question about free space

Hi,

Dose free space resistes the flow of electricity, or dosent resiste at all?

Thanks

An electromagnetic wave will propagate(travel) through free space. There is some level of attenuation based on the distance from the source. I don't know that I've ever heard of this effect being associated with "resistance"

Electrons move through conductors and it is quite easy to see how current and voltage are related to "resistance". In semiconductors we again have electrons but also "holes". So electrons transport negative charge in the direction of travel, while "holes" transport positive charge in the direction of their travel. Various resistances come up in the study of BJT and FET circuits.

Thanks , but I mena, if I have a group of atoms containe extra electrons , and another group of atoms containe extra protons, if we placed them near to each other in free space, will the electrons flow from one group to another??

The unlike electrical charges will be attracted to each other. That is not a flow of electricity, though.

As we use it in AAC, "electricity" is the passage of electrons through wires and semiconductor junctions. A break in a wire effectively stops electron flow.

We rarely encounter free space - http://en.wikipedia.org/wiki/Free_space

Have a look at electronic tubes aka valves (as the UK'ers and Down-Unders call them), along with CRT's (cathode ray tubes).

In such devices, there is (at the most basic level) a cathode which is heated that emits electrons, and an anode (plate) which has a high positive voltage which attracts the electrons. The envelope for these devices is generally a glass tube which has been hermetically sealed at both ends. Before the tube is completely sealed, the air is evacuated as much as possible.

Such simple tubes were commonly used in radios and TV's as high voltage rectifiers.

Subsequent developments lead to control grids. A single grid can change the current flow from the anode to the cathode. Later, more grids were added to improve the linearity of the devices.

Electron tubes are quite interesting and historically very important.

fankoushat said:

Thanks , but I mena, if I have a group of atoms containe extra electrons , and another group of atoms containe extra protons, if we placed them near to each other in free space, will the electrons flow from one group to another??

Click to expand...

Yes, they can flow in principle, provided those charges can be liberated from the matter they eminate from. Vaccum tubes basically allow, and control, the flow of electrons in free space. Thermionic emission can liberate electrons from surfaces. At that point they can move under force from electric fields.

Free space does not have conductivity in any real sense. There are no free charges in free space, at least not intrinsically. Well, unless you count the spontaneous pair production and virtual particles. The interesting thing is that free space has a wave impedance (377 ohms).

Anyway free space is neither a conductor, nor an insulator because it is not a form of matter. It can not resist the flow of charges, so it's not an insulator. It can not provide mobile charges for a current path, so it is not a conductor.

Thanks alot guys, but is it right that conductors attract the electric field's lines, I mean if I have two groups of charges ( positive and negative) placed nearby to each other, there will be electric field lines between them through air, well, if we placed a conducting wire between them, will this wire attract these lines to its body(the wire material)??

Well, the electrons in the wire will be pulled from one field to the other, then the depleted electrons in the wire will grab from the positive charged field.