Recent content by alan123hk

It's hard to say how likely Voyager 1 is to be discovered by extraterrestrial intelligence. This is probably a very subjective guess. Moreover, it is conceivable that the probability of occurrence within 100 years should be extremely small, but the probability of occurrence within 1 million...

Precisely because the universe is so vast beyond our imagination, it is almost certain that in addition to the Earth, there are many other intelligent life forms in the universe, and it is only a matter of time before we discover them. If you want to know how big the universe is, I sincerely...

I am really interested in this topic, but obviously my ability in this area is not enough, so what I can do at this stage is to slowly learn and then understand. 🥲

I just want to describe that in the general transmission line model, it is usually assumed that due to the skin effect, the alternating current flows concentratedly through the conductor surface, and the electric field inside the conductor is approximately zero relative to the outside...

Maybe my English expression is not good. The electric field inside a conductor is zero, so of course energy cannot be transferred. I guess I should say that magnetic and electric fields guided by transmission lines transfer energy. In a coaxial line, these energies of course travel in the space...

I agree with your idea. This is how I understand it. The magnitude and direction of the magnetic field and induced electric field generated by the changing current are fixed in space. So how do the voltage and current output by the transformer, that is, the power flow based on the Poynting...

I just tried simplifing Jefimenko's equations https://en.wikipedia.org/wiki/Jefimenko%27s_equations based on quasi-static conditions and got some interesting results. Of course, Jefimenko's equations already provides a complete and accurate solution, and trying to simplify it seems pointless...

Sorry, I didn't read this https://www.physicsforums.com/threads/faradays-law-circular-loop-with-a-triangle.926206/page-6 in detail because I thought it was quite long and complicated. But allow me once again to offer some personal thoughts on this long-standing and much-criticized issue. I...

According to the definition of magnetic vector potential, $$ \mathbf {B} = ∇\times \mathbf{A}~~~~~~~~~~~~~~~~\mathbf{E}=-∇ \phi-\frac {\partial \mathbf{A}} {\partial t} ~~~(1) $$Since $$ ∇\times \mathbf{ E_i}=-\frac {\partial \mathbf{B}}{ \partial t } = -∇ \times \frac {\partial \mathbf{A}} {...

As far as I know, we can connect one of the two secondary outputs of the isolation transformer to ground and of course the output voltage will not change in this case. But this involves safety issues that need to be handled very carefully. The reason is that one of the main functions of...

Although if the earth is viewed as a conductive sphere, its capacitance is only 710uF, which seems pitifully small. But looking at it another way, considering the capacitance between the earth and the lower ionosphere, assuming an altitude of 50 kilometers, the capacitance between these...

Some further personal thoughts on "Ground". The definition of ground is generally considered to be that it can absorb or supply current without changing its potential, in other words, ground should be a perfect sink or source for current, so it is also an equipotential point or plane which...

There may be some communication issues here. For example, for a given circuit diagram, the values of all resistors, capacitors, resistors and their connection methods are determined and cannot be changed, so of course you can choose any point as a ground when analyzing the circuit diagram. But I...

I'm not very familiar with the the difference in customary interpretations of ground between physics and electrical engineering. But regardless, this is just a common reference point for us to communicate and deal with problems. If we don't use a common reference point, then every...

In order to reduce possible confusion and increase mutual understanding, I am wondering whether Faraday's law of induction can be expressed in the following form in practical applications. The magnetic flux of each loop from 1to n can be different. If the magnetic flux passing through the loop...