5 ms·

"they're just wiggling the electrons in your appliances back and forth" Sorry for highjacking your comment, but are there any physicists here who can comment o

by roel_v 10y ago

"they're just wiggling the electrons in your appliances back and forth" Sorry for highjacking your comment, but are there any physicists here who can comment on whether this is accurate? More in particular, does electricity have mass? Is 'current' electrons moving across a wire, or wiggling without 'moving'? I've asked this years ago on the physics stack exchange, but I never got an answer I actually understood. The context for my question was a legal paper I was reading whose core argument relied on 'current' having mass, or rather, the consumption of electrical energy requiring the transfer of mass, however small. Note that there is an important precedent in my jurisdiction (the Netherlands) that sort of assumed this back in the 1930's, but in this particular argument (on ownership of virtual goods, like a sword in World of Warcraft), the issue of the mass was even more pertinent. (note that I'm not interested in debating whether that matters re: ownerships of virtual goods; in my legal context it does. And yes I have a law degree. I'm just putting this in because I've asked several times in several places over the years, and there are always people who like to go 'XY problem!' and then make ridiculously wrong pseudo-legal arguments.)

maggit 10y ago
The comment is accurate, and electricity should not be considered as having mass. In a direct current (DC) setup, electrons will be moving continuously though the wires in a big loop. But the displacement of the electrons is not the electrical energy we are interested in. It is instructive to think about alternating current (AC). In this case, electrons will be moving a bit forward, and then a bit back. So, basically wiggling more or less in place. There is still a lot of energy transferred. A metaphor is a chain, like in a bicycle. You can use the chain to transfer energy, but it is not the chain links that are the energy. The movement is the energy. This is similar to electricity; it is not the electrons that move that is the electrical energy, instead the electrical energy is the movement itself. (Due to Einstein's theory of relativity, we know that E=mc^2, which can be summarized as "all forms of energy are also mass". Considering this, all transfer of energy is transfer of mass. But it is miniscule. A small nuclear power plant could produce 4450 GWh in one year. The relativistic mass of this is 180g. All the energy produced in one full year of this plant has a total mass of 180g. So you should not consider electricity to be transfer of mass, even though it technically is :P ) (Also, since you asked for a physicist: I am not a physicist)
- roel_v 10y ago
  No worries, I'm using a loose definition of 'physicist' - anyone knowing about physics is fine :) Thanks for your contribution; as I mentioned below, I've gotten some different answers, e.g. on http://physics.stackexchange.com/questions/2188/does-electricity-have-mass-is-electricity-tangible http://physics.stackexchange.com/questions/2188/does-electri... where I asked the first time. Essentially, are you saying that with DC current, there is transfer of 'mass', but with AC, there isn't? In the case such as I've explained it elsewhere in this thread, this might mean that it matters how a computer is build to decide on whether the virtual sword can be stolen or not... (maybe, I haven't really looked hard at it in a few years, so I'm probably forgetting some details of it).
  - IanCal 10y ago
    [Similar disclaimers about not being a physicist go here] Something that's going to be a bit tricky here is that electrons are really, really slow when we're talking about electricity through a wire. The electrons will bounce around very quickly at random, but the average flow caused by a current is slow. Really, really slow. https://en.wikipedia.org/wiki/Drift_velocity https://en.wikipedia.org/wiki/Drift_velocity For a specific but not unreasonable example: > Therefore in this wire the electrons are flowing at the rate of −0.000023 m/s. At 60 Hz alternating current, this means that within half a cycle the electrons drift less than 0.2 μm. In other words, electrons flowing across the contact point in a switch will never actually leave the switch. That kind of speed means that any messages sent over a copper wire are not going to be sending electrons all the way for that message. The electrons that 'carry' the message "I AM A VIRTUAL SWORD" will not go from my machine to yours as a rushing block. Instead all I'll be doing is tapping the end of a very long pole connecting our two properties, so you can read the message by the patterns of the end of the pole in your house moving ever-so-slightly. So, I guess I am transferring mass, but nothing that comes from me goes to you. This also assumes a very particular direction. There's nothing, as far as I'd understand, that requires me to be pushing electrons at you. I could be pulling on the pole slightly rather than pushing. I'd love any corrections or additions to this, purely my lay understanding of the topic.
    - 10y ago
avar 10y ago
Can you elaborate on the legal details of that 1930s case in The Netherlands please and how electricity being massless would change it.
- roel_v 10y ago
  First, note that that wouldn't change with electricity being massless; the argument in the paper I mentioned would. Turns out it was in 1921, but either way: there was a dentist who blocked his electricity meter by putting a pen in it (it was one of those that turned to take the measurement). The question was: did this qualify as 'theft', because, according to Dutch penal code, theft requires the 'appropriation of any good'. The argument was that electricity is not a 'good' (Dutch civil law has a particular concept of a 'good', and being physical is one of the criteria. Note also that I'm not writing a paper here, and that I'm using loose translations for terms that are well-known concepts, so I'm probably making several technical mistakes here). The Supreme Court however decided that electricity was still a 'good' because it represented economic value (that was one line of reasoning, they didn't actually say 'electricity has mass, hence it's physical, hence it's a good'). The paper I mentioned then concluded from this that the Supreme Court had decided that electricity has mass (because it was considered a 'good', and 'goods' need to be physical - which is why e.g. what we now call intellectual property is not a 'good'. This has far-reaching consequences.) So the paper went on to qualify virtual swords as goods, and then proceeded from there. There are more criteria for being a 'good', like something has to be uniquely identifiable; so the author couldn't make a straight analogy to the electricity case to make his case for virtual swords being 'goods'; I don't recall the details exactly but in the end, his qualification of virtual swords as 'goods' came down to electricity having mass. He said, essentially, that the 'sword' is the movement of electrons through systems, and that therefore it could be qualified as 'theft'. There was a separate argument about intellectual property as well of course, I don't recall either, but there was a reason that wasn't material in the precise question being asked. The whole point was of looking at the case of some people (physically) forcing a boy to transfer his virtual sword to them in some online game, and whether that constituted 'theft' or 'robbery' (which requires some aspects of the 'theft' aspect). (Edit: also, the paper was written by an engineer who also had a law degree (maybe this paper was part of his degree, I forgot.) This is not some case of 'haha idiot lawyer'.)
SamReidHughes 10y ago
See https://en.m.wikipedia.org/wiki/Electric_current#Drift_speed https://en.m.wikipedia.org/wiki/Electric_current#Drift_speed I think a decent analogy is a pneumatic air power distribution system. Air particles move randomly in the pipe, but if the air is flowing, they tend to pass through the customer in a given direction and get work done. Alternating current is akin to switching the direction of air pressure twice a day, from (say) 1.5 atm to 0.5 atm.
- roel_v 10y ago
  Well, when I asked before, people said that hydraulic or pneumatic systems are not apt analogies; because there is water, oil or water actually flowing. Now it's not the water that is the energy, it's the movement thereof, or the pressure. That's where the analogy starts to break down. For reference, the first time I asked was here: http://physics.stackexchange.com/questions/2188/does-electricity-have-mass-is-electricity-tangible http://physics.stackexchange.com/questions/2188/does-electri... (7 years ago - time does fly). There is a bunch of discussion there (also going into at what point a water analogy breaks down), and I'm not sure they agree with each other. I mean, another way of looking at it: you can encode n bits by charging (or not charging) capacitors. Does a series of capacitors encoding '0' have a lower mass than a series encoding '255'? So yeah I don't really understand, still not after all those years. It's probably (in part) because I have not formulated one single yes/no question that is unambiguous or does not need any interpretation to be answered. Or maybe I'm just stupid.
  - SamReidHughes 10y ago
    There is also electrons actually flowing. As far as movement of mass goes, the pneumatic system analogy is a good one. It is not a mathematically identical system. Look, you can just look at how this stuff works. Electrons move randomly, and when there's a current they move on average in a certain direction because the electric field leans that way. That's it. See my link I pasted above, it describes what happens when a current is flowing. A capacitor encoding '0' will have the same number of electrons as when it encodes '1' because that's the way capacitors work. You can read about it at https://en.m.wikipedia.org/wiki/Capacitor https://en.m.wikipedia.org/wiki/Capacitor
the8472 10y ago
Disclaimer: I am not a physicist. > the consumption of electrical energy requiring the transfer of mass, however small Does precedent talk about transferring mass of electrons? Otherwise the transferred energy also has mass, via mass-energy equivalence. > but in this particular argument (on ownership of virtual goods, like a sword in World of Warcraft), the issue of the mass was even more pertinent. This on the other hand is on a bit more tenuous grounds. In theory you don't actually have to move energy (and thus mass) around to move information if you use physically reversible operations. But all practical computers use irreversible operations, which means information is sent by expending some energy, this is obvious in sending photons down a fiber or radio waves being able to power a lightbulb. https://en.wikipedia.org/wiki/Landauer%27s_principle https://en.wikipedia.org/wiki/Landauer%27s_principle
pjc50 10y ago
This question, or variants of it, comes up on electronics.stackexchange a LOT. It's rather hard to explain in a compact way. You can either start with metaphors (which collapse under examination) or the maths (which most readers find impenetrable). Current is measured in amperes, which have two definitions: "a unit of electric current equal to a flow of one coulomb per second" "that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross section, and placed 1 meter apart in vacuum, would produce between these conductors a force equal to 2 x 10-7 newton per meter of length" Right away one of those definitions mentions charge (coulombs) and the other one doesn't. This is actually a better approach because while charge is usually carried by electrons, this is not always the case. Charge in semiconductors may be carried by "holes". Charge in batteries is carried by ions. Capacitors are usually considered to have a "displacement current" flow between the plates that has no carrier at all. HOWEVER! For the purposes of the question here, we can skip all that and focus on the electrons in your appliances. Specifically, we can see that there's a complete loop between them and the substation/pole transformer feeding your house. You have no direct connection to the HV lines. Perhaps you could say "the power company causes a magnetic force which moves the electrons in their transformer back and forth, which by electrostatics pushes the full loop of electrons in their and your wiring back and forth, which does useful work in your house". Simple.

by roel_v 10y ago

maggit 10y ago

The comment is accurate, and electricity should not be considered as having mass. In a direct current (DC) setup, electrons will be moving continuously though the wires in a big loop. But the displacement of the electrons is not the electrical energy we are interested in. It is instructive to think about alternating current (AC). In this case, electrons will be moving a bit forward, and then a bit back. So, basically wiggling more or less in place. There is still a lot of energy transferred. A metaphor is a chain, like in a bicycle. You can use the chain to transfer energy, but it is not the chain links that are the energy. The movement is the energy. This is similar to electricity; it is not the electrons that move that is the electrical energy, instead the electrical energy is the movement itself. (Due to Einstein's theory of relativity, we know that E=mc^2, which can be summarized as "all forms of energy are also mass". Considering this, all transfer of energy is transfer of mass. But it is miniscule. A small nuclear power plant could produce 4450 GWh in one year. The relativistic mass of this is 180g. All the energy produced in one full year of this plant has a total mass of 180g. So you should not consider electricity to be transfer of mass, even though it technically is :P ) (Also, since you asked for a physicist: I am not a physicist)

roel_v 10y ago
No worries, I'm using a loose definition of 'physicist' - anyone knowing about physics is fine :) Thanks for your contribution; as I mentioned below, I've gotten some different answers, e.g. on http://physics.stackexchange.com/questions/2188/does-electricity-have-mass-is-electricity-tangible http://physics.stackexchange.com/questions/2188/does-electri... where I asked the first time. Essentially, are you saying that with DC current, there is transfer of 'mass', but with AC, there isn't? In the case such as I've explained it elsewhere in this thread, this might mean that it matters how a computer is build to decide on whether the virtual sword can be stolen or not... (maybe, I haven't really looked hard at it in a few years, so I'm probably forgetting some details of it).
- IanCal 10y ago
  [Similar disclaimers about not being a physicist go here] Something that's going to be a bit tricky here is that electrons are really, really slow when we're talking about electricity through a wire. The electrons will bounce around very quickly at random, but the average flow caused by a current is slow. Really, really slow. https://en.wikipedia.org/wiki/Drift_velocity https://en.wikipedia.org/wiki/Drift_velocity For a specific but not unreasonable example: > Therefore in this wire the electrons are flowing at the rate of −0.000023 m/s. At 60 Hz alternating current, this means that within half a cycle the electrons drift less than 0.2 μm. In other words, electrons flowing across the contact point in a switch will never actually leave the switch. That kind of speed means that any messages sent over a copper wire are not going to be sending electrons all the way for that message. The electrons that 'carry' the message "I AM A VIRTUAL SWORD" will not go from my machine to yours as a rushing block. Instead all I'll be doing is tapping the end of a very long pole connecting our two properties, so you can read the message by the patterns of the end of the pole in your house moving ever-so-slightly. So, I guess I am transferring mass, but nothing that comes from me goes to you. This also assumes a very particular direction. There's nothing, as far as I'd understand, that requires me to be pushing electrons at you. I could be pulling on the pole slightly rather than pushing. I'd love any corrections or additions to this, purely my lay understanding of the topic.
  - 10y ago

avar 10y ago

Can you elaborate on the legal details of that 1930s case in The Netherlands please and how electricity being massless would change it.

roel_v 10y ago
First, note that that wouldn't change with electricity being massless; the argument in the paper I mentioned would. Turns out it was in 1921, but either way: there was a dentist who blocked his electricity meter by putting a pen in it (it was one of those that turned to take the measurement). The question was: did this qualify as 'theft', because, according to Dutch penal code, theft requires the 'appropriation of any good'. The argument was that electricity is not a 'good' (Dutch civil law has a particular concept of a 'good', and being physical is one of the criteria. Note also that I'm not writing a paper here, and that I'm using loose translations for terms that are well-known concepts, so I'm probably making several technical mistakes here). The Supreme Court however decided that electricity was still a 'good' because it represented economic value (that was one line of reasoning, they didn't actually say 'electricity has mass, hence it's physical, hence it's a good'). The paper I mentioned then concluded from this that the Supreme Court had decided that electricity has mass (because it was considered a 'good', and 'goods' need to be physical - which is why e.g. what we now call intellectual property is not a 'good'. This has far-reaching consequences.) So the paper went on to qualify virtual swords as goods, and then proceeded from there. There are more criteria for being a 'good', like something has to be uniquely identifiable; so the author couldn't make a straight analogy to the electricity case to make his case for virtual swords being 'goods'; I don't recall the details exactly but in the end, his qualification of virtual swords as 'goods' came down to electricity having mass. He said, essentially, that the 'sword' is the movement of electrons through systems, and that therefore it could be qualified as 'theft'. There was a separate argument about intellectual property as well of course, I don't recall either, but there was a reason that wasn't material in the precise question being asked. The whole point was of looking at the case of some people (physically) forcing a boy to transfer his virtual sword to them in some online game, and whether that constituted 'theft' or 'robbery' (which requires some aspects of the 'theft' aspect). (Edit: also, the paper was written by an engineer who also had a law degree (maybe this paper was part of his degree, I forgot.) This is not some case of 'haha idiot lawyer'.)

SamReidHughes 10y ago

See https://en.m.wikipedia.org/wiki/Electric_current#Drift_speed https://en.m.wikipedia.org/wiki/Electric_current#Drift_speed I think a decent analogy is a pneumatic air power distribution system. Air particles move randomly in the pipe, but if the air is flowing, they tend to pass through the customer in a given direction and get work done. Alternating current is akin to switching the direction of air pressure twice a day, from (say) 1.5 atm to 0.5 atm.

roel_v 10y ago
Well, when I asked before, people said that hydraulic or pneumatic systems are not apt analogies; because there is water, oil or water actually flowing. Now it's not the water that is the energy, it's the movement thereof, or the pressure. That's where the analogy starts to break down. For reference, the first time I asked was here: http://physics.stackexchange.com/questions/2188/does-electricity-have-mass-is-electricity-tangible http://physics.stackexchange.com/questions/2188/does-electri... (7 years ago - time does fly). There is a bunch of discussion there (also going into at what point a water analogy breaks down), and I'm not sure they agree with each other. I mean, another way of looking at it: you can encode n bits by charging (or not charging) capacitors. Does a series of capacitors encoding '0' have a lower mass than a series encoding '255'? So yeah I don't really understand, still not after all those years. It's probably (in part) because I have not formulated one single yes/no question that is unambiguous or does not need any interpretation to be answered. Or maybe I'm just stupid.
- SamReidHughes 10y ago
  There is also electrons actually flowing. As far as movement of mass goes, the pneumatic system analogy is a good one. It is not a mathematically identical system. Look, you can just look at how this stuff works. Electrons move randomly, and when there's a current they move on average in a certain direction because the electric field leans that way. That's it. See my link I pasted above, it describes what happens when a current is flowing. A capacitor encoding '0' will have the same number of electrons as when it encodes '1' because that's the way capacitors work. You can read about it at https://en.m.wikipedia.org/wiki/Capacitor https://en.m.wikipedia.org/wiki/Capacitor

the8472 10y ago

Disclaimer: I am not a physicist. > the consumption of electrical energy requiring the transfer of mass, however small Does precedent talk about transferring mass of electrons? Otherwise the transferred energy also has mass, via mass-energy equivalence. > but in this particular argument (on ownership of virtual goods, like a sword in World of Warcraft), the issue of the mass was even more pertinent. This on the other hand is on a bit more tenuous grounds. In theory you don't actually have to move energy (and thus mass) around to move information if you use physically reversible operations. But all practical computers use irreversible operations, which means information is sent by expending some energy, this is obvious in sending photons down a fiber or radio waves being able to power a lightbulb. https://en.wikipedia.org/wiki/Landauer%27s_principle https://en.wikipedia.org/wiki/Landauer%27s_principle

pjc50 10y ago

This question, or variants of it, comes up on electronics.stackexchange a LOT. It's rather hard to explain in a compact way. You can either start with metaphors (which collapse under examination) or the maths (which most readers find impenetrable). Current is measured in amperes, which have two definitions: "a unit of electric current equal to a flow of one coulomb per second" "that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross section, and placed 1 meter apart in vacuum, would produce between these conductors a force equal to 2 x 10-7 newton per meter of length" Right away one of those definitions mentions charge (coulombs) and the other one doesn't. This is actually a better approach because while charge is usually carried by electrons, this is not always the case. Charge in semiconductors may be carried by "holes". Charge in batteries is carried by ions. Capacitors are usually considered to have a "displacement current" flow between the plates that has no carrier at all. HOWEVER! For the purposes of the question here, we can skip all that and focus on the electrons in your appliances. Specifically, we can see that there's a complete loop between them and the substation/pole transformer feeding your house. You have no direct connection to the HV lines. Perhaps you could say "the power company causes a magnetic force which moves the electrons in their transformer back and forth, which by electrostatics pushes the full loop of electrons in their and your wiring back and forth, which does useful work in your house". Simple.