How is electricity transmitted thru light waves?

Are the photons themselves charged like electrons? Light is called electromagnetic energy. In what sense is it electrical OR magnetic without containing electrons?

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Light does not transmit electricity. Light is an oscillation of electric and magnetic fields.

 

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Photons do not carry charge.

It is an electromagnetic wave that propagates through free space (or through many materials.) It can be converted back to electricity through an antenna. In many cases (a microwave waveguide) it exists as sort of half "electricity" half EM field.

In my field we transmit power wirelessly by converting it to an EM field (primarily an M field) then converting it back to electricity with a receive antenna.

 

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.............The Electromagnetic Spectrum.............

links below may help you find your answers :

http://csep10.phys.utk.edu/astr162/lect/light/spectrum.html

http://missionscience.nasa.gov/ems/01_intro.html

http://www.newworldencyclopedia.org/entry/Electromagnetic_spectrum

Posting questions at SciForums seems be so much faster at producing true answers and much more reliable results than wasting hours or even days waiting for all that hogwash, that produces no results, that, it seems, one gets from the slow, unreliable and again seemingly, virtually, useless search engines.

Hope it helps

 

"Visible Light" refers to electromagnetic radiation with a frequency within a particular spectrum. Electromagnetic waves are transverse waves consisting of oscillating electric and magnetic fields that are always perpendicular and in phase with each other. Specifically, Faraday's Law and Ampere's Law with Maxwell's correction state that changing electric fields can generate magnetic fields, and changing magnetic fields can generate electric fields. Therefore, oscillations in the electric and magnetic field "feed off" of each other to allow an EM wave to propagate. More precisely, Faraday's Law states that ∇ X E = -∂B/∂t and Ampere's Law that ∇ X B = μ₀ε₀ ∂E/∂t in the absence of sources. By taking the curl of both of these, and using the vector identity that ∇ X ∇ X V = ∇²V - ∇ • V in conjunction with the other two Maxwell's equations, ∇ • E = ∇ • B = 0 (in the absence of charge), one arrives at the electromagnetic wave equations.

 

Tks..So light DOES transmit electrical energy as well as magnetic energy? Does this have anything to do with how light can generate electrical voltage on a solar panel?

 

Exactly. In an EM wave, half of the energy is stored in the electric field, and half in the magnetic field. The energy density of an EM wave, that is, the energy per unit of volume, is the sum of the energy densities contributed by the E and B fields. The former can be determined to be U = ε₀E²/2 from considering a simple capacitor, and the latter is found to be U = B²/2μ₀ by analyzing a solenoid. Therefore, EM radiation caries an energy density of

U = ε₀E²/2 + B²/2μ₀

By using the fact that, in an electromagnetic wave, the E and B fields are related by B = E/c, the above expression can be re-written as U = ε₀E² with some algebra. The power transferred through a surface by the radiation is then represented by the Poynting vector.

Well, you can think of it in terms of the conversion of electromagnetic energy (stored in the E and B fields) to the energy of the electrons in the solar cell in the context of the conservation of energy. The exact process makes use of the photovoltaic effect, which is very similar to the photoelectric effect that you may be familiar with from accounts of the history of quantum mechanics. The Wikipedia article summarizes the process well:

http://en.wikipedia.org/wiki/Photovoltaic_effect

 

Light has both a magnetic and an electric component. This is not the same as electrical current that you think of when you talk about electricity through copper wires, but is closely related.

Sort of. You are more using the energy of the photon to "kick" electrons across a gap, and the EM field of a photon is definitely related to the energy it transfers to the electron.

 

It isn't. But energy is.

No. In physics there's such a thing as pair production, wherein one photon gets "split and wrapped" to create an electron and a positron. Together the electron and positron has a net zero charge, just like the photon. There's also two-photon physics where you just "wrap" the photons to make the electron and the positron. In addition there's annihilation, where the electron and positron are converted into (typically) two photons. Net charge is conserved. It's like "charge is wrap". Or "winding" if you prefer.

Because it is comprised of displacement current, which is more fundamental than conduction current. Conduction current is essentially the motion of electrons. But in physics there's other currents.

Try to imagine that this is a picture of a particle. It's more complicated than an electron, but nevermind. If you move the whole thing you have a conduction current. But the particle itself is comprised of displacement current going round and round. The interesting thing about displacement current is that it's usually alternating. For an analogy, imagine a wave on the ocean, and you're in a canoe. As the wave passes you by you go UP. Then you go DOWN. A light wave isn't much different. Displacement current does what it says on the can. Have a google on light waves and alternating current. Look at google images. Also take a look at this:

"In electronics we control the motion of charged particles, but is this the only current available to us?"

The answer is no.

 

Radiation IS a form of energy. So no...no big difference at all. Here's some definitions I found in the web:

"Electromagnetic radiation (EM radiation or EMR) is a form of energy emitted and absorbed by charged particles which exhibits wave-like behavior as it travels through space."--Wikipedia

"Electromagnetic radiation (EMR) is a form of energy that is produced by oscillating electric and magnetic disturbance, or by the movement of electrically charged particles traveling through a vacuum or matter."

"The electromagnetic (EM) spectrum is the range of all types of EM radiation. Radiation is energy that travels and spreads out as it goes – the visible light that comes from a lamp in your house and the radio waves that come from a radio station are two types of electromagnetic radiation."

"Electromagnetic Radiation
Energy that comes to us from the sun is transported in the form of waves known as
electromagnetic energy."

 

MR, it's most accurate to say that electromagnetic waves carry a form of energy called "electromagnetic energy". Saying that something "is energy" is a habit that has essentially emerged from loose terminology. Energy is the capacity to do work in physics, there is no such as "pure energy", or similar terms often used informally. Since EM waves are oscillations in both the E and B field, they have the capacity to do work on electric charges - and thus contain energy. In a similar vein, work must be done to generate EM waves, and so they must carry energy.

 

Sorry..I'm sticking with the definitions given. One was from Goddard Space Science Center. Should we tell THEM they're mistaken?

 

Hi MarkM125, Magical Realist.

I naively understand that all 'energy' at the gross scales of thermodynamics and atoms etc is at heart 'e-m' energy, irrespective of the forms that energy takes on its way up through and down all the 'energy exchange/transformation' contexts/interactions which we call mechanical, chemical etc 'energy' form.

Underlying those various transformed energy labels, it all boils down to e-m 'energy' as such (again, I do not speak of the other non-em forms of energy below the usual gross e-m scales/forms).


Regarding 'energy' as such, I also naively observe that, basically, 'energy' is the original tendency to 'impetus' which arises from the energy-space itself, and manifests in the various higher dynamics forms as 'matter spin', inertial translation and e-m and other forms of that 'tendency to impetus' at the various scales. So 'energy' can be thought of as existing AS 'energy' per se, and all else is mere transformation/evolution depending of the dynamics/forms that energy is involved in from its original energy-space origins, up to complex contexts/dynamics, and back to original energy-space.

That's my two-cents observation/understanding re 'energy' and 'energy-space' per se. Good luck in your polite and interesting discussion!

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And I'll stick with definitions given in serious textbooks on the subject, rather than websites written for a popular audience. The following is from Halliday and Resnick, "Fundamentals of Physics", page 183:

From the same text, the following is from 1076:

Note that no vague references to energy are made: Maxwell's equations predict the electromagnetic waves, or equivalently, electromagnetic radiation.

 

Note the above definition given in post #15 from a textbook. Energy isn't a vague concept that needs a long philosophical elaboration. Only two statements need to be made: It's the capacity to do work, and it's conserved.

 

Yes, those (my bolded) textbook statements are already well known by me and everyone.

However, upon closer examination of those statements we see that they merely confine themselves to describing the 'consequences' and the 'constancy of quantity overall' without actual identification of what that energy is.

In no way do the statements actually imply or explain anything about the origins or nature of the energy itself.

That is why I proffered my naive and more 'basic' observation/understanding of 'energy' in my previous post:

I feel we as scientists need to do more than just be content with 'descriptive/predictive' labeling and modeling etc. We should actually explore more 'basic/fundamental' understandings of the real origins and nature of the 'energy' itself, irrespective of however else we may speak of it and use it. That is my naive goal in science; to understand more deeply and meaningfully, and not just 'label' things abstractly and move on. A valid goal for a scientist, Yes?

Thanks again MarkM125 and MR for your interesting discussion.

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Nothing in those definitions said EM radiation wasn't energy. Nice try though.

Here's a statement from a Navy electronics manual:

"EM energy is also called EM radiation, because energy radiates from its source."

Here's an opening statement from a NASA course on EM energy:

"When you tune your radio, watch TV, send a text message, or pop popcorn in a microwave oven, you are using electromagnetic energy. You depend on this energy every hour of every day. Without it, the world you know could not exist.

Electromagnetic energy travels in waves and spans a broad spectrum from very long radio waves to very short gamma rays. The human eye can only detect only a small portion of this spectrum called visible light."

Here's a statement from a University of Oregon online course:'"

"Electromagnetic radiation is energy that is propagated through free space or through a material medium in the form of electromagnetic waves, such as radio waves, visible light, and gamma rays. The term also refers to the emission and transmission of such radiant energy"

Encyclopedia Britannica anyone?

http://www.britannica.com/EBchecked/topic/183228/electromagnetic-radiation

Or maybe Dictionary.com:

"electromagnetic energy"
Part of Speech: n
Definition: "a form of energy that is reflected or emitted from objects in the form of electrical and magnetic waves that can travel through space
Example: There are many forms of electromagnetic energy including gamma rays, x rays, ultraviolet radiation, visible light, infrared radiation, microwaves and radio waves."

Definition of "energy" from About.com "Physics"

"Definition: Energy is the capacity of a physical system to perform work. Energy exists in several forms such as heat, kinetic or mechanical energy, light, potential energy, electrical, or other forms."

 

Repeat after me: electromagnetic waves carry a form of energy called electromagnetic energy. Energy is the capacity to do work, and so it makes no sense, none at all, to say that electromagnetic radiation "is" energy.

 

Perhaps the obvious 'apples and oranges' cross-communication can be short-circuited by asking naively:

What in and/or Where in does this "capacity to do work" reside for real (as distinct from definitional abstraction)?

And then you two can go again from your mutually agreed upon answer to that question?

Interesting discussion, guys! Thanks. Bye for now.

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