Ampere's Law: Magnetic Field in a Coaxial Cable

[@lNDlANSPlCE]

Why doesn't this have more views... I'm gonna share it with all my emag friends. Thank you, Ninja! When I graduate and have an engineer's salary I will be able to contribute and quantify my gratitude for your videos!

[@PhysicsNinja]

Thanks for the kind words!

[@dromero8127]

Hope you made it bud

[@johnstanford4610]

Beautifully explained - better than my book! Thanks

[@PhysicsNinja]

john stanford thanks!

[@ztac_dex]

*Cries in Jackson*

[@brianrook6207]

An outstanding presentation. It has cleared up all the problems I had understanding the physics behind coaxial cables. Thank you Brian Rook

[@ronnyalfons7096]

Without watching about 2 minutes of the video, i can already tell that there's good teaching in this video

Hey dude I guess you made a mistake. It will be good for you if you check the b

[@rifusaki]

You've just saved an anonymous student on the internet! This explanation is awesome!

[@libertyprime656]

Excellent video, thank you for creating this. Studying for my E&M final and this has been extremely helpful

[@laisguizelli25]

Congratulations from Brazil, your video help me a lot!!

[@PhysicsNinja]

Thanks for watching and the support. It's great to hear from students.

[@wlk1757]

I have question, in the b

[@leandrogarcia6396]

This is the best video on the god damn internet

[@piao-o3w]

It is the best video for a college student studying electromagnetism. It was very helpful. Thank you.

[@gideonkyeremeh868]

Thanks Ninja... Just got it at the right time for my presentation the next morning

[@etanetan101]

I think you just saved me before my midterm tomorrow. 😂 Thanks so much!!!

[@bobross5716]

Thank you so much! Not even Griffith’s could properly go over these types of problems

[@estebansingh9411]

In my experience KZbin tutorials work better than books. At least better than griffiths, purcell and thermodynamics books

[@dareadegun2460]

Thanks for the clear and smooth explanation

[@cosmolearner5562]

@21:05 Which current is taken positive and which one negative is also included in ampere's law - First arbitrarily consider the direction of path that you have choosen (generally taken same as magnetic field) The apply right hand thumb rule to the path choosen the direction of thumb is taken as positive that mean on applying RHT rule on path all the enclosed current in the direction of thumb are taken as positive and all other currents opposite to direction of thumb are taken as negative..

[@cnnn7885]

for b < r < c situation, why is it (r^2 - b^2) but not (r - b)^2 , same as (c^2 - b^2)

[@PhysicsNinja]

Because the area will be the difference between r and b. Pi- r^2 will be area. Of entire circle then take away area of inside part Pi-b^2. The area is not pi- ( r-b)^2

[@hughrountry1281]

Audio mixing could be improved, but the content is very helpful.

[@HakaiShakai]

Literally saved my life God bless your soul

[@jennykeeling747]

This was explained so well thank you so much!

[@lagado1lag]

Amazing! I really understood the exercise. Thank you!

[@kabandajamir9844]

The world's best teacher thanks sir

[@karthikkrishnan7558]

simple explanation...helped me a lot.. Thank you Sir

[@JH-ux1re]

Perfect! I was always confused by these things. Thank you very much! Saved me!

[@igorsantos-qj3zd]

Thx from Brazil!

[@rodolfogarcia6263]

Would a

[@PhysicsNinja]

This is done @ 10:44. In this case the field is not 0 because the Amperian loop will enclose all of the current within the small wire in the middle.

[@sanskararora6425]

as the inner cylinder is a conductor so all charges would be at the surface of the cylinder and hence the current should flow through the surface (as current is the flow of charges) so I would be zero for r

[@HuFocus-f2y]

Why cant my professors make videos like these!!! Thank you

[@shaunwu3609]

Thanks for going into the details! You have a nice voice as well!

[@Mehmetalp99]

Great explanation

[@PhysicsNinja]

Glad you think so!

[@Arif.mohmand]

Very nicely presented, at the end you said, it was a special coaxial cable with the both the same currents, thats is why B is zero, wasn't it zero because they were different currents in the direction?

[@PhysicsNinja]

Same current, different direction will result in 0 field outside of cable because total current enclosed is 0.

[@salmamahameed2160]

this isn't an empty cable right? like it's not a shell of a coaxial cylinder cable? and if that was the case shouldn't the magnetic field in the r

[@lilac.2858]

So well explained!

[@juliazhang3600]

simple explanation! I love it!

[@sor3na369]

Thanks for great explanation.

[@ShrabantiDeb]

better explanation than books..

[@brayschway6746]

This was beautifully done. Thank you.

[@asgoodasbread5559]

Great Explanation !! TY

[@maxdougherty3429]

Great explanation! I wish I had you teaching my physics class!

[@sealol5209]

Thanks man! Was having trouble understanding this question!

[@뿌엥-w7d]

You’re better than my professor, thank you

[@yusufkeskinoz9740]

Sound needs to be fixed but other than that lecture is okay

[@boysenbeary]

Great explanation!

[@user-ny1vt3ek4i]

Thank you Physics Ninja!!!!

[@uchennaubeh9498]

Thanks so much, this clarified my Delima about the magnetic field everywhere in space.

[@lukedimitriades9835]

Now your only dilemma is learning how to spell dilemma 😂

[@thuonghoang530]

thank for your lectures, I am a teacher, I would like to know exactly the divide you (everyone) used to draw lectures beautifully?

[@jorgemillan4041]

these are great please make more

[@masouddayaghi5923]

Thanks a lot man, it was wonderful.

[@hasranman]

This really helped me. Thanks!

[@rakibuddin385]

Thank you so much .you explained so easily

[@taladiv3415]

Thank you for this clear solution.

[@pierretobgui1792]

Really helpful

[@saffyt348]

This was so helpful! Thank you!

[@PhysicsNinja]

Glad the video was helpful for you.

[@aprilsianpi7973]

i don't think you have to include the interior of I at 13:20 minutes in region (b

[@PhysicsNinja]

Yes you do, it’s the total current enclosed by the loop.

[@PhysicsNinja]

Superposition of fields

[@aprilsianpi7973]

@@PhysicsNinja Thank you. You clear up all my confusion.

[@EnzoChai]

Tq very much man...save my day 🙌🙏

[@MayankLC93]

GREAT HELP SIR !!! 💞INDIA

[@linjisoo9975]

Very helpful video!

[@akibmostabe98]

Well explained,but when u do the closed integration it should be integration over rho product with dfi according to cylindrical co-ordinate system(Here rho is a product with dfi because rho is the perimeter across the arc dfi).Above all its good. Another thing is that u may use H(Magnetic field intensity) instead of B (Magnetic flux density) because when we r considering free space only then they aren't equal that is B=meu(o).H.But in practical cases medium may vary according to products choice

[@johnkay1952]

Just wondering, does this implication of the magnetic field being 0 outside the outer loop bypass the limitations of really small computers? I remember hearing somewhere that there's a limitation of how small circuit elements can get because their magnetic field would induce currents in nearby circuit elements.

[@TheLeontheking]

Good question! I'm not educated enough to answer it, but I would guess that for these small scales the classical theory presented here does not longer hold.

[@km-sc4kz]

is there any possibility of electric field being produced by this coaxial cable (atleast in a

[@ferhat_ee-76]

man you are the best, I tried to find the answer to the same question

[@yamaan93]

it's a good video and good explanation but the microphone popping makes it quite difficult to listen to

[@PhysicsNinja]

Thanks. Ninja has a new microphone now.

[@betulguncaldi4676]

Beautiful explanation! You're great! :)

[@allendeguzman6771]

wow. you nailed it,, well explained.. Wonder if you could make videos about magnetic moments for rotating charge disk, spheres, etc.

[@PhysicsNinja]

Thanks for the comment, i'll make a video tomorrow night comparing the magnetic moments of a disk, spherical shell, and a uniformly charged sphere. Physics Ninja loves requests!

[@allendeguzman6771]

cant wait to learn form that video.. ,,, this might be too much but it will makes sense if there is also a great video about electric fields, (gauss law) or gaussian surfaces to see connections to amperes law(amperian surfaces.

[@PhysicsNinja]

i have a few videos on Gauss' Law. Here's the first of the series. kzbin.info/www/bejne/nHilYpapoJynjpo I'll try to finish the one on magnetic moments soon. Physics Ninja is a busy guy!

[@PhysicsNinja]

Here's the first part of magnetic moment series. I'll add the other 2 parts tonight. Happy Learning! kzbin.info/www/bejne/aneToZKMq76pg8U

[@RicktokSV]

Hi ninja ninja leader. Cheers!!. I have a question, what is the difference between magnetic field and magnetic field intensity? Thank you.

[@peytonkliewer1997]

Thank you so much! This was very helpful!

[@aysenuratagun]

Thanks a lot, this video helps me a lot anytime i need :)

[@JD867]

You're awesome. This helped me a lot.

[@fatmanur5409]

Could you please also calculate the current density for each interval?

[@matthew_bang]

Fantastic work

[@yigitarsoy1944]

This is awesome!

[@teambananakinns]

what if the equation was asking for r

[@PhysicsNinja]

I think the solution cover all values of r. Maybe i don't understand your question

[@antiquarian1773]

what would happen if the currents aren't flowing in the opposite directions? would that mean the current is doubled when r is greater than c?

[@PhysicsNinja]

Yes you are correct, the field would be be different inside the outer shell and outside of both the field would that of a wire with current =2I

[@antiquarian1773]

@@PhysicsNinja thank you for the quick response!!

[@eckardbezuidenhout]

Hello sir, thank you for your thorough explanation. I just need to understand something please. Let us for now consider only the small conductor (gold). Seeing that it is a conductor, will all the charge/current not be located on it's surface only? Ergo, a proper Amperian loop would be such that it goes around the entire conductor and not inside the conductor. This would then change the outcome of this part and the rest of the problem. I need to understand this because there are so many people on the internet doing their own thing and in the end the information conflicts in the small but very necessary details. Thank you again for this explanation.

[@braceyourselvesfortruth2492]

Not 100% sure but you may be confusing current (moving charges) with static charges. Current is based on cross-sectional density so the amount of the wire we draw our loop around determines the total enclosed current.

[@RinaNewhouse]

Do you know why it matters to take the fraction of the AREA of the cylinders when finding the B field in situations 1 and 3?

[@PhysicsNinja]

Why ratio of areas?

[@kateystevenson7912]

Great video, thank you!

[@kholoudhakim7887]

thanks so much

[@asemshaat6672]

That video saved my life

[@antirunescape4128]

thanks but too many ads interrupting

[@limdronephooh910]

You choose the premium and no advertising

[@asmartguycodename4721]

Thanks for this great help. 😃

[@johngordon8513]

ur a legend

[@JamBergMann]

Great explanation! Thank you. Can we also calculate the B-Field for high frequency currents taking the skin effect into consideration with this method?

[@nabeelljassim6652]

Great good teacher

[@MaDcAmStErGaming]

Thanks physics ninja, you might help me not fail uni xxx

[@fatmanur5409]

Why do we ignore the outside thin hollow cylindrical conductor in which the current goes into the page?

[@PhysicsNinja]

Amperes law states that it’s only the current enclosed in the loop that will contribute. You only include the outer shell if you are calculating the field outside the coaxial cable.

[@martinsibanda8026]

thank you well explained

[@joepaschal6426]

How could you do this same problem butt starting from the magnetic energy density of a ideal solenoid and combining that with amperes law to find the density as a function of distance radial out from the axis and use this to find the inductance in the cable. thank you.

[@THEWouter1212]

Thanks a lot!

[@3washoka]

Thank you 🙏🏼

[@monoinluv4894]

13:23 does the direction of the current matter in terms of the sign for B? would dl and b be in the same direction?

[@ezefferth]

Brasil love's you!! grateful!!

[@ozanyldz445]

thanks a lot

[@alexkarampelas2200]

its supposed to be the integral of B dot dS, not B dot dl, since it's a surface integral instead of a line integral

[@PhysicsNinja]

No it’s not

[@abhishekpawarpoems]

Thanks brother!

[@helldi2blo]

thanks a ton!! i couldnt understand the solution given in my text, they didnt clearly write the exolanation.

[@killirina]

dude, thank you!

[@k12h6]

Thanks man

[@PhysicsNinja]

Happy to help!

[@xhelixshotx]

Very clear explanation, thank you! On a side note though, in the final screen you accidentally put another I in the equation for b < r < c

[@PhysicsNinja]

Marc thanks, looks like an extra I got in there from my cut and paste.

[@griffithfimeto3387]

Why there is current in outer conducter current oppsite to inner ? Please answer

[@elimiNator345]

Because coaxial cables work so that the magnetic flux density cancels and doesn’t interfere with its surroundings. To do that the currents must be opposite

[@syedmuhammadhaziqbinsyedah767]

Thank you :3