ElectroMagnetic Relationship

[DevilSolution]

This time im curious (confused) at how EM waves convert (relate) to other forces in engineering and physics. For example how much "Energy" does a transmitter emitting radio waves for satellite TV have in terms of firstly Energy in GR terms but also into other forces such as kinetic or sound??

 

Im mostly confused with [math]e=mc^2[/math] because photons seems to move at c but carry no mass, meaning, to my assumption, they also dont equate to an energy? ( [math]0 * C^2 = 0 [/math])

Also if you rearrange [math]e=mc^2[/math] equation so that we equate any EM pulse to some measure of joules (however small) then it calculates some mass even for a photon and its mass would be:

 

[math] m = J / sqrt(SOL) [/math] : i think? something similar anyway

 

The Joules will be converted from voltage/ampage that a receiver conducts from a radio wave, or more importantly a photovoltaic cell converts something apparently mass-less into an energy which is directly related [math] e = mc^2[/math]

 

Either way a definite mass should exist for the EM wave, or atleast thats how i perceived it given my limited knowledge.

 

Also can anyone use an analogy or clear cut explanation of what ER radiation is and how it works? Simplified to a form that is conceptual rather than mathematical, although ill still examine any formula's.

 

My current understanding is that Electro Magnetism is one of the 4 core forces in physics. Its the process of an elctronic wave and magnetic wave moving in inverse axis's somehow pushing the other along (like 2 cogs that move together). I've also been led to believe that in a vacuum all EM waves move at the SOL, regardless of its frequency or amplitude. I also know (or think, not sure about this one) that EM waves work within an atmosphere by creating a ripple effect on the electrons in an atom, but only in metallic elements that offer high conductivity or a magnetic field. Another thing ive been led to believe is that there's no absolute lower limit on the how quickly a wavelength can oscillate, which would mean the higher limit is defined by the SOL (higher limit is a wave that has been completely straightened, the lower limit a wave that keeps getting squished tighter and tighter?). The sun emits a varied array of EM waves that our ozone layer and natural magnetic core protects against. EM waves are illustrated using a sine wave. They oscillate once every period and the frequency is determined by how many oscillations the wave has finished in a second, measures in hertz. The height of the wave is called amplitude and it represents the pressure. The last thing i know about EM is that it is a form of radiation which means its not bound by alot of the laws of physics, it has no mass, will never end unless stopped by an object and is not bound to things like gravity (not sure about quantum laws, i have a question about this sentence) .

 

What force keeps the cogs moving at a constant rate? (as in why do the waves keep pushing each other without ever slowing)

 

Without any foreign body or object to obstruct it, would an EM wave continue infinitely?

 

Does an EM waves velocity change when inside an atmosphere and if so how ? (I.e smaller wavelength faster velocity etc)

 

What other physical laws are EM partial to? (thermodynamics, sub atomic etc)

 

Which side of the spectrum does the SOL reside?

 

Is there a difference between an EM wave and EM radiation? or is one a process of the other?

 

If the sun creates an array of EM waves and while also defining the sun being primarily (or originally) hydrogen based which we know means that every element known to man is just a hydrogen atom super heated and or compressed, does this mean every atom has some degree of electromagnetic induction and electrical conductivity? (or are they by-products of the heat / energy being used etc)

 

What or Where exactly does magnetism come from? (compared with gravity where we know two bodies of mass have a relative pull force (although we dont exactly know what creates mass))

 

Finally what, if any, relation does gravity and EM have?, Are they opposing forces? Or are they two completely unrelated phenomenon? (i predict the latter but dont understand why, i know they are both defined as one of the 4 core forces of physics but they seem to share the similar force of "pull" when analysing them both (the last statement somewhat implies that electromagnetism might create mass and gravity therefor a function / process of EM))

 

I've come to believe electromagnetism is one of if not the single most important concept is physics, however its also quite a challenge comprehending what it actually is and how it relates to other key concepts in physics.

 

Regards.

Edited March 25, 2013 by DevilSolution

[Mellinia]

http://en.wikipedia.org/wiki/Mass%E2%80%93energy_equivalence

You might want to check out the pc2 term behind E=mc2
E=mc2 is only for objects with rest mass not equal to 0.
For light photons it becomes E=pc, not mc2

[DevilSolution]

Cheers for your response, it makes sense that a mass should not be moving (having other forces act upon it) if you were to calculate its energy.

 

Quick dumb question though, what actually has a rest mass? i mean everything is always moving, after the apple hit newtons head it sat motionless but really it was spinning really slowly, we cant feel the earth move but it is and the sun is moving in the milky way and even the milky way is moving towards andromeda galaxy. I suppose something can have a highly accurate rest mass due to gravity but wouldnt gravity itself then become relative to the equation? i mean if you weighed an apple on the moon its rest mass would be different? Or is it calculated using atomic calculations?

 

Regards.

[swansont]

Either way a definite mass should exist for the EM wave, or atleast thats how i perceived it given my limited knowledge.

As Mellinia has already noted, there is more to the equation. E^2 = m^2c^4 + p^2c^2

What force keeps the cogs moving at a constant rate? (as in why do the waves keep pushing each other without ever slowing)

Basic Newtonian mechanics remids us that you do not need a force to move at a constant velocity.

 

Without any foreign body or object to obstruct it, would an EM wave continue infinitely?

Yes

Does an EM waves velocity change when inside an atmosphere and if so how ? (I.e smaller wavelength faster velocity etc)

 

Yes. The propagation speed is c/n in a medium, where n is the index of refraction.

What other physical laws are EM partial to? (thermodynamics, sub atomic etc)

The laws of electrodynamics are the ones that specifically apply.

 

Which side of the spectrum does the SOL reside?

Speed of light is not part of a spectrum.

 

Is there a difference between an EM wave and EM radiation? or is one a process of the other?

Basically the same. There may be circumstances where there is a distinction, but I can't think of any off the top of my head.

 

If the sun creates an array of EM waves and while also defining the sun being primarily (or originally) hydrogen based which declares that every element known to man is just a hydrogen atom super heated and or compressed, does this mean every atom has some degree of electromagnetic induction and electrical conductivity?

"super heated and or compressed" is off the mark, but yes. All substances will have a value for induction and conductivity.

 

What or Where exactly does magnetism come from? (compared with gravity where we know two bodies of mass have a pull force (although we dont exactly know what creates mass))

Magnetism is what happens when charges move in some way (or in the case of QM, have angular momentum). You get magnetic fields when you take an electric field and undergo a Lorentz transform, i.e. it's what an electric field looks like in another frame of reference.

 

Finally what, if any, relation does gravity and EM have?, Are they opposing forces? Or are they two completely unrelated phenomenon? (i predict the latter but dont understand why, i know they are both defined as one of the 4 core forces of physics, but they seem to share the similar force of "pull" when comparing magnetism to gravity (the last statement somewhat implies that electromagnetism might create mass))

Thus far they are unrelated. There may come a point where the forces are unified, but nobody has discovered the framework or the energy scale at which that happens.

[Klaynos]

To add to Swansont, I'd say em radiation implies propagation but em wave does not (standing waves are examples where this would be true). I'd also probably consider em radiation to not be coupled whereas em wave could be. In most circumstances the two are interchangeable.

[DevilSolution]

Cheers for the reply boss, it clarifies some of my questions so i have a clearer picture now.

 

I still didnt understand the explanation of magnetism or how a force isnt required to keep something physical moving at a constant rate, its probably due to the counter intuitive nature of magnetism and the intuitive nature that physical "things" need a force to be put into motion and continue.

 

I understand how electricity and magnetism relate, essentially existing as one force that interchanges however i still dont understand how a magnetic field exists in the first place, at the atomic level why do certain metals create this pull / push force? i think im confused because the nature of gravity is intuitive, theres no reason for 2 masses to attract but in a vacuum where only 2 objects of the same size exist it makes sense that a sort of suction would exist between them. Magnets dont need a vacuum.

Edited March 25, 2013 by DevilSolution

[elfmotat]

 

Thus far they are unrelated. There may come a point where the forces are unified, but nobody has discovered the framework or the energy scale at which that happens.

 

It may be a bit beyond what the OP has in mind, but classical unification of gravity and EM is very easy with various Kaluza-Klein theories.

[Klaynos]

You're trying to ask lots of questions in this thread some are classical some are not which is likely to confuse things.

 

There's no good classical model for how ferromagnetic materials are ferromagnetic. In the quantum world there are effects such as the spin orbit interaction, these are not something that can be easily understood even with a good qm background.

[DevilSolution]

Again im re-opening a dead post but i'd like 2 things clarifying that relate directly to this topic i already started.

 

First magnetism: Does magnetism work by much the same process as heat, such that one atom conveys no magnetic or heat properties but with a collection of atoms set with a particular configuration (electron polarity? (and kinetic rubbing of the valence shell electrons in heat?)) this then creates the phenomenon of the force??

 

And EM waves: How do we create radiowaves? something like the reverse of a dynamo?

[Klaynos]

A single atom can have a magnetic moment. In a bound structure you need these ,on average, to be aligned.

 

Most radio wave generators use oscillating electrons in antenna.