electromagnetic waves

shankbond

Joined Nov 4, 2007
53
can some body tell me what these waves are?

do they really are magnetic?
if yes then why arent they attracting iron objects towards them?

silvrstring

Joined Mar 27, 2008
159
shankbond, do you have something to upload?

shankbond

Joined Nov 4, 2007
53

shankbond

Joined Nov 4, 2007
53

thingmaker3

Joined May 16, 2005
5,073
They're called "electromagnetic" because they are comprised of both magnetic and electric fields. They don't draw iron toward themselves because the magnetic fields are in opposing directions along the wavelength.

Here's a picture: http://hyperphysics.phy-astr.gsu.edu/hbase/emwav.html

Dave

Joined Nov 17, 2003
6,960
can some body tell me what these waves are?

do they really are magnetic?
if yes then why arent they attracting iron objects towards them?

EM waves are self-propagating waves of orthogonal electric and magnetic-fields - one cannot exist without the other. In essence they are a form of energy that arises fundamentally from the EM-force (one of natures 4 fundamental forces).

As for magnetism, they will have an influence on magnetically permeable materials (via the magnetic field component). The structure and extent of influence is application and material dependant. When an EM-wave comes into contact with an iron object you must consider both the electric and magnetic field components.

Dave

theamber

Joined Jun 13, 2008
321
Actually there are 5 forces in nature the last being the Grand Unified Force or some call it the "Force" that is strong in Obione Kanobi.
To start properties of electric charges and magnetic fields are connected with the velocity of light! or lets say the velocity of electromagnetic waves because light is a form of a electromagnetic wave.
Electromagnetic forces donot attract any metals because they are too busy attracting each others changing polarities and interacting with the electric forces at the same time very rapidly. Remember that the poles of a magnet has to be alined in a certain way in order to cause attraction (like poles repels unlike poles attract). Actually electromagnetic waves are considered week quantized anyways.
Both Magnetic and Electric forces can be attractive and repulsive individualy. Imagine you are trying to charge a battery with AC, Can you? but it is a paradox if AC would be changing polarity at an infinite speed probably you could but we have a limit c.
Differences between Magnetic and Electric Forces:
- North and south magnetic poles always occur together
- Positive and negative electric charges can exist independently
Monopole magnets do not exist.
Now how is an electromagnetic wave. What can cause the acceleration of an electric charge?
Accelerated electric charges produce: Changing electric fields + Changing magnetic fields
Changing Electric and Magnetic Fields Interact: The electric and magnetic fields can create Electromagnetic Waves in which the two fields continuously produce each other as they move through space at 300,000 km/s. So I think that those are the reasons why EMWs do not attract metals but they do interact other ways with them.

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studiot

Joined Nov 9, 2007
5,003
Who says they don't attract metals, including iron?

Have you tried to calculate the magnetic field strength involved and comparing it with the field from a magnet that you can see move a lump of iron?

theamber

Joined Jun 13, 2008
321
Who says they don't attract metals, including iron?

Have you tried to calculate the magnetic field strength involved and comparing it with the field from a magnet that you can see move a lump of iron?
You mean that the magnetic field in a EMW is too small and that is why you cannot prove it through experimentacion.
It could be possible that EMW can produce some force upon microscopic metals particles.
Do you know of any experiments can you please elaborate more on this.

studiot

Joined Nov 9, 2007
5,003
Do you know of any experiments can you please elaborate more on this.
This is actually quite a complex subject as there are several variables/effects to consider here.

Firstly consider the relative size and mass of an iron atom and a photon.

If you stand on roller skates and push against a wall, Which will move?

You or the wall?

So the EM radiation may well be deflected rather than the iron.

This effect is well known and occurs for instance in the deflection of cosmic gamma radiation by the earth's magnetic field from the iron core.

Conversely if you have a fixed EM source of sufficient power light magnetic (compass) needles can be seen to be deflected. This can be observed near primary distrubution transformers and ELF broadcast earth stations.

*************

Another effect entirely is that EM radiation has variable wavelength, from a few atomic radii in size to thousands of kilometers. The magnetic field has a sine wave intensity distribution over this distance. It is also subject to the inverse square law.
Not only this but any traction exerted by this magnetic field will be in constant change as the field reverses with the cycles. The tractive effect from all complete cycles will cancel out over a complete cycle, leaving only the tractive effect of a residual part cycle that fits into the space considered.

theamber

Joined Jun 13, 2008
321
The magnetic field has a sine wave intensity distribution over this distance. It is also subject to the inverse square law.
I thought the inverse square law was overthrown long ago.
Not only this but any traction exerted by this magnetic field will be in constant change as the field reverses with the cycles.
That is exactly what I just said earlier.
As I also said that EMW interact with metals in many different ways as I also said earlier.
Look, the magnetic force on a moving charged particle is always perpendicular to the direction the particle is moving.
For example in a TV CRT the deflection yoke uses magnetic forces to steer the beam as the beam comes from the back of the tube to the front, up-down and left-right forces are needed for steering. But magnetic forces cannot be used to get the beam up to speed in the first place, since they can only push it perpendicular to the electrons direction of motion, not forward along it. Same as your compass example the forces are not attrative but are like a nuisance to the aligment of the needle that was being attracted by of the magnetic earth poles before the EMI disrupted it.
As you said it is a very lengthy subject, volumes have been written about it. But as answer to what the person bringing this post was asking. I think that EMW do no offer a kind of attraction as a permanent magnet will offer to a piece of iron.

shankbond

Joined Nov 4, 2007
53
thanks to all you guys ,

i just wanted to know that if i could produce and with a bit of manipulations i could control there magnetic force such as to focus there all energy to a particular point, this will save a lot of energy and will certainly limit the losses occuring in all electrical devices and also transformers.

theamber

Joined Jun 13, 2008
321
thanks to all you guys ,
i just wanted to know that if i could produce and with a bit of manipulations i could control there magnetic force such as to focus there all energy to a particular point, this will save a lot of energy and will certainly limit the losses occuring in all electrical devices and also transformers.
Absolutely the magnetism and light are the two subjects Einstain was really interesting in studying. Check this out:

http://www.magnetism.com/magblogarchives/2006/09/free_energy_forever_from_magne.html

studiot

Joined Nov 9, 2007
5,003
Look, the magnetic force on a moving charged particle is always perpendicular to the direction the particle is moving
And if the particles aren't moving and aren't charged?

I thought the inverse square law was overthrown long ago.
Are we having a serious discussion or just messing about here?

shankbond

Joined Nov 4, 2007
53
my friend i started , this discussion so as to gain some knowledege regarding how em waves work .

and after that i would have imagined an innovative idea to implement it

the discussion however did helped me but some points are still beyond the scope of my thinking ,so i can partially understand and partially not

any ways thanks for the help u guys,

now i think ,we should move this discussion on creating or knowing its more innovative aspects that have yet not been implemented .

silencer

Joined Jun 3, 2008
9
To start properties of electric charges and magnetic fields are connected with the velocity of light!
EM waves will propagate only at the speed of light in free space. In any other media they will be slower. And in some cases the phase velocity (the velocity of a particular point on the wave, say, its crest) can indeed by greater than the speed of light, but the group velocity (the velocity at which information is transmitted) will always be less than or equal to c.

Electromagnetic forces donot attract any metals because they are too busy attracting each others changing polarities and interacting with the electric forces at the same time very rapidly.
Electromagnetic forces interact with metals.

Remember that the poles of a magnet has to be alined in a certain way in order to cause attraction (like poles repels unlike poles attract).
A magnet does not have to be aligned in any specific way. The force produced by a magnet theoretically permeates all of the surrounding space, however at great distances it is assumed to be negligible. It is important to understand electromagnetics in terms of fields.

Imagine you are trying to charge a battery with AC, Can you? but it is a paradox if AC would be changing polarity at an infinite speed probably you could but we have a limit c.
Regardless of its frequency, AC will never charge a battery so long as it has no DC component. It has nothing to do with the physical limitation of EM propagation.

You mean that the magnetic field in a EMW is too small and that is why you cannot prove it through experimentacion.
If you want proof, go solve Maxwell's equations.

I thought the inverse square law was overthrown long ago.
If you are referring to the inverse square law for electrostatics, no. If you mean that the power in an EM wave falls off at a rate proportional to the distance from its source, no again. This is a property of any wave propagating as an ever-expanding closed surface, as it is inherent in the geometry.

As I also said that EMW interact with metals in many different ways as I also said earlier.
EM waves interact in just one way, as specified by Maxwell's equations.

But magnetic forces cannot be used to get the beam up to speed in the first place, since they can only push it perpendicular to the electrons direction of motion, not forward along it.
You are correct in that the force exerted upon a charged particle is perpendicular to both the particle's velocity and the direction of the magnetic field, however there is no reason why magnetic forces can't be used to get the beam up to speed. This is exactly how particle colliders work.

studiot and Dave have a good grasp on this stuff.....

silencer

Joined Jun 3, 2008
9
now i think ,we should move this discussion on creating or knowing its more innovative aspects that have yet not been implemented .
This is much easier said than done! The theory of electromagnetism is quite dense, and Maxwell's equations are not for the non-mathematically inclined to delve into.

Perhaps first we could discuss how the theory has already been used to implement some of the more prevalent machines used today, or explain some common phenomena.

studiot

Joined Nov 9, 2007
5,003
Shankbond

A good start would be to realise that EM waves are transverse waves. As such, they can take one of two forms of wave.

Travelling Electromagnetic Waves (TEM)

Stationary Electromagnetic Waves (SEM)

We also need to have a good appreciation of the range of frequency and wavelength involved. This can be found in almost every exposition of the subject and is called the elctromagnetic spectrum.

Finally we need to understand that EM waves are coupled electric and magnetic fields, with no charged particles involved. The electric and magnetic fields can and do interact with the rest of the universe in the normal way for such fields, but you have to take both time and scale into account to model these interactions.

The particulate aspect of EM behaviour is explained by photons which carry no charge. They also have zero rest mass and therefore zero mechanical inertia.

Once you understand these basic concepts you can build on them to make your model as (mathematically) complex as you like.