Electromagnetic waves in metal

[mehboob_iiui]

HI, usual when I read about travelling em waves in a cable , I presume it travels in the form of current, am I right ..

also can electric and magnet fields not travel inside the cable as it does through the air,

or viceversa current through vaccum instead of em fields

 

[Element_115]

At higher frequencies the EM Wave travles on the surface of the conductor (metal).
Because the is less resistance.

In the real world all conductors have some small resistance, so if there is a
Current there must be a Voltage! V=IxR

 

[wandering heart]

Understanding by a current you miss lots of details, at least the field distribution, but maybe that's not what you care, then you are ok.

 

[dfullmer]

Hi guys,

Rf is not my strong suite but this is how antenna work for both broadcast and recieve isn't it?

regards

dfullmer

 

[sunroof]

Actually EM field is in the media between inner conductor and outer conductor of the cable. It is the EM field that is carrying the energy. There is no EM field inside conductor.

If the media between two conductors is vaccum, EM field will still exist.

I am not sure what exactly your question is.

 

[mehboob_iiui]

when we talk of wires, we consider that signal flows as variations in current, I wanted to know whether , current flows inside a coax cable or not.

 

[nijirazdan]

well theres no current involved in em wave propagation.energy flows here in form of electric n magnetic fields which travel orthogonally.

 

[djalli]

well theres no current involved in em wave propagation.energy flows here in form of electric n magnetic fields which travel orthogonally.

actually it is the current that is the energy not voltage. voltage is the force moving this current in conductor.

voltage comprises the force not actually move 100 electrons to move inside(actually on surface-read for skin effect in conductors) but this force makes sure that energy these 100 electrons are carrying is passed to next 100 neighbour electrons. this thermal-conductivity theory of metals

certain amount of energy is lost because metal has some resistance.

also can electric and magnet fields not travel inside the cable as it does through the air

electric and magnetic waves must ALWAYS co-exist together. I mentioned in quotes skin effect above. remember 100 electrons I mentioned above? their energy will decrea exponentially if current is attempted to travel inside conductor.

there is some rule, current/electrons will travel/pass their energies where is less resistance from their neighbor electrons. thermal-conductivity theory

In air(in vacum is the lowest) you have very little resistance. no wonder air/vacum is great for higher frequency em waves.

try high frequency under water. skin effect is a nightmare under sea level. its impossible. naval under-water transmissions are like 30hz waves.
1 page encrypted message needs 2minutes to get transmitted.

 

[rsrinivas]

hi all
pls explain me wat's voltage in practical words
not like it is the amount of work done in bringing a UPC from infinity.....

 

[nijirazdan]

well propagation of em waves thru metal is cretainly not desirable if it is to be seen a a propagation medium,skin effect plays havoc .