Physics 46 Maxwell's Equations (7 of 30) Ampere's Law (Part 2)

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In this video I will explain Ampere's Law (Part 2).

[@discipulusoperarios2721]

This is an excellent lecture! Just in case of anyone went through unit check, actually, ∫Bds is a unit of B field, magnetic flux density with Webber/m, a density on an enclosed line, not the usual Tesla, webber/m^2, magnetic flux per area. So, do not be surprised to see the unit of Newton/Ampere, where just force acting over a current, because it is the same as Webber/m.

[@MichelvanBiezen]

Good input.

[@valeriereid2337]

It was difficult to understand displacement current from just reading the textbook. Thank you so much for making this easy to understand.

[@MichelvanBiezen]

You are welocme. Glad this made sense to you. 🙂

[@81546mot]

You do a really great job of explaining this--superb--I will watch all of your videos--they are superb. The only thing that could be improved is the blurriness of your video--it is very difficult to see--the 1080P defaults to 240P and you white board comes across a dull grey making it even more difficult to see. But your presentation is EXCELLENT

[@MichelvanBiezen]

+81546mot Yes, you are correct. This video is blurry even at high definition. We have improved the clarity over time, but these older videos could be better.

[@francoisegiraldo5038]

All your videos helped my pass Physics, and now I'm back 3 years later because I'm reviewing for the FE. Thank you for all your help! you're the best!

[@MichelvanBiezen]

Glad to help!

[@IronCharioteer]

I really like this vid series for review. I did all this material last semester but forgot a lot of the meaning over the break. Now i'm in E&M II and we're really going deep into Maxwell's eqns so i need a review. The 1st time i learned this our class followed Introduction to Electrodynamics (Griffiths, 2nd ed.) and so we learned everything bit by bit. But these vids combine material from the beginning of the semester with material from later in the semester and ties it all together. That is EXTREMELY helpful for review purposes. Thanks Michel!

[@zuhairalsaffar7001]

Sir your explanation for the 4th Maxwell s equation was more than excellent you have been like a river to a thirsty students thank you so much

[@huzaimkhan9269]

Amazing ...brilliant and superb..you have clear my all confusions about this concept...

[@leoclarkin5944]

Hi Michel, very much thanks, now I finally understand a "displacement current"; excellent explanation !!!!!!

[@MichelvanBiezen]

Great! Thank you for the comment.

[@poiuwnwang7109]

This is really cool! It's not been clear to me for years, now very clear. Thanks!!!

[@MichelvanBiezen]

Glad it was helpful!

[@dalisabe62]

Great job. You are good at explaining the formulas and relating them to the concept. You should though use a better whiteboard where the calculations could be more readable and hence easier to follow. However your verbal presentation is superb and it makes up for the whiteboard blur.

[@grizzers21]

saved my grade - thank you so much!

[@ssvaph]

So this equation tells us that Magnetic field can be created by the flow of current OR by the change of Electric flux. Did I get it correctly.

[@MichelvanBiezen]

That is correct.

[@ssvaph]

Thank you. Your video really help me a lot ;)

[@curtpiazza1688]

Great explanation!!

[@MichelvanBiezen]

Glad you liked it. 🙂

[@johannstettler9434]

Great lecture as usual! I just have a little question, wouldn’t the answer at the end be negative? Since the electricfield flux is decreasing, wouldn’t the change in flux be negative, giving us a negative value at the end?

[@MichelvanBiezen]

The difference between increasing and decreasing flux is the direction of the induced current and voltage.

[@ketankarkare6180]

Hi Michel, so it means that the line integral of the magnetic field with the area is equal to the sum of the rate of change on electric flux and the current enclosed, right?. So it depends on both or either of one??

[@BentHestad]

A tad difficult concept very well explained!

[@CatsBirds2010]

Well explained

[@zakirhussain-js9ku]

We know there is no displacement current as no charges are moving b/w capacitor plates. But we know when charges start building up on plates electric flux starts appearing b/w the plates. Increasing charges on plates increase & move electric flux. On full charging of capacitor flux becomes static. Magnetic flux appears only during motion of electric flux during charging & discharging of capacitor. Why we can't consider motion of electric flux in conductor as well as in capacitor. In such case in maxwell's 4th equation only flux will be involved.

[@MichelvanBiezen]

There is no ACTUAL displacement current, but that is the definition of it. If there was a current it would be equal to the displacement current, and it "completes" the circuit without actually making a connection.

[@zakirhussain-js9ku]

@@MichelvanBiezen I think electric & magnetic flux are each other's counterparts. Motion of one induces the other which takes current out of the equation. Magnetic field due to moving charges is valid only for conductor while moving flux is valid both for conductor(moving flux surrounding electrons) as well as capacitor.

[@yonkomera7467]

I have a question: when we consider the imaginary circle between the capacitor and, for example, the radius of that circle is greater than the radius of the capacitor, does that changes the magnetic field intensity or is it the same? Thank you for your lectures.

[@oneinabillion654]

That circle loop is amperes law, it has nothing to do with capacitor. It is the circular region whereby B is constant. So if u take different circles u would have different B. The bigger the circle, the further away it is from the current, and so the smaller the intensity.

[@kindjupiter]

thank you thank you thank you

[@x9z6x]

That was awesome man. Thank you.

[@ivanpanska2409]

thank you so much

[@oneinabillion654]

How eerie...

[@nielsmadsen2185]

Excellent

[@andrewjustin256]

Mr. Michael, if those terms turn out to be equivalent, then I can perform the following algebraic manipulation: |B• ds= 2u.I In other words, the like terms can be added, so two times one of the term. However, it does not feel right. Any words on that?

[@MichelvanBiezen]

The two terms represent a different quantity and are not expected to be equal to one another.

[@andrewjustin256]

@@MichelvanBiezen Very well! Thank you Mr. Michel.

[@Hc-in8gp]

Isn't his face really similar to mathematician Euler? XD. Thanks for these wonderful videos, Sir.

[@akashsunil7464]

It actually is the Younger version tho

[@zakirhussain-js9ku]

I think moving electric flux induces moving magnetic flux &vice versa.

[@MichelvanBiezen]

Not sure we can make that statement. We know the source of magnetic fields (moving charges) and we know the source of electric fields (presence of charge). A moving charge will generate a magnetic field and will cause the electric field to move with the charge.

[@zakirhussain-js9ku]

@@MichelvanBiezenSir you are correct & my statement could be wrong. I made this statement since 1) Direct current induces magnetic field w/o changing electric field. 2) Magnetic field is induced w/o any charge moving b/w capacitor plates. 3) Magnetic field of direct current or stationary magnet does not induce electric field since it is static. Electrons & protons are not pure electric charges. They also contain mass & magnetic charge. Mass has no role in EM induction. Therefore I am differentiating b/w electric charge & its electric field. It is true that electric charge produces electric field & moving charge induces magnetic field, but I think it is not electric charge but its moving electric field which induces magnetic field. I think in a conductor the moving electric field moves the electric field of electron & electron moves with its electric field.

[@ptyptypty3]

I notice that we tend to see the use of a Wire LOOP with the B-field passing ONLY through the INSIDE of the loop.. that allows for a current direction that establishes an opposing Magnetic Field. That means that the Field lines of the Current produced B-field is in the Opposite direction of the Changing Magnetic field Inside the Loop. but if the B- field is spread all over the loop, both inside and outside, can the Current flow in the loop create an Opposing Magnetic field? it would seem that the Circular B field around the conductor would Both Oppose AND reinforce the Magnetic Field surrounding the Looped wire. In other words..would the current be ZERO if both the INSIDE of the Loop and the OUTSIDE of the Loop were both subject to the same Changing B-field..?? Just had to ask.. (I see now why the more you learn... the more questions you have.)

[@MichelvanBiezen]

+Philip Y The B field outside the loop has no influence on the the induced voltage or the induced current.

[@nidhishgautam9043]

+Michel van Biezen exactly sir!

[@berfinceri2379]

Hi. I don't understand when to use displacement current. In some questions in my notes only displacement current is used to find the B field, and in some questions both displacement and current in the wire is used. Can someone explain it to me?

[@MichelvanBiezen]

Keep in mind that displacement currents are not real, but they represent what goes on between capacitor plates when the charges are entering or leaving the plates.

[@georgealexandris6341]

If μ•ε•(dΦ/dt) is equal to μ•I then shouldn't the equation be written as 2μ•ε•(dΦ/dt) or 2μ•l . Surely I have mixed something up so if you can enlighten me sir.

[@nikhilwardrobe]

when he said they are equal he is talking in term of units not the actual physical quantity, though they both are same in a way but way different from their origins.

[@rajcodes100]

Nice

[@MichelvanBiezen]

Thanks

[@timetraveller1237]

so is the second part of ampere law only applicable to capacitors if no where else is it applicable

[@MichelvanBiezen]

It doesn't have to be a capacitor. We just used a capacitor here to illustrate the principle, but there are other physical situations where this can be shown. (Capacitors just make it easier).

[@timetraveller1237]

ok thanks

[@TheBigBangggggg]

It looks all very blurry, Michel.

[@kirangudigar5394]

Current should be -ve, as it's ( 0c - 8.85 x 10^-9). Pls enlighten me

[@sandeshparajuli577]

Cant we see these two parts at once? I mean dont they coexist?

[@MichelvanBiezen]

The current (from the second term on the right side) is real and can be measured and it produces a magnetic field. The first term on the right side induces a magnetic field caused by the changing electric field (or flux), which acts as if there is a current. (you can think of that part as the "virtual" current or induced current).

[@TheBigBangggggg]

I would have described the concept first (difficult enough) and then put in the numbers. It feels a bit erratic.

[@mivapusa]

You are shaming my professors :)

[@mhdmouazawad8464]

thinks

[@uv-cat]

video is slightly blurry even in HD :/

[@MichelvanBiezen]

Yes, when we first starting to make these videos we had to learn a lot about focusing being affected by lighting conditions. We have since worked out the bugs.

[@av6966]

It's very much usable and Thank You! Michel

[@TheBigBangggggg]

DISPLACEMENT CURRENT is NOT a current (very unfortunate term)! It is called a current because it has the same effect as a real (conduction) current; the effect being the formation of an magnetic field. That's all ;-)

[@MichelvanBiezen]

You are correct in that it is not an actual current. The term DISPLACEMENT CURRENT has been used for over 100 years by millions of physicists.

[@TheBigBangggggg]

For an Exact Science a pretty weird situation: giving phenomena the wrong name! Of course it's the same with the concept of electric current. We all seem to know by now that electrons do the work. But the Physics society seems to like ambiguity and keeps talking of a conventional and a real current. Just bull...t! Why do physicists like to confuse people? Is it some global personality disorder? Or just laziness to do something about it?

[@TheBigBangggggg]

Your 100-years argument triggered me, Michel.

[@nocknock4832]

@@TheBigBangggggg go out there and make it your life mission to change the term!

[@xepho8205]

Well human languages have always been highly ambiguous, haven't they ... An "Exact Science" based on that will always be doomed to ambiguity, and vagueness, and contradiction ... En tout cas, wasn't the term "displacement current" due to Maxwell himself? I'm not sure, I seem to remember reading about it but google is failing me right now ... 😃👋

[@amsu7445]

thank you so much