

What does mu not stand for? Thanks for your videos, they're very helpful! :)

[@DocSchuster]

Patricia Barros It's a constant of the universe called the permeability of free space.

[@patriciabarros4630]

thanks !

[@bowenxu2882]

8:09 Is that a 2? Z? I? Sir you redefined the calligraphy of L

[@mcboomsauce7922]

“Bad battery” thanks I’m pretty terrible at the math, but I’m not really trying to be an engineer, I just kind of want a tentative grasp on what’s going on I’ve watched 3 hours of videos that try to describe something as a bunch of fractions, and frankly I’m too stupid and too lazy to put in the mental effort, But, the good news is, I don’t make space ships for a living And, from how I learn...you gotta see a chair before someone starts trying to tell you what sitting in a chair is like....rather than saying “a chair is a great way for a biped to reduce their potential energy by a factor of 1/2 Describing the abstract with more abstract is not one of my strong suits

[@tedsheridan8725]

How does "N squared" become "N skwer" ?

[@stevenlee1726]

two question: 1.when switch is closed, why the voltage across solenoid immediately equal to the voltage supplied.2.switch is close , is there any current flow in the circuit?? my assumption: 1. current flow through solenoid. the changes of current is maximum due to initially no back emf. this causes the voltage maximum. but if there is current flow in circuit, then why the voltage across resistor will be zero. urgent!!

[@sweetradish4857]

What is lowercase n stand for??

[@DocSchuster]

+Aina Mary N/L

[@hili467]

if you start with mo,*[N^2/L)*A and substitute in n = N/L, then N^2/L would become n*N, so it would be mo,*n*N*A. Not sure which parts of your beginning and ending equations are right or wrong, but the last substitution step doesn't work for me.

[@mprub4]

"n squor"

[@audreyandremington5265]

N skwere

[@jeremiroivas1628]

I too think that you forgot to tell things in this video. If you try to teach how inductor works, you might want to tell that it can fight change in voltage and current thus smoothing dc may obtained. To thing about DC simple coil is like wire but change in AC it don't like and tries to fight back. Thus smoothing some noise in DC path is good use for the Coil.

[@DocSchuster]

Thanks! Did you watch the next inductor video? I can't tell you all about inductors in 12 minutes, of course! That's a neat application, though.

[@AhmadTalkss]

What does induced mean?

[@2013Aleksey2013]

I'm still struggling to grasp the concept of inductance :) so it's the ability of a coil to resist any change in current through it whether it's increasing or decreasing current (that determines the polarity of self-induced voltage - if current through an inductor increases the voltage of self-inductance will orient itself such as to oppose the source of change - if it's decreasing then the voltage of self-inductance will have such a polarity as to compensate the source of change). L = e/(di/dt) suggests that an inductor with high inductance value will be able to generate more voltage of self-inductance and allow less current change per unit time (transient response of an inductor to a sudden change in its magnetic field) than that with a low inductance. In other words even if the rate of change of current is small the coil with high value of inductance will still produce a voltage of appreciable magnitude.

[@DocSchuster]

2013Aleksey2013 All seems great except "and allow less current through it per unit time than that with a low inductance." Current CHANGE per unit time. Magnitude of current is not considered at all in this case (but prolly should be before you build a circuit...)

[@2013Aleksey2013]

Doc Schuster I get lost every time the derivatives are present in an equation (the whole calculus thing). You've pointed out exactly to what I didn't quite understand. Have watched several of your videos in a row I have no idea how you manage to address such difficult topics and yet do not resort to complex math of dynamic systems.

[@DocSchuster]

2013Aleksey2013 It's a fine line to walk, right? I remember always struggling with the math, so I try to keep my intro-level videos heavy on concepts and (hopefully) building understanding. Thanks for watching.

[@graphene1487]

6:37 induuuuuuUUUUUUUced :)

[@jyothirmayababughanta9347]

What does it mean dat the bad battery dies eventually??

[@DocSchuster]

+sai gautham As resistance takes away the opposing current in the inductor, the bad battery gradually ceases to exist.

[@wedmunds]

What happens if you connect an inductor to AC?

[@prateekgurjar1651]

Wolf Edmunds then the bad battery gets reincarnated in every period and dies in every period

[@wedmunds]

Lol you could have just said that it would offset the voltage oscillations so that it leads current by pi/2...

[@ManyHeavens42]

the human body is the same way.electrons should flow through the body I'm going to fix that ,? Reverse the field,on the outside,from the inside,

[@GlitteryMunchkinxo]

i thought current flowed from negative to positive?

[@DocSchuster]

+Starlight 567 Your teacher may be using electron current. Current is defined as the motion of positive charge carriers.

[@Mech.Masters]

But current should flow from negative to positive,because current is a flow of electrons... Why did u choose the other direction please help? Why direction of current is opposite to that of an electron?

[@janrozenstruik]

This is because the classical current is from positive to negative. Back in the day when they didn't know whether the negative or positive particles flowed, they chose poorly by picking current as a flow of positive particles. As a result we still treat circuits as if the positive particles are flowing. Of course for some cases looking at the particle that's really flowing makes a lot of things more clear, but generally you will still find that the classical concept of current is being used in science.

[@pwilson001]

Ditto Jan, The early electrical scientists decided that current would flow from positive to negative, called conventional current flow. Had they known what we know now about electron flow, it would have been the other way. US use electron flow whereas UK and Australia use conventional flow. Whichever way you depict current flow usually depends on how it is taught in your educational system- conventional flow vs electron flow.

[@funcionamaldito]

I think simple stating that "the inductor does not want a change in current" misses the opportunity to relate the changing magnetic field to the producing of the emf in the coil. Could have mentioned that the coil experiences a change in magnetic field from the changing current in the turns of the coil, which makes the coil originate an opposing emf. The formulas gave a hint but you did not offer an explanation. It helps to enforce the innate relationship between electricity and magnetism a little more. I think it's natural for people to wonder, well, we have all this changing current producing a magnetic field around the coil, how about how this magnetic field interacts with the coil it comes in contact?

[@DocSchuster]

Sara Darella Good reasoning, Sara! I believe I have addressed this in the preceding videos. Maybe you jumped in during the middle of my "series"? Lenz's Law is my very favorite physical law!

[@Daski69]

Sara Darella Then please, answer me this; what is it exactly that induces an opposite emf? I assumed there had to be a force since it's changing the way that electrons flow but how does the magnetic field do it? It intervenes with other field lines and so what? most grateful for answer, exam coming up =)

[@KiratAlreja]

I am going to give my physics final now and I'll come back and edit this comment about how it went Edit : it went fine . Lol

[@nabeeltech7885]

Out of the way newton hahahah

[@bazzalseed]

Newton Away!

[@devinmccloud]

“Today's scientists have substituted mathematics for experiments, and they wander off through equation after equation, and eventually build a structure which has no relation to reality. ”

[@MrKellyclarksen]

you bet your pants it does!

[@DocSchuster]

Emilys Flaws MORE PANTS!

[@MikeyGunit24]

Squurrr

[@nathansd8]

"you bet your pants"

[@EstebanGarcia-ph5gt]

inductors are biopolar hahahahaha

[@shantakumari1503]

bad battery=insulator

[@esfasia9835]

Come on man, wth you are telling. Inductor isn't acting as a battery neither creating any voltage. The electricity just having hard time to move through the curved winding therefore requiring more pressure (volt). That's it. The condition feels like inductor is generating voltage but that is not the reality. Inductance is more like absorption of current flow not prevention. info like that makes confusion, don't do that.

[@wedmunds]

Good battery bad battery

[@samanthamar949]

sqwure

[@Tonytone992000]

He's a weirdo but he's smart.lol

[@guest3858]

has the logic of a chick

[@SkrollrBeats]

why do u draw your L so fancy?

[@martinmartinmartin2996]

"wants" like a living creature ! "fickle nature" like a creature with emotions! "Dying, Bad battery " as if it were alive... and it is "Bad" OK these terms are perfect for a cartoon, but not so much for understanding the complicated concept of inductance.

[@cityzen8539]

thats why i dont like physician. they always facing reality to other direction