3.2 Time Varying Fields

[@sharshabillian]

This came in very handy, thanks :-)

[@Nuctorn]

Clear explanation ty!

[@alwaysdisputin9930]

I've been trying for ages to work out why the electric field starts moving along the z direction i.e. why light moves away from the sheet mentioned in the video. All I know is that it's like ripples in a pond. No videos ever explain it. So many videos. So little proper explanation. :( However, I can see that this video is helpful! Now I have to study it carefully....maybe i'll be able to get my head around it if I just keep on thinking about it....

[@kingpetra6886]

The why is not in there or anywhere else. The direction of energy of an electromagnetic wave is at right angle to both electric field and the magnetic field of the wave. It is quantified in something called the Poynting vector named after the guy who discovered this. This has been confirmed by both observation and the mathematics behind all this theory in the 19th century. As to WHY it works this way you may have to be satisfied that with he following; the electromagnetic force is one of the four fundamental forces in the universe (the other being strong, weak and gravitational) and it is not unusual not to have a why to go along with the what. The criteria is that the math behind it predicts what will happen and the observations align with the math. EM theory is not easy to understand (having taken it in college) but this is a good video and with the kind of visual aids out there a lpt of this stuff is a lot more accessible to a lot more people than it used to be.

[@alwaysdisputin9930]

​@@kingpetra6886 We have electric field lines at the start & we know these field lines move outwards like a stone creates ripples on a pond. You're saying there is no reason why ripples move outwards. A wizard/Jedi/God did it with magic. Sorry NO I don't believe in your fairy tales. The stone pushes H₂O down - this is like the electric field at the start. The H₂O's connected by spring-like bonds. Neighbouring H₂O gets pulled down. So there must be something connecting neighbouring bits of space. Or else light doesn't move sideways.

[@kingpetra6886]

@@alwaysdisputin9930 No it is not like ripples in a pond. At first people assumed that there had to be a medium for light to move through because it was a wave and all waves seemed to need a medium to travel through ( like water in a pond.). ( It had been known light traveled in waves since the time of Newton). This medium was referred to as "ether". But during various attempts to measure the speed of light, the conclusion was drawn that there was no ether and there was no medium that light had to have in order to travel, i.e.e light could travel in a vacuum. You really are fucking ignorant but that is par for the course for a libtard. For EM waves, the key is the relation ship between the time varying electric field and the time varying magnetic field.which is presented after a fashion in this video.

[@alwaysdisputin9930]

@@kingpetra6886 When you use playground insults I just think you're morally defecating on yourself & find it funny. Ripples on a pond are like EM waves in MANY ways: amplitude, speed, wavelength, transverse, reflection, superposition, diffraction etc etc Empty vacuum is full of a sea of particles. A SEA. Therefore there is a medium

[@alwaysdisputin9930]

​@@kingpetra6886 anyway, u seem to have changed from "there's no reason why" to "the video explains it" E.g. let's say at t = 0 we have: rod ++++ a rod with + at 1 end / | | \ & - at the other | | | | which creates field lines | | | | \ | | / - - - - - We move all electrons to the other end of the rod & then in a later moment the space to the right now has electric field where before there was none rod - - - - - +++ / | | \ | | \ | | | | previous field lines - > | | | | | | | are moving to the right | | | \ | | / | | / +++++ - - - - How did the field lines move over there? Cause before you said there's no reason for why they moved over there but now you seem to think the video explains it?

[@rgudduu]

Direction of E field on the left side is wrongly shown. It should be same on both sides on plate. Check the curl of H field on the left side of plate...it is out of page (on top view), not into the page.

[@buckcostanza3483]

wow

[@yasserel-azab7033]

So, he spent years to come out with 4 equation which we have been handed in just half an hour hilarious :D

[@omega7377]

Pythagoras spend years to build a concept that a typical 4.th grader can easily grasp today :D Building concepts is A LOT harder than learning them.

[@chimponkoman]

You have an idea about how google works right? If google got deleted, do you think you could rebuild it? Now imagine if google never existed and you had to just come up with it from nowhere... Suddenly seems a lot harder huh?

[@kingpetra6886]

No, not hilarious, It's the difference between Western culture and non-Western culture, except for the time scale. With non-Western cultures it takes centuries to end up with nothing vs. years it takes in the West to come up with something that works.

[@alwaysdisputin9930]

@@kingpetra6886 i wish UK had trains that levitate in the air due to superconductivity like Japan & China. Perhaps this contradicts your theory a bit?

[@kingpetra6886]

@@alwaysdisputin9930 IThere are no superconductors at normal temperatures. The trains you are referring to are probably Maglev trains which use magnetic fields to levitate and propel the train. They work but are vary expensive to build. Overland routes of 200 to 300 hundred miles seem to be the typical applicayion. I don't know of any in use in subway systems like we have on the United States or in the UK for that matter. For short term term routes, these things can speed up and slow down fast enough enough that the G forces would bother a lot of people. A lot of people in the US criticize passenger trains of any type because they typical have to be heavily subsidized by the government to stay in operation. Keep wishing.