My confusion started because of the following lines in a text book i am reading (skilling - fundamentals of electric waves) where there is quote along the lines ofWhere is the similarity between those two, apart from the common frequency?
The special case is mainly non-radiation of EM energy in free-space, the energy from point A to point B remains in the near-field and it's field components can be computed accurately using point measured voltage/current magnitudes and phases. It's mainly a matter of circuit size and signal wavelength that determines when "circuit theory" stops being accurate not a absolute frequency.My confusion started because of the following lines in a text book i am reading (skilling - fundamentals of electric waves) where there is quote along the lines of
"circuit theory may be considered as a special case of more general theory of electromagnetic fields" from page numbered 1.
You will be confused if you think that "electricity" is different from EM energy.@mfb and @nsaspook : thanks for the reply.
Quoting from http://www.capturedlightning.com/frames/Non-Herzian_Waves.html
"but one particularly useful consequence is the tendency of long thin conductors to guide an EM wave along themselves. When an EM field is guided in this way, we call it electricity flowing along a wire,"
It is from the section titled "How do charges behave in a conductor?"
This confuses me even more.
Tesla would be entitled, as any electrician is, to say that the energy is carried by the current. But he fails to appreciate that the current will only flow in conjunction with the associated field. The current will not flow without the field, because by definition the field is that thing which applies a force to a particle through the particle's property of charge. Short of proposing a fundamental new interaction involving charge (which he doesn't seem to be doing) Tesla's proposals can only be based on a fairly elementary failure to appreciate just what charges, currents and fields are all about.
This is, indeed, a rather common misconception, and often occurs amongst those trained in electronics and electrical engineering. It is natural (and perfectly reasonable within those domains) to think of the energy as flowing through wires, carried by currents. Voltage is seen as a kind of pressure and current is regarded as a flow of 'electricity', much like a flow of water in a pipe. Fields are regarded as incidental, sometimes a nuisance, and electricians are happy enough with any circuit until the wires reach an antenna, at which point a mysterious thing called radiation happens. The electrician's explanations tend to disolve into handwaving at that point as he struggles to address the question of just where and how is the energy transferred from the circuit to the field.
The physicist sees things differently by viewing nature from a wider perspective - one which isn't constrained by the limited and artificial view of nature given by circuit theory. When looking at an electrical circuit, the physicist sees a complex pattern of E and H fields formed into a rich and marvelously functional 3-D pattern by the boundary conditions imposed by lots of carefully arranged conductors and dielectrics. The technology of arranging those conductors and dielectrics is called electronics. Here and there those conductors might be formed into shapes that allow the fields to spread out in certain useful ways, and the electrician would call one of those bits the antenna.
The physicist's view of an electronic circuit as an intricate pattern of ripples and tensions in the EM field, anchored in place by a beautifully crafted assemblage of materials, is a wonder to behold and helps us to remember that no change in the physics occurs when we move from 'energy in the circuit' to 'energy in the air', and that such a move is merely a convenient change of descriptive language.
By the way, note that it is not necessary for us to say that the current 'causes' the field, or that the field 'causes' the current. There's no cause and effect process in EM interactions at the fundamental level. EM doesn't contain an 'arrow of time'. It is only when thermodynamics steps in, and you start to look at the so called entropy of the system that it becomes meaningful to say that energy flows from A to B. As far as the particle/field is concerned it is just A interacting with B. It is only when you move outside EM and consider the thermodynamic implications of the A-B interaction that you can begin to identify a cause-effect relationship. Only then can you unambiguously declare one to be the 'source' and the other to be the 'load'. The important thing is that charge and field are inseparable, you can't choose between one or the other as a choice of energy transfer mechanism, but you can choose between them as descriptions of the transfer process, and of course, both give the same correct answers.
Where is the similarity between those two, apart from the common frequency?
Sorry for bringing it up again, but could you please clear this confusionYou will be confused if you think that "electricity" is different from EM energy.
From your link:
My standard "what is electricity" link: http://amasci.com/miscon/whatis.htmlSorry for bringing it up again, but could you please clear this confusion
So "electricity" is not electromagnetic wave but it is electromagnetic energy ??
http://amasci.com/elect/elefaq1.html#aeFor the same reason, we will never find a simple answer to the question "what is electricity?" because the question itself is wrong. First we must realize that "electricity" does not exist. There is no single thing named "electricity." We must learn that, while several different things do exist inside wires, people wrongly call all of them by a single name.
"electricity" is a very vague term that doesn't mean anything specific. I would say it is mostly associated with how electromagnetism is useful to us humans. For example, it is used in terms like "electrical device". Also, it is strongly associated with electromagnetic energy because one of the important uses of electromagnetism for us humans is to turn EM energy into other forms (such as light).So "electricity" is not electromagnetic wave but it is electromagnetic energy ??
A given electrical device works on a fairly narrow range of currents and potentials as well as a narrow range of frequencies. It cannot utilize energy that doesn't match its operating specifications quite closely. Sunlight typically has frequencies much too high, and voltages and currents much too low.If electricity is electromagnetic energy, what is the need for photovoltaic ??
Cant sunlight for example be used directly as electricity ??
The main problem is not the size and structure of the "wiring" to contain the EM fields at light frequencies but the fabrication of diodes to convert the energy into a DC voltage like is done with utility frequency energy. Nanoscale EM structures can also be used to focus light energy to increase the conversion efficiency of some types of solarcells.
Generation planning: making sure there is adequate generation of the right type at the right place to serve future demands.That is interesting. What kind of electrical phenomena has a time scale of decades in power engineering?