# Electric potential vs. current **URL:** \ **Category:** Factual Questions\ **Created:** [April 12, 2022, 10:58am UTC](https://boards.straightdope.com/t/electric-potential-vs-current/962715 "2022-04-12T10:58:55Z")\ **Posts on this page:** 20\ **Page:** 3
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [April 13, 2022, 5:11pm UTC](https://boards.straightdope.com/t/electric-potential-vs-current/962715/41 "2022-04-13T17:11:33Z")
What makes you think that the electrons don’t flow in a superconductor? > **[Electrons flow like a fluid in a metal superconductor – Physics World](https://physicsworld.com/a/electrons-flow-like-a-fluid-in-a-metal-superconductor/)** > > First observations of an electron–phonon liquid in a transition metal confirm theory predictions ---
**Author:** ![Crane](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crane/32/3495_2.png) [@Crane](https://boards.straightdope.com/u/Crane)\ **Post date:** [April 13, 2022, 5:17pm UTC](https://boards.straightdope.com/t/electric-potential-vs-current/962715/42 "2022-04-13T17:17:20Z")
My description was incorrect - sorry. Cooper pairs do move but without encountering resistance. So, how does a pulse flow? ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [April 13, 2022, 8:20pm UTC](https://boards.straightdope.com/t/electric-potential-vs-current/962715/43 "2022-04-13T20:20:58Z")
The same way as sound propagates through air. If I have a long cylinder with a piston at one end, and then push that piston in, air will leave the far end of the cylinder… But not instantly, not until after a time delay corresponding to the speed of sound. Meanwhile, you have some air molecules that are compressed together tighter than they ordinarily would be. Likewise, in a wire, electrons move, and bunch up until the electrons in front of them have a chance to move out of their way. ---
**Author:** ![Andy\_L](https://avatars.discourse-cdn.com/v4/letter/a/c67d28/32.png) [@Andy\_L](https://boards.straightdope.com/u/Andy_L)\ **Post date:** [April 14, 2022, 2:28am UTC](https://boards.straightdope.com/t/electric-potential-vs-current/962715/44 "2022-04-14T02:28:10Z")
So in an analogy of airflow to current, a piston that creates high pressure on one side and low pressure on the other is analogous to a battery, a steel plug is an insulator and a clump of steel wool is a resistor (a flexible plug is a capacitor just like in the water flow analogy). ---
**Author:** ![Crane](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crane/32/3495_2.png) [@Crane](https://boards.straightdope.com/u/Crane)\ **Post date:** [April 14, 2022, 1:47pm UTC](https://boards.straightdope.com/t/electric-potential-vs-current/962715/45 "2022-04-14T13:47:36Z")
> [@Chronos](#): > > The same way as sound propagates through air. Yes, sound propagates without transporting material from one place to the next. A sonic pulse will travel from one end of a, fluid filled, pipe to the other without inducing flow. Power lines are not highways that transport tons of material in the form of electrons. They are wave guides for distributing electromagnetic energy. An electric motor is not a water wheel. ---
**Author:** ![Crafter\_Man](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crafter_man/32/458_2.png) [@Crafter\_Man](https://boards.straightdope.com/u/Crafter_Man)\ **Post date:** [April 14, 2022, 3:13pm UTC](https://boards.straightdope.com/t/electric-potential-vs-current/962715/46 "2022-04-14T15:13:38Z")
> [@Francis\_Vaughan](#): > > The idea that the energy is only transmitted in the field outside the wire is a curious and it seems common misunderstanding of an idealised version of propagation. (Shades of a recent discussion about a video on the Veritasium channel on You Tube that got this badly wrong.) If the energy is not in the electric and magnetic fields, where else could it be? ---
**Author:** ![Francis\_Vaughan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/francis_vaughan/32/3093_2.png) [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)\ **Post date:** [April 14, 2022, 3:16pm UTC](https://boards.straightdope.com/t/electric-potential-vs-current/962715/47 "2022-04-14T15:16:12Z")
> [@Crane](#): > > Power lines are not highways that transport tons of material in the form of electrons. They are wave guides for distributing electromagnetic energy. An electric motor is not a water wheel. Again, it isn’t really clear what you are trying to say here. Power lines are most certainly not wave guides, at least not in any form that any RF engineer would understand the term. The wavelength of a 60Hz AC signal is 50,000 kilometres. Which is a few times larger than the diameter of the Earth. We can safely say that there are no waveguide related elements in the behaviour of any earthbound power transmission lines. There are issues with long lines carrying AC, but they are not waveguide behaviour. Given most power transmission is done with AC, the electrons involved in the transport of energy don’t get to move very far. But for a bit of fun, we can take one of the large DC power interlinks, and calculate what happens there. So, picking a family of pretty meaty HVDC interlinks built in China, they run at 500kV, and deliver 3000MW of power. Delivered with 6kA of current. 6 thousand Columbs of charge per second. It is that charge arriving with 500kV that delivers the energy. It is not the external electrical field of the wire, which on a DC transmission line is static. It is created as a side effect of the electrical potential along the length of the conductor. The field within the conductor is what is driving the electrons. The actual mass of electrons moved is tiny, and immaterial. Electricity is not about moving mass about. It is about moving charge, and when the charges are moving, the magnetic field that arises. Again, in a DC system, that magnetic field is unchanging, and does not move energy about either. In an AC power transmission line the period of the AC is so long that for the most part we can ignore the changing fields around the transmission lines. There are inevitable losses that do come about, but they are secondary to the overall power transportation. Even in our home, plugged into the mains, say a kettle will see of the order of a quarter of a Coulomb of charge move back and forth through the heating element on each cycle. That is a huge charge. An electric motor isn’t a waterwheel in so far as it doesn’t use gravity or the mass of moving charges to make it turn. A conventional electric motor is an electromagnetic machine, and uses electromagnets to transform changing magnetic fields into motive force. Faraday worked out how electromagnets work. You move current through wires. Again, it is the movement of electrons that does the work. A simple permanent magnet DC motor with a commutator is not that far from a water wheel. Electrons flowing through the winding of the electromagnets are immersed in a static magnetic field from the permanent magnets. They are arranged so that they feel a torque, and the commutator ensures that the torque always turns the same direction. The permanent magnets are akin to the Earth’s gravity, and the circulating currents in the electromagnets are like the water flowing over the wheel. Just a little more compact. There continues this undercurrent that energy does not flow in the wires but flows in the fields outside the wires. One can see where this misapprehension comes from. But in the case of power transmission systems it simply isn’t true. When you get into very high frequency systems, things become a lot more complex. (Pun intended.) In the extreme we used to joke that the real high frequency RF guys were those that basically considered any signal that would actually go down a wire as DC, and boring. But we are talking microwave engineering here. Much black magic to be found. In the middle we gets important problems like skin effect. But they only people that think that skin effect has any appreciable effect at any frequency less than radio frequencies are audiophool rip off merchants selling snake oil speaker cables. ---
**Author:** ![Francis\_Vaughan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/francis_vaughan/32/3093_2.png) [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)\ **Post date:** [April 14, 2022, 3:17pm UTC](https://boards.straightdope.com/t/electric-potential-vs-current/962715/48 "2022-04-14T15:17:24Z")
> [@Crafter\_Man](#): > > If the energy is not in the electric and magnetic fields, where else could it be? In the fields inside the conductor. I only said that the fields _outside_ of the conductor was not where the power transport was. ---
**Author:** ![komolono](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/komolono/32/532_2.png) [@komolono](https://boards.straightdope.com/u/komolono)\ **Post date:** [April 15, 2022, 5:48am UTC](https://boards.straightdope.com/t/electric-potential-vs-current/962715/49 "2022-04-15T05:48:56Z")
This is my final thought on this OP. No photons, because they don’t exist. But spinning electrons do exist - can electric potential make them spin faster - who knows - Chronos? Now if an electron spins faster, it is more likely to flow/drift away from the atom’s nucleus (like Levitron) to the next nucleus. No heating. But if you connect current sources in parallel, electrons don’t spin any faster there are just more electrons to collide and you need thicker wires. ---
**Author:** ![Francis\_Vaughan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/francis_vaughan/32/3093_2.png) [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)\ **Post date:** [April 15, 2022, 9:16am UTC](https://boards.straightdope.com/t/electric-potential-vs-current/962715/50 "2022-04-15T09:16:33Z")
> [@komolono](#): > > But spinning electrons do exist - can electric potential make them spin faster - who knows - Chronos? You can’t change the magnitude of the spin of an electron. All electrons have a spin of \frac 1 2. It can be up or down, but that is it. Spin has nothing to do with the external electrostatic field that an electron might be immersed in. That just acts to push the electron around. > [@](#): > > Now if an electron spins faster, it is more likely to flow/drift away from the atom’s nucleus (like Levitron) to the next nucleus. No heating. But if you connect current sources in parallel, electrons don’t spin any faster there are just more electrons to collide and you need thicker wires. Since the base assumption isn’t true, the answer is “no”. The binding of electrons in an atom is dependant upon a range of factors, and spin is one of them (spin is one of the quantum numbers that is folded into the Pauli exclusion principle and thus dictates how electron shells are filled.) Metals are a class of elements for which some electrons in the outermost shell are not tightly bound, and the atoms coalesce into a body held together by a sort of hybrid of covalent bonding and a sea of dislocated electrons surrounding the relatively positively charged metal atoms. The actual hybrid being dependant upon the individual elements present. The need for thicker wires is simply because of resistive heating. Moving electrons don’t move freely and as they are dislocated and move through the metal they dissipate energy into the metal lattice, heating it. More metal, the fewer electrons are trying to push though a given part of the metal, so the easier it is. Less resistance to movement and less heat dissipated, so the metal doesn’t get as hot. ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [April 15, 2022, 10:57am UTC](https://boards.straightdope.com/t/electric-potential-vs-current/962715/51 "2022-04-15T10:57:47Z")
> [@Francis\_Vaughan](#): > > But they only people that think that skin effect has any appreciable effect at any frequency less than radio frequencies are audiophool rip off merchants selling snake oil speaker cables. Skin effect is one of the reasons high-current busbars operating at just 50 or 60 Hz are hollow (to avoid wasting copper in the middle of the bar, where current density is low): > **[Busbar | Design and placement](https://en.wikipedia.org/wiki/Busbar#Design_and_placement)** > > The busbar's material composition and cross-sectional size determine the maximum current it can safely carry. Busbars can have a cross-sectional area of as little as 10 square millimetres (0.016 sq in), but electrical substations may use metal tubes 50 millimetres (2.0 in) in diameter (2,000 square millimetres (3.1 sq in)) or more as busbars. Aluminium smelters use very large busbars to carry tens of thousands of amperes to the electrochemical cells that produce aluminium from molten salts. > Busb... ---
**Author:** ![Francis\_Vaughan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/francis_vaughan/32/3093_2.png) [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)\ **Post date:** [April 15, 2022, 11:23am UTC](https://boards.straightdope.com/t/electric-potential-vs-current/962715/52 "2022-04-15T11:23:08Z")
> [@Machine\_Elf](#): > > Skin effect is one of the reasons high-current busbars operating at just 50 or 60 Hz are hollow (to avoid wasting copper in the middle of the bar, where current density is low): Yeah, I’ll give you that. There is a point where the losses from skin effect affect the economics of the design. What skin effect does not do is drive the power delivery into the field external to the conductor. ---
**Author:** ![Crafter\_Man](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crafter_man/32/458_2.png) [@Crafter\_Man](https://boards.straightdope.com/u/Crafter_Man)\ **Post date:** [April 15, 2022, 12:17pm UTC](https://boards.straightdope.com/t/electric-potential-vs-current/962715/53 "2022-04-15T12:17:51Z")
Skin effect is always “in play.” A wire operating at 2 Hz has slightly more resistance than the same wire operating at 1 Hz, regardless of its gauge. Of course, the decrease in resistance from 1 Hz to 2 Hz is very small, so we usually ignore it. The increase in resistance (compared to DC) due to skin effect becomes more and more significant as the frequency increases, and/or as cross-sectional area of the conductor increases. ---
**Author:** ![Crane](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crane/32/3495_2.png) [@Crane](https://boards.straightdope.com/u/Crane)\ **Post date:** [April 15, 2022, 1:12pm UTC](https://boards.straightdope.com/t/electric-potential-vs-current/962715/54 "2022-04-15T13:12:34Z")
How does electron flow explain data transmission down a wire pair or coax? Let’s say I have a series of data pulses traveling down a length of twisted pair that is properly terminated on both ends. The pulses are varying widths and spaces. Each pulse will result in current flow at the far end of the twisted pair. Each space will result in no current flowing through the terminating resistor. The length of the wire and the data rate is such that there is more than one pulse traveling down the wire at a time. If the data pulses (1) are moving packets electrons that carry information from input to output. Then the (0) pulses are non-moving packets that must also be carried from input to output. So, if you have a 101 data sequence on the wire, how is the 0 carried? ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [April 15, 2022, 1:19pm UTC](https://boards.straightdope.com/t/electric-potential-vs-current/962715/55 "2022-04-15T13:19:59Z")
The electric field changes. The motion of the electrons is pretty much irrelevant. The analogy I always liked was thinking of a wire as a tube filled with BBs, end-to-end, touching each other. Pushing a single BB into on end of the tube causes one at the other end to pop out. ---
**Author:** ![Crane](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crane/32/3495_2.png) [@Crane](https://boards.straightdope.com/u/Crane)\ **Post date:** [April 15, 2022, 1:27pm UTC](https://boards.straightdope.com/t/electric-potential-vs-current/962715/56 "2022-04-15T13:27:38Z")
> [@beowulff](#): > > other. Pushing a single BB into on end of the tube causes one at the other end to pop out. Good example of the electron flow analogy. It also illustrates why the analogy doesn’t hold for data transmission. How does the zero get transmitted through the BBs? ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [April 15, 2022, 1:28pm UTC](https://boards.straightdope.com/t/electric-potential-vs-current/962715/57 "2022-04-15T13:28:38Z")
BB = 1 No BB = 0. ---
**Author:** ![Telemark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/telemark/32/372_2.png) [@Telemark](https://boards.straightdope.com/u/Telemark)\ **Post date:** [April 15, 2022, 1:31pm UTC](https://boards.straightdope.com/t/electric-potential-vs-current/962715/58 "2022-04-15T13:31:30Z")
> [@komolono](#): > > No photons, because they don’t exist. Um, wait, what? ---
**Author:** ![Crane](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crane/32/3495_2.png) [@Crane](https://boards.straightdope.com/u/Crane)\ **Post date:** [April 15, 2022, 1:31pm UTC](https://boards.straightdope.com/t/electric-potential-vs-current/962715/59 "2022-04-15T13:31:38Z")
But with a 101 sequence, the BB and no-BB cases coexist. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [April 15, 2022, 1:32pm UTC](https://boards.straightdope.com/t/electric-potential-vs-current/962715/60 "2022-04-15T13:32:42Z")
No, there is time in between. BB pops out (time passes, no BB), BB pops out. 101 [Previous page](https://boards.straightdope.com/t/electric-potential-vs-current/962715.md?page=2) [Next page](https://boards.straightdope.com/t/electric-potential-vs-current/962715.md?page=4)