Comment by roel_v | Hacker News Reader

Comment by roel_v | Hacker News Reader

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Maybe this is the right occasion to re-ask a question I asked some years ago on stack exchange, but (despite several people trying their best to explain) still failed to understand the answer to.

So: does electricity have 'mass'? What I mean is, when current flows, is there a transfer of electrons (or something else) from the power source to whatever it is send to? And is there a difference between AC and DC?

The context of this question is that the core argument of a legal paper (of all things) I was reading at the time (on property rights of virtual goods) hinged on there being a transfer of mass, however small. I wasn't so sure.

(my SE question devolved into a semi-legal argument - I have a law degree, the context of the question is a lot more nuanced still than the above description, and is very much tied to some specific 80 year old Dutch case law - just saying that to point out that a legal argument on whether or not the question matters won't add much to the discussion.)

Information has mass. Not much. Surely charge on a dram capacitor is s bit (oh the pun) of energy and energy is mass.

An excellent example of electron movement is a DC current in a metal plating tank or refining tank. Every atom of aluminum or copper or plated anything took the movement of precisely one electron (simplification because there are some non-electroplating methods for some base/plate combos, but yeah pretty much aluminium is a block of solidified electricity)

So take one RAM stick and another, with the exact same physical makeup (I know this is impossible, but for argument's sake). Now I put some information on the one, and random noise on the other. Both will have different mass, right (because there are different amounts of electrons in the capacitors of both)? Now I put valuable information on one, and I charge all capacitors of the other (so the second one has very information density, because it can be 'compressed' trivially by saying '4GB of high bits'). The second one will be 'heavier' than the first, right? And then I copy something over that second one. It's not like there is a 'transfer' of mass from the other medium to the RAM stack, because there is a net outflow of electrons, right?

Yes, there is a transfer of electrons from one place to another. It's not to the thing that does work, but through the thing that does work.

With a battery (DC/direct current), there's a surplus of electrons available at the negative end, a deficit at the positive end. The electrons flow through a circuit (from - to +) to perform work.

With AC/alternating current, the electrons flow in one direction, then the reverse direction several times per second. The purpose of this is to push energy further down transmission lines with less loss. Pushing DC from a plant to everyone's houses is very lossy.

Do electrons have mass? Yes. Does the circuit or device increase in mass when current is involved? No. You're actually not introducing additional electrons into the circuitry. The conductors and semiconductors already have electrons on the outsides of their atoms. We introduced an electron at one end, it hops onto an atom, pushing an existing electron over to the next atom and so on. It's the movement that produces "energy" and allows work to be performed.

Strictly speaking, you can hold extra electrons for short periods of time in capacitors, but the mass is so small as to be negligible.

Right, so, in an AC circuit, there is a movement of information without a net movement of the same elektrons, right? And it's (at least partially) the same electrons that jiggle left to right, right? So is it fair to say that in a DC circuit, there is movement of mass (although net, it balances out, because what goes in out on the left comes in on the right); whereas in an AC circuit, information is transferred just through the movement of the elektrons, but not through the elektrons themselves?

In 1975, our physics teacher said he'd been a consultant to the international group who was working on electric utilities and import/export of energy across the US/CA border. Trying to define what "electricity" actually was!

:)

Electric circuits are much like drive-belts, but using charged particles rather than rubber or leather. If a drive-belt extends across the border between two countries, what is being transported? It's not mass, since for every KG of rubber belt going out, an exactly equal amount is coming back. (Go further and use rotating shafts. Then the mass just spins in place, and doesn't actually cross the border at all.)

With circuits, with AC, the charges are just wiggling back and forth, and not proceeding forward. But with DC the charges are taking a closed circular path, so still are not proceeding forward. The thing which proceeds forward is radio waves. Sixty-cycle radio waves, forced to follow a waveguide composed of two or three conductors. EM waves are being sold to us by the utility companies. We live in a "radio-powered" civilization, but where the 60Hz EM waves are forced to follow waveguides, rather than leaping across empty gaps.

Humorous "legal" chapter in Feynman: IS ELECTRICITY FIRE?

https://www.reddit.com/r/atheism/comments/ev3gy/excerpt_from...

Not really.

Electrons do have mass, but a device powered by an electric current will generally have the electrons flowing out at the same rate that they flow in.

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