# Does 'electricity' have mass? Is 'electricity' tangible?

Background: I'm in a legal academic discussion about the status of electronic 'goods' and whether they qualify as 'goods' in the same way a chair and a pen do. In this context (and specifically at the exact circumstance under discussion), it matters if electricity is 'tangible'. So far, most authors have blindly assumed electricity to be a flow of electrons, making a literal analogy with water, making statements such as:

• Information is stored in capacitors in the form of electrons. When a capacitor is filled more than 50% with electrons, it's considered to be 'on' (a bit with value '1').

• The information represented by a certain current (or rather, a series of on/off currents) has mass, because it consists of the electrons that flow through the wire.

• A virtual object is tangible because it exists in memory in the form of electrons that are there (or not) in a certain pattern.

Now I have a background in informatics but only a basic knowledge of electricity, and as good as none on the fundamental (physics) level. However I still feel this representation is wrong, and that you can't just say that information in a RAM chip has mass because it consists of electrons that are or are not in the capacitors on that chip. I have found hints in that direction on sites such as http://amasci.com/miscon/eleca.html#made, but I can't quite make out what 'electricity' is and how it relates to current and potential and other words that are used interchangeably in these discussions but which are, I think, different things.

So my questions are (all just different angles of looking at the same underlying concept):

• What is 'electricity', really, on a fundamental level; but explained in terms a layman can understand? Is there an analogy with other things that is accurate, unlike the 'flowing water' analogy, which is sufficient for high school level but is a simplification? (at least, I think...)

• Do 'electricity', an 'electrical current' and an 'electrical charge' have mass, apart from the object they are embodies in? Does the mass of a copper wire change when you put a current through it, because of the electrons coming in and going out?

• How do electrons fit into this? Is electricity composed of a bunch of electrons that flow through a mass? I think not, reading the link I gave before, but I don't quite understand what their role is.

• Most authors blindly assume that electricity is merely a flow of electrons through mass. In how far and under what assumptions is this correct?

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I have often wondered the same thing about heat, energy, light/photons. –  JD Isaacks Dec 23 '10 at 18:12
One important thing to note, electric current is NOT the movement of electrons. In AC, the current alternates in direction resulting in no average movement in electron position at all, while AC does deliver power. You can better think of an AC as a movement of electromagnetic waves. Thinking of a flow of electrons should be the analogy of a DC. –  Cem Dec 23 '10 at 21:25
Thank you, this seems very relevant to my question. In how far are you in disagreement with the commenters below? Would you agree with the statement that an electric current has mass associated with it, or maybe that it is embodied by a movement in matter? –  Roel Dec 23 '10 at 21:40
@Cem: upon reflection, I'm not sure that's so accurate. After all, in AC, sure there is no net movement of electrons, but there is no net current either (according to the physical definition of current). –  David Z Dec 24 '10 at 7:10
@David: so you are saying that A in AC stands for "Absence of"? :-) Of course there is a current, although it is microscopic (in the same way oscillating point charge generates oscillating current and thus produces EM waves). But your statement can also be correct in the sense that average electrons' position doesn't change (is this what you are referring to by physical definition of current? I am quite unsure what the precise definitions are, to be honest). –  Marek Dec 24 '10 at 11:02

Interesting, but I'm don't think you are asking the right questions in the context of law.

The point is that electrons and electricity are completely irrelevant when it comes to the question of "tangible" and "electronic" "goods". You will obtain a good answer only if you forget about electricity, which just happens to be a convenient physical carrier of information, and focus on the objects that might or might not be goods like a chair or a pen. A proper question would be this: "Is a newspaper article a good, like a chair or a pen?". Specifying whether the newspaper article is written on paper or "on electrons" or on something else is besides the point because the concept of "newspaper article" is entirely independent of the material it is written on.

To put it more pointedly: if you have to know the metaphysical nature of electricity to make a law about newspapers, you're definitely doing it wrong. ;-)

Keeping in mind that your questions and their answers are completely useless in the context of law, I can now proceed to answer them.

1. I don't know of any good analogy to electricity that captures it properly. It is like gravitation in that distant bodies attract each other, except that in electricity, bodies can also repel each other. Furthermore, the gravitational pull of, say, a chair is so small that we don't think of a chair as attracting us gravitationally. This is also why the water analogy doesn't work so well: water does not attract other water from afar. The "cause" for attraction/repulsion is the electrical charge.

2. The carriers of charge, like electrons or ions (= atoms with electrons missing) do have a mass. You can think of them as tiny, charged balls flying around through space (keep in mind that a copper wire consist of mostly empty space, too). On the other hand, electrical current does not have a mass, just like a water current does not have a mass, it simply doesn't make sense. (Both imply a mass current, however.) Likewise, electricity is a general term and does not have a mass, just like "law" and "liberty" don't have a mass.

The mass of a copper wire is the sum of the masses of its constituents, some of which are electrons. However, the number electrons exiting a copper wire is usually the same as the number of electrons entering the copper wire, so its mass does not change. In any case, the mass of electrons is way too small to make more than a negligible contribution to the total mass of the wire anyway.

3. Again, "electricity" is a general term. The link you mentioned refers to electric current, which is the same as flow of charge. Basically, the link says that electrons are not the only tiny balls that carry a charge. This is indeed the case. It's just that in the common case of metals, electrical current is usually carried by electrons.

4. This question is not well-posed. Again, electricity is a very general term and encompasses things like electric field, electric current, electric charge etc. For instance, light is part of electricity as well, because it's an electromagnetic wave.

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I wanted to give you +1, but can you support your bold statement that what the OP is asking is useless in the context of law? –  ptomato Dec 23 '10 at 16:03
Well, it seems that the OP wants to find out whether information stored in a computer is "tangible" by learning more about the underlying physics. But as I argue in the second paragraph, this attempt is futile, because computers are just one representation of said information out of many. –  Greg Graviton Dec 23 '10 at 20:05
Thank you for your answer. I need to read carefully and re-read the link I posted to fully understand in the context of the argument re: 'virtual' goods as 'goods'. –  Roel Dec 23 '10 at 21:19
On the legal side, well a significant number of prominent scholars in the field disagree with you :) I think this is not the place for such a discussion, but I could summarize the arguments if you'd like when I have some time in a few days (I only have papers in Dutch making the case). There is much more to it than you imply, and much of it is quite technical (as in, 'legal' technical), and I wasn't convinced from the outset either if this question would matter, but I now think it does. –  Roel Dec 23 '10 at 21:23
@Greg: like ptomato, it seems rather strong to assert that the question is irrelevant in the context of law - I mean, I agree that it should be, but I guess the lawyers think differently. Anyway, +1 for the very detailed response which makes some great points I think. –  David Z Dec 23 '10 at 21:37

Electronic goods can be transmitted without exchanging electrons (think of wi-fi networks). They actually don't even need electricity at all, for example vouchers can be sent through normal post.

What changes is the configuration of electrons and electromagnetic fields in the electronic device which contains the goods. This is simply a "state". For example goods stored on your hard drive are merely stored as particular stable configurations of magnetic particles on a platter.

So in practice, electronic goods are merely numbers. There is no mass associated with them, and no particular exchange of charges. They are configurations, or states.

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I mentioned above that I wouldn't go into the details, but I've changed my mind a bit ;) The point the author who argued that virtual goods are 'goods' was making was that no, electronic goods aren't just numbers. They're a combination of data, stored in various places and transmitted in various forms, modified and rendered by the software context in which they live (the case was about things like swords in World of Warcraft). I'm almost at my character limit here, so I can't repeat the whole argument, but if there is sufficient interest I can summarize it elsewhere :) –  Roel Dec 23 '10 at 21:27
@Roel: When you buy a music CD are you paying for the physical plastic and aluminum disc or the information it contains? When you buy an mp3 from iTunes are you paying for the electrons or the information they represent? –  oosterwal Aug 31 '11 at 13:21

Electricity is just a generic term.

Electric current is a number representing the number of charged particles travelling through a given surface per time. Like how many women walk in the door to the mall in a given day, thats a number, it dont have mass. Electric charge would here be 1 if you are a women, and 0 if you are a man, the door would be the surface thorugh which we want to measure women current.

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Thanks. What would you call the charged particles? They're usually the electrons, right? So is it correct to say that electrons that are flowing through a gate on an IC are what constitute the state of the gate? That the 'state' of the gate is embodied by electrons, who have mass? –  Roel Dec 23 '10 at 21:31
1. No, electricity - or anything else in physics - can't be explained "completely accurately" in laymen's terms. Electricity is the simplest subgroup of electromagnetic phenomena which are caused by the electromagnetic field - an electric vector and magnetic vector that exists at each point of space and time - that is interacting with the matter. The electric charge is conserved and may be thought of as a kind of "material" but the analogy inevitably fails in many respects. In modern physics, electromagnetism arises from U(1) gauge symmetries that the laymen usually don't like to hear about.

2. The electric currents are all about moving electrons. The electrons' mass is about 1/2000 of the mass of the protons. But the density of electrons in a piece of material doesn't really depend on the current so the electric phenomena don't modify the mass. There is a small disclaimer: according to relativity, any form of energy corresponds to a mass according to the $E=mc^2$ formula by Einstein, so any energy - including electrostatic energy - increases the total mass of an object. But $c^2$ is about $10^{17}$ squared meters per squared seconds so the mass corresponding to a reasonable energy is just tiny.

3. Electrons are the only light charged objects inside the matter that may easily move. So if one wants to move the electric charge - what is known as the electric current - it has to be done through electrons. In principle, any other charged particle could do the same job but protons are heavy "cores" of the matter that is mechanically attached somewhere while other particles such as muons are unstable and they're not included in normal matter (at least not enough). Electrons are fundamental for electromagnetism exactly because they're the lightest electrically charged particles in the Universe (together with their antiparticles, positrons).

4. This is the same question. The electric current is by definition a transfer of the electric charge and the electrons are the only particles with charge that may be transferred through matter, so it is completely correct to say that in all regular materials, all electric phenomena boil down to motion - and interactions - of the electrons. Chemistry (and biology) boils down to the motion of electrons in electric fields, too. No disclaimers are necessary here: it is fully true for any situation that a lawyer could possibly encounter in his life.

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• This is directional movement of electrones in the field
• Electrons have a mass, but when current flows through a wire number of electrons does not change. They just move in the field, number is the same.
• Yes, it is. Electrons flow easily through metals in the presence of electric field, that's why they are conductive.
• Well, I think it's true by definition.

The only way you can increase/decrease mass of an object is when you charge metallic object - in this case count of electrons increases/decreases.

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I agree fully. Your charged capacitor has the same number of electrons as your uncharged one, its just that there is a surplus on one side and a deficit on the other. There is energy stored in the electric field, and by Einsteins e=m*c**2 this does have mass (but it is very very tiny amount). Like others I don't think the value in the electronics is the value of the materials. The value is a combination of intellectual property rights, and a share of very specialized capital manufaturing equipment. –  Omega Centauri Dec 23 '10 at 21:09
Thank you. It seems that is fair to say that the magnitude of an electric current is related to a movement of matter, and that a binary pattern therefore is 'tangible', in the sense that it has actual matter associated with it. Would you agree with me phrasing it this way? –  Roel Dec 23 '10 at 21:37
@Omega Centauri That's why I didn't mentioned capacitor, but a single metallic object. –  BarsMonster Dec 24 '10 at 4:52
@Roel: Yes, i think so. But it's really hard to see it :-) –  BarsMonster Dec 24 '10 at 4:54

At the risk of being redundant, I thought I would add my take on this:

• What is 'electricity', really, on a fundamental level; but explained in terms a layman can understand? Is there an analogy with other things that is accurate, unlike the 'flowing water' analogy, which is sufficient for high school level but is a simplification? (at least, I think...)

First, let me say that in physics, we don't really talk about "electricity" in general, because that word doesn't have a precise definition in physics. As far as we're concerned, usually, it's just the stuff that makes our computers work ;-) But I think if you really pushed a physicist to define electricity, they'd probably come up with something like "energy and/or information transmitted through the movement of electric charge."

I think the analogy of water might actually not be a bad one, but you have to get a little more general than just a simple flow through a pipe. For instance, one way to transmit information and energy through water is by sending waves from one end to the other. You could imagine dropping stones into a pond on one side of the pond, and a person on the other side could look at the pattern of ripples produced by your stones and read a message from them. Or they could set up a tiny water wheel that would be pushed by the waves, and use it to power some sort of device.

That's sort of like the way our electricity works, at least the kind we get off the public power grid. The water is analogous to electrons, and the ripples are like alternating current (so named because the direction of motion of the electrons - or water molecules - alternates back and forth as the waves pass by). Note that the water itself barely moves at all, it simply acts as a medium for the waves to propagate through. Similarly, with electricity as we typically use it, the electrons barely move at all, they simply act as a medium for waves.

• Do 'electricity', an 'electrical current' and an 'electrical charge' have mass, apart from the object they are embodies in? Does the mass of a copper wire change when you put a current through it, because of the electrons coming in and going out?

No.

Well... technically you could say that electricity has mass in the sense that running a current through a wire does add a tiny amount of energy to the wire, and when you measure mass (e.g. on a scale) you're really measuring energy instead. But detecting the difference in energy (mass) produced by an electric current would require a scale that is far more sensitive than any we have on Earth, and perhaps far more sensitive than any that we could ever build.

Think of it this way: electricity has mass only in the same sense that a person walking weighs more than the same person standing still.

• How do electrons fit into this? Is electricity composed of a bunch of electrons that flow through a mass? I think not, reading the link I gave before, but I don't quite understand what their role is.

Going back to my third paragraph, electrons form the medium that "electrical waves" exist in, just like water is the medium that water waves exist in.

• Most authors blindly assume that electricity is merely a flow of electrons through mass. In how far and under what assumptions is this correct?

This is not a correct description of the electricity we get from our public power grid. As I've said, that sort of electricity involves alternating current, in which the information is transmitted in waves, and the electrons simply form the medium for those waves.

However, there is another kind of electricity, direct current, in which the electrons actually do flow through the wire. This is what you get from batteries, for instance, and it also is used in parts of many electronic devices. Direct current would be analogous to water flowing through a pipe.

Both alternating and direct current are equally capable of transmitting information and/or energy.

P.S. For what it's worth, I once wrote a blog post addressing a similar question, namely how much the data stored on a hard drive would influence its weight. Hard drives basically use tiny magnets, not electric charges or currents, but the general idea is closely related. Note that the weight difference I calculated in that post (10-14 grams) is due to the energy difference between different ways the hard drive could be filled, specifically between two possible extreme configurations that are unlikely to ever occur in reality.

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Greg is completely wrong. Courts discuss the properties of electricity when deciding whether it is "tangible" or whether it is a "raw material." Why on earth would science be irrelevant to law?

The Alabama Supreme Court held as a matter of law that electricity produced by a power plant was "tangible personal property." 8 So.2d 521. A few New York tax courts have also held that electricity used in an electrolytic process is a "raw material" because the electricity has mass and electrons combine with the end product. 1990 WL 204901. The Mississippi Supreme Court, however, rejected the view of the New York lower courts and held that "since electricity is energy and has no mass or space, it cannot be a raw material." 670 So.2d 12.

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Great answer, thank you. This is exactly the question that was assumed to be true for the jurisdiction the article I mentioned was talking about, but imo it made some shortcuts there that I didn't quite agree with. The Miss. case is especially interesting to me for that reason. –  Roel Jan 27 '12 at 9:58
Sounds like the Mississippi Supreme Court missed mass-energy equivalence in their statement. –  Jason Waldrop Mar 19 '12 at 17:17

"What Is "Electricity"?" 1996 William J. Beaty http://amasci.com/miscon/whatis.html

"COME ON, WHAT IS ELECTRICITY, REALLY?" by Bill Beaty. http://amasci.com/elect/elefaq1.html#ae

When I hear the phrase "electronic goods", I think of physical, tangible objects such as AM radio receivers, cell phones, MP3 players, LCD wristwatches, the "Simon" electronic game, GPS receivers, etc.

Of course these physical objects -- what I call "electronic goods" -- are tangible and qualify as "goods" in the same way a chair and a pen do. Both these electronic goods and chairs are made of physical materials -- metal, plastic, etc. -- and require some skills and tools to manufacture. Both these electronic goods and chairs cost time and effort to acquire the raw materials and convert them into the final shape.

It sounds like you are also interested in "intangible goods", aka "digital goods", which can easily be perfectly copied digitally from any digital media to any other.

Such goods (songs in MIDI format, songs in MP3 format, software, news articles, photographs in JPG format, documents describing the exact shape of each part of a chair and how to assemble it, etc.) are in some sense "the same" whether they are printed with ink on paper, stored as magnetic patterns on a hard drive, stored in computer memory, (extremely temporarily) stored as fluctuations in photon density in space between a satellite in geostationary orbit and an earth station, stored as tiny dimples on a DVD, or stored in any one of a dozen other media.

Information can be stored in paper tape in the form of holes punched in the paper. When the left hole is punched, it's considered to be "on" or value "1". When the right hole is punched, it's considered to be "off" or "zero. (Standard paper tape has a different arrangement).

While the paper tape substrate has mass, the information represented by these holes does not have mass, because a spool of paper tape with some digital good stored on it weighs less than a completely blank (unpunched) paper tape. Also, if you start with two identical blank spools, and you put some valuable digital good on one tape, and completely fill the other tape with all-zeros (which has practically no value), the resulting spools weigh practically the same amount.

A virtual object stored on a spool of paper tape can be considered, in some sense, to be tangible because it is stored in the form of a pattern of holes punched in paper that can be seen and felt.

Since these digital goods can be so easily translated from one media to another, it doesn't make sense to me to focus on one subtle detail of the physics of one particular media, and assume that subtle detail has any relevance to the digital good -- when that detail is completely different when "the same" digital good is stored in a different media.

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Thanks for your answer David. True, one can have different connotations with a generic term like 'electronic goods'. I used it in the sense of a virtual item in a MMORPG or MUVE. –  Roel Dec 27 '10 at 14:30
(this 'post on enter' is getting annoying, how am I supposed to write paragraphs?) –  Roel Dec 27 '10 at 14:31
Anyway, your assessment is not quite accurate, since for the law it does matter if an item is 'tangible', because it allows a whole different set of operations to be applied to it. A 'good' is a very precisely defined concept and if a sword in World of Warcraft can be qualified as a 'good', it can be pawned, stolen, etc, all according to the rules of property law (again, all of this within my specific context, Dutch law, although there are crossovers to other systems). I will update here when I have a larger writeup of the argument somewhere else. –  Roel Dec 27 '10 at 14:35
• information is stored in capacitors in the form of electrons. When a capacitor is filled more than 50% with electrons, it's considered to be 'on' (a bit with value '1').

Incorrect. Information is stored in capacitors in the form of electromagnetic energy. It's also in the form of imbalance of electrons, not electrons themselves. To "charge" a capacitor, we take some electrons out of one metal plate and deposit them on the other metal plate. So, the number of electrons inside the capacitor never changes.

• the information represented by a certain current (or rather, a series of on/off currents) has mass, because it consists of the electrons that flow through the wire.

Incorrect, because the wires always contain the same number of electrons. The information is stored by having those electrons moving or unmoving. Analogy: a rubber drive belt is much like a current in an electric circuit, where the rubber is like the electrons. The electrons are there inside the wires, even when they aren't moving.

• a virtual object is tangible because it exists in memory in the form of electrons that are there (or not) in a certain pattern.

Incorrect. For example, in RAM memory, electrons behave analogous to beads on an Abacus. To store ones and zeros we flip the beads left and right. But we never add any beads to the abacus, or remove them. Only the pattern is important, not the beads. Digital information is like writing in sand, and we don't buy and sell sand, we buy and sell only the patterns. In RAM memory the total number of electrons never changes. But in each memory cell, in each flipflop, the electron flow is diverted to one of two possible paths to store one of two possible states: one or zero.

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"Incorrect, because the wires always contain the same number of electrons." But are the electrons always the same ones? I mean, a tube of water also always has the same amount of water particles (in an idea situation) - the ones coming out are replenished with new ones coming in. Is it the same with electrons? Do they go out the one end, and come in the other end? –  Roel Apr 18 '11 at 13:07
Right, it's just like a hose full of air or water. In any component or conductor, for every electron flowing into one end, another electron flows out the other. But also like water, the electrons are always wandering around at high speed, even when there is no net current. The electrons are like a cloud of buzzing flies, and when the entire cloud moves slowly along, that's the "electric current." –  william beaty Apr 25 '11 at 5:19

I agree with greg above, that the properties of electricity are irrelevant in law. There is (as far as I know) no good set of precedents/examples to quote.

The reason I justify my position is the electrons are not related to the good in any way, other than being a transmission medium. A newspaper article was not a great example, because the paper is always the same, it is attached to the good. Perhaps a closer example is saying a TV broadcast is not made valuable by the radiowaves it was broadcast on.

The electrons required (or not, see optical computing) to form a 'electrical good' are not constant - ie the same electrons do not remain as part of that 'good'

The thing that never changes, the basis of what that good is, is the coded description of it. The ones and zeros as Sklivvz put it.

Working out whether electricity is a physical thing is irrelevant, because the 'good' would theoretically be made of every electron in the world, as they could all be used at different times to make those ones and zeros.

The value of an electrical good as I see it is defined by 2 things - the intellectual property in it, and the accepted ownership of it. Like a famous painting the has been restored, you arent paying for the pigments, or even the brushstrokes.

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Electricity does have mass, yes.

Indeed, one of Einstein's 1905 papers, "On the Electrodynamics of Moving Bodies" specifically demonstrates this. A moving magnet becomes more massive due to its increase of energy, and this additional inertia causes its electric field to increase in strength as well. Hence E = mc^2.

If you wished, with sufficiently accurate instruments, you could measure your computer on a scale, and find the difference in weight when viewing different e-mails. The difference in weight, however small that might be, would NOT be zero. In 1971, two men, Hafele and Keating took a separate atomic clock onto a series of airliners going in opposite directions, and measured the difference between them. While in flight, the overall weight of the clocks was noticeably different. The force which causes an airplane to lift off is generated electrically, through the chemical reactions in its turbines.

So not only does electricity have mass, it is documented at least once in history that the amount of this mass has been measured scientifically.

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And I'll just add that there is no way to store information in such a way that it is massless. In the world of physics, there is no distinction between tangible and intangible materials. Everything that is observable is tangible, because if it wasn't, it wouldn't be observable. –  Andrew Mar 4 '14 at 5:35

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