# The Naked Scientists Forum

### Author Topic: can electromagnetic field cross each other ??  (Read 1963 times)

#### ama

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##### can electromagnetic field cross each other ??
« on: 04/01/2012 06:50:46 »
hello ,
i'm wondering what if tow or more than electromagnetic field  cross each other what would happened on the middle ??

#### Soul Surfer

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##### Re: can electromagnetic field cross each other ??
« Reply #1 on: 04/01/2012 14:37:01 »
Electromagnetic fields are a linear process and as many as you like can cross each other without any effect other than local fields adding together.  you can easily see this by allowing two beams of light to cross in air with a torch or a laser.  if there is a non linear material where they cross however interesting things can happen where the frequencies of the two beams of light (assumed for the moment to be monochromatic) can mix together and produce sum and difference frequencies and sometimes higher harmonics of the original frequencies.  Thus is just the same as what happens in a simple superheterodyne AM radio but this is much lower frequency electromagnetic radiation.

#### Phractality

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##### Re: can electromagnetic field cross each other ??
« Reply #2 on: 04/01/2012 18:19:04 »
hello ,
i'm wondering what if tow or more than electromagnetic field  cross each other what would happened on the middle ??
[Disregard this paragraph.] Magnetic field lines, by definition, are perpendicular to the surfaces of equal magnetic potential. Crossing field lines would indicate more than one potential at the same location, which would be a discontinuity in the magnetic field. Our present understanding of magnetism is not compatible with such discontinuities. Perhaps it would be possible to construct a mathematical model of a distribution of magnetic monopole singularities which would result in such a discontinuity, but magnetic monopoles are still only theoretical entities.

Sorry 'bout that! My eyes saw the word "lines", which wasn't there.

Magnetic fields from different bodies add linearly at all points in their vicinity. However, each body may alter the magnetic characteristics of other nearby bodies. For example, soft iron in a neutral field may have no magnetic field of its own, but when it comes near a permanent magnet, the soft iron becomes magnetized. The combined field is then the sum of the permanent magnet's field and the induced magnetic field of soft iron.

The field that is induced in soft iron has the curious effect of canceling the field that would otherwise be present on the other side of the iron. A compass on one side of a soft iron plate will not be affected by a permanent magnet on the other side of the plate. The field inside a soft iron box is neutral, regardless of the presence of magnets outside the box. There is, however, a limit to how strong the magnet may be before the iron can no longer shield it field effectively.

Predicting the field that will result when permanent magnets and ferromagnetic objects are brought together requires high-level math and a knowledge of the materials as well as the geometry.
« Last Edit: 04/01/2012 20:45:04 by Phractality »

#### Soul Surfer

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##### Re: can electromagnetic field cross each other ??
« Reply #3 on: 04/01/2012 23:31:55 »
Phractality you are touching on a point that I was considering mentioning before I gave the simplest answer.  When a rotating body or an eddy in a plasma has a magnetic field it can restrain the filed and twist the lines of force and stretch them to store up energy from the rotation. These will at some point break and snap back releasing the energy.  This also is a non linear process and is seen as the source of solar flares and coronal mass ejections from the sun.

#### ama

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##### Re: can electromagnetic field cross each other ??
« Reply #4 on: 06/01/2012 07:05:03 »
i have something else , what if we make some kind of machine that look like the atom , with an orbit that produce the electromagnetic field , and these orbit are rotating and moving ( just like the electron on the atom ) , what will happen on the middle of these orbit , and if we some kind of material like an iron what will happen to it .

#### Soul Surfer

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##### Re: can electromagnetic field cross each other ??
« Reply #5 on: 06/01/2012 08:53:24 »
we use them every day they are called electromagnets :-)

#### ama

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##### Re: can electromagnetic field cross each other ??
« Reply #6 on: 06/01/2012 10:31:57 »
i don't understand ???

#### Soul Surfer

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##### Re: can electromagnetic field cross each other ??
« Reply #7 on: 07/01/2012 23:14:57 »
I thought that you were joking.  Just in case you really don't know here is an explanation

What you are describing is an electric current going round in circles.  That is exactly what happens with a coil of wire with a current flowing through it.  This creates a magnetic field along the axis of the coil.  If you stick a piece of iron in the middle of the coil this enhances the field in the coil.  Devices like this are used as electromagnets and in electric motors and have been commonplace for more than one hundred years.

#### The Naked Scientists Forum

##### Re: can electromagnetic field cross each other ??
« Reply #7 on: 07/01/2012 23:14:57 »