9.1.2 Electric Dipole Radiation

[@rhdinah]

Thank you Jonathan for all the hard work you've done on presenting this material. I hope at some future time you'll be able to complete this series. It's been a help to a lot of people who are pursuing this difficult subject. Thanks again for all your hard work! It's been great! BTW I really like this fancy presentation, but handwritten notes are just fine with most of us I'm sure. Take care!

[@rontoolsie]

At 4:00, the law of cosines should allow the r+ to have the negative rsCos(theta) and the r- have the positive equivalent, which should invert the +/- sign under the radicals in lines 1,2 and 3....after the binomial approximation is made, the sign is however corrected to a (-/+) expression. And the diagram shows that r+ is shorter than r-, and therefore would have a subtractive term in it, while the latter would have an additive term. This error is carried over the 1/r+/- term. But apart from this, this video is extremely informative, if not a little busy!

[@maheshnerlekar9791]

understood in a very easy way ...because you took lot of hard pain to do it. thanks a lot

[@yamenarhim9336]

The new format is definitely better and more concise and to the point, it might lose some algebraic details but that's a price i am willing to take for clarity.

[@kakjsd]

If you can finish chapter 9, I would really appreciate it. Your videos have helped in stay in the class so far, but my final exam (in May) covers complete chapter 9 and 10. If you have time, please finish the chapter 9 at least.

[@yvieanna]

Thank you so much! I'm so happy you are back :)

[@jg394]

+Yvonne Hora I'm a lazy bum is what I am. I should get cracking on the next section. It's not hard, just tedious.

[@physicswithrauf-oe1on]

Good 👍

[@Visual_Music]

Thank you for adding details in the explanation! It will be awesome if more videos can be made in this series :)

[@physicslover9227]

Thank you so much Sir your videos are very useful :)... They explain concepts and ideas in a simple and clear way...Thank You so much Sir.... Thanking All, All Sincerely, Physics Lover

[@peterfreelion4987]

Thank you so much! I was looking for a (c/ω)/r to appear. It did cross me once that I could consider the whole sin(....)/r as zero safely but I thought I was not allowed because of the sin, so I rejected the idea. Your video saved me

[@jg394]

Thanks. I'm glad i can help.

[@XiaoHuWu]

You changed from using paper and pens to computer. Were you using a PC or a MAC?

[@emilioaguilera2212]

excelent work, i really aprecciate what you do. you've gained a new suscriber

[@bhobandreevelignig674]

what if we dont use the r>>s approximate and say r>s so that its just a bit longer?

[@jg394]

If you're that close to the dipoles, it behaves more like two charges. Far away, even though the two charges cancel and are only separated by a tiny distance, it has the surprising effect shown here.

[@ebz4125]

Thank you for posting these videos Jon! When is the next video?

[@jg394]

+Ebz So I tried my hand at the next one, and after several disheartening failures I've been thinking hard about where I need to go next. I'm pushing myself to finish this series but really, I want to teach calculus and basic physics to my son. So I'm having a hard time finding motivation to finish it.

[@briantheligman]

+jg394 haha no worries man. I really appreciated the videos you made! now guess tonight its just me and griffiths

[@ebz4125]

+Brian Heligman Good luck :)

[@mrnarason]

I hope see you comeback and finish the series even though I'm long done with the class!

[@pallabroy6414]

tensor representation is yet to be covered. It will be more exciting then.

[@aviadedell4826]

why were the signs changed during the binomial approximation?

[@DANGJOS]

Thank you for this. I mean you just blased through this complicated thing like it was nothing! One thing though. I didn't understand why you said "theta ^" points in the northern direction. Doesn't it always point tangential to the surface of the sphere, away from the north pole?

[@jg394]

In spherical coordinates, theta=0 is the equator, theta=pi is the north pole, and theta=-pi is the south pole. So for at any point on a sphere, the increasing theta will point north. Join me on Discord: discord.gg/TGK47Pf

[@riteshsingh2791]

This feels pretty much real physics

[@sathyrasmi741]

Your works and you are also amazing. This is helpful for people who is like me 😃😃... For this videos you are really working hard. Thank you very much. I appreciated your work and ideas. Again tnx. Oh you can make more videos based on physics. From bangladesh

[@jg394]

It is my intention to do so. I am recovering from the flu and a new job so eventually I'll get back to the videos.

[@sociofact1605]

Thank you sir your video help me to understand the dipole moment in very easy way

[@adambomb3513]

If I had an antenna dipole whose long= 1m and f=60Mhz, it is an infinitesimal or short dipole?

[@shobhitsharma5271]

Thank you sir for this video. This video really helped me a lot. But please don't mind sir because there are few mistakes in this. 1st is in the formula of curl of A, the first term of (theta) component, there should be A(phi) but you have taken A(theta). And I'm confused with the sign in the binomial expansion. Anyways sir you have done an excellent job by teaching this complicated derivation. Please make the video of lienert wiechert potential if possible. 😊

[@Fawadkhan-ju2eb]

Amazing Sir

[@charan018]

Perfect explanation 👌👌👌

[@naginashaheen1658]

Awesome video

[@merondemissie1199]

this was very helpful thank you very much and keep it up!

[@andycromwell8229]

This is problem 53.4 in the exercises for the Feynman lectures.

[@Salman.S33]

Why the equation q=q.coswt is used?

[@jonathangardner4842]

That's because the charge is oscillating between the two ends.

[@riteshsingh2791]

This really pretty much real physics

[@josephksajan1298]

Actually changing that R to r was too hard even i tried it even after applying approximations some terms still exists thats the real problem i didnt get that sine component alone

[@jg394]

I think I walk through all the approximations in this video. Is there a particular step that was confusing? Give me a time mark I'll look at it.

[@josephksajan1298]

@@jg394 ok☺️

[@enestepe]

Is paper better than white screen or am I getting old

[@jg394]

I like paper. It's more interesting for me to watch than slide shows.

[@enestepe]

Real Physics I agree with you. Please go on using papers if you make new videos.

[@jacobvandijk6525]

I think you did a nice job. But hurry a little less (in your life)! When your train has just gone, remember that there will be a next one ;-)

[@jg394]

Thanks! I think I've already asked you a few times, but join me on Discord: discord.gg/TGK47Pf

[@hershyfishman2929]

16:26 Your formula for del x A is wrong. The first term in red should be ∂Ar/∂φ instead of ∂Ar/∂θ, so it's not relevant to us as we have no φ dependence.

[@man-kmweene7827]

Very instrumental

[@ajayjamesthomas7154]

Thank you

[@ammarpotter]

You sound like John Krasinski.