Jim,
Electric current is a flow of electric charge. Electric current produces magnetic field around the wire. Any change in amount or direction of electric charge produces a change in direction and amount of magnetic flux around the wire. Change in the amount of electric charge that flows in the wire, as well as amount of magnetic flux that follows, both change at the fraction of the light speed.
Presence of the load creates electric field between wires. Both electric and magnetic fields are necessary to transfer the energy from source to load. Both fields together create energy field (Poynting vector) toward load (that absorbs it), that follows changes at the same speed.
In case of the current thru the fuse, that was mentioned, energy field will be traveling thru all the space between fuse and the return wire. The further they are the larger this filed will be. It is wise to keep them close to reduce it.
As for the purity of the metal - the obvious thing is resistance of the wire, that causes power loss, less obvious is inductance of straight wire, affecting wire impedance, especially at higher frequencies (inductance is smaller for thicker wires). Second aspect of purity is that impurities in the wire reside between crystals of metal. Typical impurity of the copper is copper oxide (that is a semiconductor). What is audible, and what isn’t I don’t know. Often it is a placebo effect but I don’t mind. If placebo effect works it is worth the money :)
As for silver wire sounding different than copper - I have no idea. The obvious difference is lower resistivity of silver, but it is a very small difference. Silver, according to many, produces brighter sound. Maker of my cables, Acoustic Zen, adds few percent of copper into silver. To me it is all on the verge of black magic. |
Electric current in the cable is a flow of electric charge. Exactly the same amount of electric charge that leaves the source comes back to it. Energy is delivered from source to load by electromagnetic field in between wires. It is called Poynting field and direction of this electromagnetic wave can be determined by Poynting vector. Presence of the load creates voltage drop - an electric field between wires. Current in the wire creates circular magnetic field around it. These electric and magnetic fields are perpendicular. If you imagine them as X-Y axis then Poynting vector will be perpendicular to them as "Z" axis. This vector points always in the same direction, (from source to load) even with ac current, since both electric and magnetic fields change direction at the same time. In the coax cable, that was mentioned, whole energy (electromagnetic field) flows inside thru dielectric between wire and the shield. |
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"Way too much info"
Guilty as charged :)
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I would like to add, that it is as far as I can understand it and, of course, I can be wrong (I was wrong once in 1964) :) |
Electric charge moves together with electromagnetic wave at fraction of the speed of light in vacuum, dependent on dielectric (60-70%). What moves slowly in the wire is electron (drift velocity) - practically standing still at the audio frequencies. Electron doesn't have to be a carrier of electric charge - in water it is the ion. Electric and magnetic fields are constantly changing with alternating current, but energy is delivered on the outside of the wires from source to load (for AC and DC). The unit of Poynting Vector is "watts per square meter". Picture with battery and resistor illustrates this: https://en.wikipedia.org/wiki/Poynting_vector |
Is that the reason, say, a Teflon dielectric, insulation, will cause ICs to sound better than cheap PVC insulation? Capacitance between plates is proportional to overlapping area and relative permittivity while inversely proportional to distance. Relative permittivity of the material (also called Dielectric Constant) is a measure how fast given material can be polarized by electric field in comparison to vacuum. Permittivity is inversely proportional to speed of electromagnetic wave in material, squared. Speed of electromagnetic wave thru material depends on how fast material absorbs and releases energy (dielectric absorption). Because Teflon has low Dielectric Absorption electromagnetic wave travels faster thru it, than for instance thru PVC. As a result of it capacitance between Teflon wires is smaller than between identical PVC wires. Of course being straight proportional or inversely proportional is a simple equation for plates, but much more complicated for the wires but proportionality (dependency) is still the same. It is possible to lower Dielectric Constant of any material by foaming it or oversizing it around the wire as hollow tubes (air has lower dielectric constant than Teflon). My ICs have hollow oversized tubes made of foam Teflon resulting in 6.1pF/ft while typical wires have about 25pF/ft. |
An audio signal is purely a varying electrical voltage & current, just that . Nothing more.
Let me start simplifying it: INDIAN SEE EAGLE OVER RABBIT (instead of Ohm Law I=E/R) ;) |
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So the speed of the electric charge flow in a circuit is dependent on the connected load. The greater the load the faster the speed of the electric charge flows through the circuit. The speed of the electric charge is the same speed as the electromagnetic wave energy. Is that correct?
Jim, I might be wrong but as I understand it, the speed of electricity in the wire is very slow, since free electrons that carry charge move in random direction on its own and applying electric field (voltage) to a wire will direct them more in one direction (drift velocity). Amount of electric current will be proportional to number of electrons crossing any given point/plane. This number will be proportional to electric field (voltage) and the number of free electrons in given material (material conductivity). This is DC current. It produces magnetic flux around the wire. Product of this flux and electric filed creates energy field. All this is practically stationary and I'm not sure if amount of voltage applied changes speed, but for sure it changes number of free electrons crossing given plane (current). What moves fast is the change in electric charge. Free electrons in the wire (that repel each other) act like water in the pipe - you push on one end and water comes out instantly on the other end. Change in electric charge causes change in magnetic field around the wire resulting in energy field change (increase or decrease). This speed depends only on properties of material surrounding the wire. I know that electric and magnetic fields are always together. Flow of electric charge causes magnetic field while magnetic field induces flow of electric charge. We know that material itself (dielectric absorption) limits how fast magnetic and energy fields change, but I don't know how they affect back rate of change of electric charge. It might be because change in magnetic field produces back opposing electric field. At this point it is all getting very complicated - external magnetic fields, internal magnetic fields, inductance, eddy currents - skin effect etc. |
Slowly moving electrons represent electric current at DC. Electric current is amount of electric charge passing, per second. For the current to be 1 ampere electric charge of 1 coulomb (6.242 × 10^18 electrons) has to drift for 1 second (thru the plane). When electric field (voltage) changes (at AC), amount of "directed" free electrons in whole wire changes. As a result more or less electrons will cross given plane in time. Joules are just a measure of energy delivered to the load, equivalent to current of 1 ampere thru 1 ohm load for 1 second. This energy is still delivered on the outside. Power delivered by energy field is a product of electric field and magnetic field. Since electric field is proportional to voltage and magnetic field is proportional to current we say P = V x I (instead of measuring fields it is easier to measure what is causing them - voltage and current).
As I understand it, electric charge is carried by free electrons. Since free electrons always carry the same elementary charge then increase in electric charge means more electrons. Free electrons in the wire move randomly in all directions and are kept apart by repealing forces. Application of voltage directs some of them and they slowly move along the cable (overall motion of free electrons becomes less random). Applying higher voltage directs more of them in whole wire resulting in sudden change in amount of electrons crossing given plane in time (electric current). That would imply that electrons in thin wire move faster than electrons in thick wire, at the same current. I’ve read somewhere that this is the case. It is a little weird tough, because it means that electrons will accelerate thru the narrower part, like notched wire.
Again, it is how I understand it. Perhaps electricity, like a woman, exists to be loved (music) and not to be understood.
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