Yes, sadly, you are wrong. But it's not a strange error.
Electricity always flows in a circle(circuit).
And, in fact, in medical devices, transformers are often used to completely isolate devices from the line that they are plugged into. Electrons on the device side of the transformer will NOT try to flow back into the line side or an earth. They only want to flow back to the device side of the transformer.
Now, the issue is that when you want to create really strict isolation like this, suddenly all manner of things that normally you don't pay attention to suddenly become relevant. Is the device side of that transformer really not connected to the line side anywhere? No goop on the board? No water vapor? No lines that are a little too close? Is the hospital bed not connected to anything?
Guitar players who use tube amps and vocalists who use condenser microphones wind up with this issue all the time. Both the amps and the mics are "isolated" with relatively high voltage signals floating around--300-400V for amps:48V for mics--and consequently strange paths cause lots of "buzz" in the signal.
For example, the current into one terminal of a capacitor does equal the current out of the other terminal. Yes electrons are building up on one plate, but they're being depleted from the other - the net charge of the capacitor remains zero. If this weren't true, differently-charged capacitors would be physically attracted to one another!
If this goes against your intuition, it's because you've become so accustomed to this abstraction of ground which (mostly) lets you forget about the current flow on the other leg of the capacitor.
(In the electronics realm, the use of the term "ground" is much more casual compared to the NEC. To put it in terms of OP, "ground" in the electronics realm is more akin to the "grounded conductor", but alas could actually refer to anything you feel like thinking of as the reference.)
The realm of electrodynamics is pretty interesting, and it's where seemingly basic concepts like electric potential begin to fail -- it becomes path-dependent!
Not really. The problem is that we have sort of an "electron abstraction" which is incorrect in the Heaviside-Hertz pedagogy when fields start to store energy. I recommend "Collective Electrodynamics" by Carver Mead as a modern formulation without the silliness of an Aether: https://www.amazon.com/Collective-Electrodynamics-Quantum-Fo...
> I only brought up ground (in the Earth ground sense) because I've heard people think that antennas in general work by using the Earth as a second conductor, with EM radiation as the first.
Really? Most of the time I describe antennas as sort of really long range transformers. And, while you need each side of the transformer to be a circuit, the two sides of the transformer don't have to interact other than through a field.
> My previous comment was written out of a reasonably common conception of a closed circuit being a loop with constant current flow, but capacitors break such a circuit.
Yes and no. Capacitors have the hand wavy notion of "displacement current" in classical electrodynamics--but most of the issue is with the fact that we use the Heaviside-Hertz pedagogy which was formulated back when everybody believed in the Aether.
The real issue is that to deal with capacitors you must deal with fields rather than just the notion of electrons. However, if we kind of squint and wave our hands the "electron formulation" can be kinda sorta made to work. (Side note: Capacitive dividers are even more annoying and you have to be really careful.)
Classical Heaviside-Hertz electrodynamics also has a lot of issues dealing with motors and generators, as well. Again, the key is that an "electron formulation" isn't really enough when fields start holding an appreciable amount of energy.
(Re "not really": with Maxwell's equations, the curl of the electric field is generally non-zero, so scalar potentials are not well-defined, which is all I meant. My experience is having gone through Purcell long ago, and by now I have some familiarity with [mathematical] gauge theory, but really I'm only an E&M dilettante.)
Essentially, the ground rod acts as an "anchor" holding the neutral wire and the ground at the same electric potential. If there was no ground rod, the earth and the circuit would be "floating" relative to one another, and a dangerously large voltage could develop between them.
What a voltage does is pull or push the charge carriers. When lots of them flow, you have a current. Conductors, like a wire or ground rod, are full of free electrons to act like charge carriers (kind of like a pipe filled with water, the voltage is a pump that moves it).
The duality of pulling/pushing charge carriers is why we need a circuit. In order to push charge carriers, we need something to pull them from (a source) and somewhere to dump them (a sink). When we have no source and no sink, charge carriers have nowhere to come from and nowhere to go.
Ground is a convenient source/sink for charge carriers because it's roughly uniform in charge and huge, so pulling tons of charge carriers from it doesn't impact it greatly.
And it's not that charge carriers are always flowing back to earth, but back to their source. That's why ground is sometimes called a "return path." To move a charge carrier, you need to give it potential. It will lose that potential and return to the point of lowest potential difference from its origin - which is its origin.
But that said, for things like AC power, the charge carriers aren't actually moving very far at all and have a net displacement of 0. They vibrate adjacent charge carriers, and we convert that vibration into unidirectional (DC) voltages that can push/pull from local sources/sinks, be it the literal earth (mostly for safety ground) or a small plane of copper on a PCB.
> And it's not that charge carriers are always flowing back to earth, but back to their source. That's why ground is sometimes called a "return path." To move a charge carrier, you need to give it potential. It will lose that potential and return to the point of lowest potential difference from its origin - which is its origin.
The neutral lines of circuits are often tied into Earth, making the voltages of the neutral line and the earth equal to one another at what we've defined to be 0V (for reasons of convenience and safety). There's no intrinsic property of Earth that gives it a low electric potential, and electricity doesn't intrinsically want to flow back into Earth.