Vee,
Yes…a static electricity field is a “perfect” electric field and a permanent bar magnet is a “perfect” magnetic field. When we do specific things to either, the other property pops out and is always ninety degrees offset from the other fields magnitude.
Earlier you mentioned we have a complex combinations of fileds in a cable. Reallt, at any point in time, we have to have but ONE signal or current magnitude. What gets gets that ONE signal, E or B field related, is a mess of stuff but the end result is always one thing at a time on the cable.
Look at any oscilloscope trace and we will see a SINGLE “line” (real squiggly up and down) on the dv/dt scale for instance. Never will we see more than one “signal”, they all get superimposed together…remember a square wave is a whole bunch of sine waves added up.
The amazing thing to me, is how we hear everything that is summed as though each is happening at the exact same time. But we think, how can that be with just one signal level representing ALL of the “sounds” that we hear?
You can tear apart a square wave to all the sine waves that made it and the same for any single voltage wave form. So we see one voltage but there are really many happening to make it. Physics doesn’t really exclude anything and it is like spaghetti sauce, it’s all in there.
I know this, but it is still hard to wrap your head around it.
As far as my take on cable elevaors, the magnetic field and electric field too, are influenced by the MATERIAL the field lines go through. If the material is different we have a change in that field from a low to high permeability materil’s properties; plastic verses low permeability metal (magnet will stick to it). We BEND the field lines by providing and easier, or harder, path of resistance or impedance to those flux lines.
We know this, but what we don’t know yet is the influence on the EM wave propagating down the cable at the dielectric’s seed relative to light (all audio cables have non linear velocity of propagation at all frequencies). How is the EM “signal” change with respect to time? THAT is the question. If it isn’t changed, we have no influence.
If I design a cable with a METAL foil all the way around it, and REMOVE it and test the cable each way, we DO INEED see an influence to the EM field (this example is using the electric field to change capacitance). We take advantage of this change to alter cable to have differing “impedances” to signal flow down the cable. 50, 75, 100 ohm type cables.
There are approximations that drop off, the metal has to be close enough to influence the cable and at some point moved away from the cable it is meaningless in real use terms but physics always hangs onto “some” meaning. When is a cable a UTP (unshielded) cable inside a metal building! We get hung up on that transition and not just with cable elevators. ALL of our equipment is in boundaries with other materials in the field lines on all the copper traces and wires in our boxes.
Digital removes the material influences and analog keeps adding them up. Digital’s LENGTH is changed by them so there is no great escape, but the distortion is removed at the lengths allowed by the influences of all the materials.
We need to define what we mean by meaningful! Physics in theory can ALWAYS show a change but can we hear the effect?
A UTP cable inside a metal building is UTP for all real purposes but to the pure theoretical physics it is shielded.
Best,
Galen Gareis
Best,
Galen