A question: the wire is considered a conductor, and free space an insulator. If a circuit is broken, say with a switch, current stops flowing. So why should the energy flow more readily through space surrounding the wire?
Could it be that both current and energy flow along the surface of the wire? Perhaps the electrons within the wire are unable to react because they are affected by neighboring atoms. That lattice of electromagnetic forces holds them in place. But on the surface, electrons can move somewhat. So the current and energy flow along the surface.
Consider a roughly circular circuit a mile or so in diameter—enough distance that there can be no direct electromagnetic interaction between the battery and the resistor. The energy presumably cannot flow directly across as per Figure 4.6 in Fields & Energy 4.1 Heaviside, Poynting, etc. So what does it do then? It has to follow the wire.
A basic principle in physics is action and reaction. The action is the charge differential at the battery. The reaction is the forcing of the charges through the resistor. Both are made up of electrical charges (I.e. matter). So how can the energy flow outside the wire when neither the source nor the sink are outside the wire?
Yes, current causes electromagnetic effects outside the wire. But I don’t see how electrical current in a circuit could be explained by energy flow outside the wire.
"It might even be questioned whether in electromagnetic phenomena the transfer of energy really takes place in the way indicated by Poynting's law… It must be observed however that there is no longer room for any doubt so soon as we admit that the phenomena going on in some part of the ether are entirely determined by the electric and magnetic force existing in that part. No one will deny that there is a flow of energy in a beam of light; therefore, if all depends on the electric and magnetic force, there must also be one near the surface of a wire carrying a current, because here, as well as in the beam of light, the two forces exist at the same time and are perpendicular to each other."
H.A. Lorentz (1853-1928) 1902 Nobel Laureate in Physics
The skin effect makes it pretty clear that the energy comes from outside the wire. Fields and energy work with charge to give rise to electrical effects. Yes, the energy follows the wire because the fields are strongest near the wire. The wire supports, guides, and sculpts the fields. It interacts with the fields through the behavior of the charges it contains. The key point is not that one is dominant and makes the other happen. It's that they work together. In field theory, there is a continuous chain of action and reaction from the battery, around the circuit, and to the resistor.
Minimizing AC resistance is one advantage. There are also mechanical advantages. Power cords are braided so they can be flexible and suffer fewer fatigue failures than the equivalent solid wire. Updated the post with a final paragraph to make that point clear. Thanks!
Just to be clear, litz wire is rarely used. Most stranded/braided wire is not litz wire. Stranded wire is used where flexibility is desirable. Normally braided wire is used in applications where it will be subject to movement or vibration, or in low-impedance RF circuits, etc. Litz wire is entirely different. It is expensive: it's used for special applications where you need to reduce the skin effect and distribute an AC current more uniformly on the cross-section of a wire, thus making more efficient use of the copper. It's an ingenious way to keep electrons from migrating to the outside edge ("skin") of the wire.
A question: the wire is considered a conductor, and free space an insulator. If a circuit is broken, say with a switch, current stops flowing. So why should the energy flow more readily through space surrounding the wire?
Could it be that both current and energy flow along the surface of the wire? Perhaps the electrons within the wire are unable to react because they are affected by neighboring atoms. That lattice of electromagnetic forces holds them in place. But on the surface, electrons can move somewhat. So the current and energy flow along the surface.
Thoughts?
Thinking about this some more…
Consider a roughly circular circuit a mile or so in diameter—enough distance that there can be no direct electromagnetic interaction between the battery and the resistor. The energy presumably cannot flow directly across as per Figure 4.6 in Fields & Energy 4.1 Heaviside, Poynting, etc. So what does it do then? It has to follow the wire.
A basic principle in physics is action and reaction. The action is the charge differential at the battery. The reaction is the forcing of the charges through the resistor. Both are made up of electrical charges (I.e. matter). So how can the energy flow outside the wire when neither the source nor the sink are outside the wire?
Yes, current causes electromagnetic effects outside the wire. But I don’t see how electrical current in a circuit could be explained by energy flow outside the wire.
"It might even be questioned whether in electromagnetic phenomena the transfer of energy really takes place in the way indicated by Poynting's law… It must be observed however that there is no longer room for any doubt so soon as we admit that the phenomena going on in some part of the ether are entirely determined by the electric and magnetic force existing in that part. No one will deny that there is a flow of energy in a beam of light; therefore, if all depends on the electric and magnetic force, there must also be one near the surface of a wire carrying a current, because here, as well as in the beam of light, the two forces exist at the same time and are perpendicular to each other."
H.A. Lorentz (1853-1928) 1902 Nobel Laureate in Physics
The skin effect makes it pretty clear that the energy comes from outside the wire. Fields and energy work with charge to give rise to electrical effects. Yes, the energy follows the wire because the fields are strongest near the wire. The wire supports, guides, and sculpts the fields. It interacts with the fields through the behavior of the charges it contains. The key point is not that one is dominant and makes the other happen. It's that they work together. In field theory, there is a continuous chain of action and reaction from the battery, around the circuit, and to the resistor.
I have seen braided wires all my life and never really thought about why they are braided, thankx for the enlightenment .
Minimizing AC resistance is one advantage. There are also mechanical advantages. Power cords are braided so they can be flexible and suffer fewer fatigue failures than the equivalent solid wire. Updated the post with a final paragraph to make that point clear. Thanks!
Just to be clear, litz wire is rarely used. Most stranded/braided wire is not litz wire. Stranded wire is used where flexibility is desirable. Normally braided wire is used in applications where it will be subject to movement or vibration, or in low-impedance RF circuits, etc. Litz wire is entirely different. It is expensive: it's used for special applications where you need to reduce the skin effect and distribute an AC current more uniformly on the cross-section of a wire, thus making more efficient use of the copper. It's an ingenious way to keep electrons from migrating to the outside edge ("skin") of the wire.
Youre welcome glad to help out
I had the exact same thought as I finished this one. Thanks!