You bring up a good point. You cannot have a current source without a driving voltage and vise-versa. The terms are just approximations used in Engineering. If we have a source of energy connected to a load and the load resistance changes, if the current changes significantly compared to the voltage we have a 'voltage' source. If the voltage changes significantly compared to the current we have a 'current' source. But naturally there is no perfect voltage or current source, thus in reality both voltage and current 'sources' are actually a mixture of the two.
A bench top power supply with current limiting can be thought of as a voltage source, (when the current is below the set limit) or as a current source (when the current is above the set limit). I have used bench power supplies for both scenarios. So here we have something that can be either pending how you use it.

Yes and i think a solar cell is considered a current source in it's most basic form but it's a bit more complicated too.

All this is till a bit after the fact though as this thread was meant to address a different issue one that is more basic than a current source or voltage source. The physical view maybe makes this more apparent with teh force and mass example.

When we use a force to push a mass that is not moving yet, we want to look at the very instant of first contact. We dont look at where the force came from, we just look at what happens at that very instant when the force starts to act on the mass. Anything before that is moot. Now i realize that is not the typical view we take because we are after all humans and we tend to attach nouns to things in order to simplify a discussion. For example we may state that the mass beings to move AFTER the force is applied. But that's only when we look at this as if the force being brought into contact with the mass has something to do with it, but that's only true because we "regard" it as being that way, and that's not what i wanted to point out in this thread. The point here is sort of 'after' the force has been applied but only an infinitesimally short time after the force has been applied and in electrical theory we would state this as:
t=0+
where the little plus sign (usually nearer to the top of that zero) indicates we are looking at a time that is really t=0 but we need a way to indicate that there is some initial value.
For example, "A switch closes at t=0 what is the current at t=0+".
And if we do a simple equation of motion on the mass, we see that when there is only mass involved it begins to move at t=0+ even though the initial value is 0 distance. A mathematical view of this would simply say that the although the distance is zero, the first derivative is non zero.

 

Yes and i think a solar cell is considered a current source in it's most basic form but it's a bit more complicated too.

A photo current does exist only when the solar cell is part of a closed loop consisting of a conductive material.
Under open-loop conditions such a device produces an (open loop) voltage. Hence, it is a voltage source.
Therefore, several solar cells can be combined in series for producing a larger voltage.

 

If you consider how the entropy occurs we observe that there are charge separating mechanisms that occur naturally.
Keeping this simple since the junction of a semiconductor and the convergence of light are more complex than what is needed.

A small charge on a (conductor) metal plate distributes evenly. A geometry is formed on the surface, when describing this as an ideal model.
The displacement of charge on the conductor involves some movement. The electrons and protons are said to move (exchange) on the lattice.
When the charges cover the surface a second layer's geometry and dimension somehow form into a 3D spatial lattice. The lattice electrons
and protons are not alone in this process. The charge is usually referenced at ground state measuring a few femto-Farads.
In the simple demonstration below, potential energy facilitates charge separation when a polar material is in proximity to a conductor
it's surface acts as a storage. It is not the charge alone but the action of the polar materials separating the positive and negative charges.

Charge separation was observed and then Coulomb's law quantified it. If you notice the E-field of the aluminum can, we observe
that when we employ a variety of materials having different charge affinities a multimeter is not necessary. It was the material's electrical properties.
Which picture denotes the correct answer? Without imagery charge separation and the formation of a dipole would be more difficult to understand.
When the charges separate then there is movement, this results in forming a dipole in a conductor. This why we can say voltage is first because it is the result of a movement of charge q+ or charge q-

 

If you consider how the entropy occurs we observe that there is a charge separating mechanism.
Keeping this simple or you will get lost in the forbidden zone of a semiconductor.

A small charge on a (conductor) metal plate is distributed evenly. A geometry is formed as an ideal model.
The displacement of charge on the conductor, involves some movement. This is a molecular movement on the lattice.
Next the second layer's geometry and dimension may need to improvise somehow. The lattice electrons
and protons are not alone. The charge can be referenced usually at ground state give or take a few femto-Farads
the addition of charge continues, it is facilitated by a charge separating mechanism and not the charge itself.
At this point it becomes necessary to introduce either photons or phonons and the dimensional change is better referred to as a field.

Yes looking at the fields is a better way to look at it that's why i started talking about it earlier and introduced the Poynting vector. If there is a flow of energy, even a tiny amount, then there has to be both an electric field and a magnetic field. That's not to say though that they will be equal in any sensible way. In some applications one will be very low while the other very high but we sometimes think of one being more influential than the other while the fact is that they must both be present. Everything else is sheer interpretation.

We end up with two interpretations for the bipolar transistor one being voltage controlled and the other current controlled in a similar manner. It appears that the voltage has to overcome the bang gap potential but that's internal to the transistor not external. To get that 'buildup' we again have to have both even though one may be much 'smaller' relatively speaking than the other.
I think this may point out a major problem because it appears that the voltage is somehow building up all on it's own, but we all know that voltage can not build up without moving charge, and that brings us back to the simultaneous issue.

 

In quantum world, all of known presumptions would be contravened,
for example wonder if you could define a particle for voltage and one other for current,
just like they talk about a particle for time!
so ,independency would be applied for both concept.

 

voltage is a term that is relative
current denotes a direction or source to sink

I wonder is current our electrical definition of a meaningful directed movement?

electron Movement is always present above absolute zero. Isn’t that current? A net current may be zero as well as net potential for a given object or system.

just some more perspective. Very good and healthy conversation, thank you @MrAl

 

electron Movement is always present above absolute zero. Isn’t that current?

The answer to this question is very simple: It is a matter of definition.
I think in the engineering sense this is not that quantity we call current.
This is the background and the reason for the statement (in the engineers world) : No current without a driving voltage.
On the other hand - is there any term or word for the movement of charges due to other reasons (e.g. chemical processes or diffusion caused by unbalance of charged particles)?

 

In quantum world, all of known presumptions would be contravened,
for example wonder if you could define a particle for voltage and one other for current,
just like they talk about a particle for time!
so ,independency would be applied for both concept.

Well as far as a know, the electron is the particle in question. Recently though it has been split into two particles one for negative charge and one for spin. Whether or not that holds over time we have yet to see but it has been thought to have been true for many years and just sort of recently has been observed.
It could be just under extreme conditions however so it may not always apply.

In the theory of charge as an electron as the quantum though the charge has both electric and magnetic properties and doesnt loose them. It makes sense then that when a charge movies it is going to alter the perceived voltage across two points unless the charges move in perfect unison and symmetry.

Yes quantum mechanics is changing literally everything even cause and effect. If the effect can come before the cause, there's no longer any meaning to cause and effect.

 

voltage is a term that is relative
current denotes a direction or source to sink

I wonder is current our electrical definition of a meaningful directed movement?

electron Movement is always present above absolute zero. Isn’t that current? A net current may be zero as well as net potential for a given object or system.

just some more perspective. Very good and healthy conversation, thank you @MrAl

Yes i see what you mean. But i think that at the most basic level we can say that if charge is moving there has to be a voltage potential difference and that would apply to both ordered movement and random movement.
One way to look at it may be that of a bar magnet (or ball magnet) that also has a voltage potential across it. The potential will interact with other potentials while the magnetic field will interact with other magnetic fields, but we wont see an external net magnetic field until the random movements become ordered as then the individual fields do not cancel out but start to act together.
Microscopically it would be random with some order to it while macroscopically it would appear as a uniform magnetic field externally.

Yes it turned out interesting with all the different ways to view current and voltage.
I guess my main point boils down to the idea that the mere application of a voltage does not constitute cause (of current flow).

 

A photo current does exist only when the solar cell is part of a closed loop consisting of a conductive material.
Under open-loop conditions such a device produces an (open loop) voltage. Hence, it is a voltage source.
Therefore, several solar cells can be combined in series for producing a larger voltage.

Just because I can :->

is this an example of something like Schrodinger's cat ?

where it might be, but till you measure, and I assume by definition you need current to flow to measure,
it might not be !


Not thought about it before,
interesting ,

 

Just because I can :->
is this an example of something like Schrodinger's cat ?
where it might be, but till you measure, and I assume by definition you need current to flow to measure,
it might not be !
Not thought about it before,
interesting ,

Is this a serious comment? I cannot see any relation to Schrödinger.

 

Is this a serious comment? I cannot see any relation to Schrödinger.

serious ish
the voltage might or might not be there,
we can't tell till we take a current from the source to measure it !

Even the gold leaf ,
the leaf moves, so work is done,
as far as I know, that means electrons have flowed, qed current !

 

Consider the following. When you are driving down the road your car battery is moving with respect to the ground. Someone who is observing your motion who is stationary will consider the battery moving. The battery being two poles, one with a lack of electrons and the other with an excess of electrons. Now you have two opposite charges moving. Is that not a current? An even stranger case: Take a battery and place the positive terminal on an axis of rotation so that the positive terminal is stationary and the negative terminal is rotating about the positive terminal. This will generate a changing magnetic field that will in turn create a changing electric field and thus be emanating EM waves! Somehow the battery is losing energy simply be its rotation! Charge and current are intertwined.

 

Consider the following. When you are driving down the road your car battery is moving with respect to the ground. Someone who is observing your motion who is stationary will consider the battery moving. The battery being two poles, one with a lack of electrons and the other with an excess of electrons. Now you have two opposite charges moving. Is that not a current? An even stranger case: Take a battery and place the positive terminal on an axis of rotation so that the positive terminal is stationary and the negative terminal is rotating about the positive terminal. This will generate a changing magnetic field that will in turn create a changing electric field and thus be emanating EM waves! Somehow the battery is losing energy simply be its rotation! Charge and current are intertwined.

And if you modulate the rotation you can transmit music to a sensitive radio

 

OK we need to make a battery spinner and a long enough antenna to receive. We need to isolate the motor so it does not radiate.

 

I would like to take this one step further. Place the battery in orbit around the earth (or the sun it does not matter). Ballast it so that the positive terminal is 'stationary' and place it into a constant rotation along one axis. Because there is no friction, the rotation will continue indefinitely. But it must radiate EM waves and would not its rotations need to slow down due to the fact that energy is being lost? Would the battery be losing energy or would the rotation be slowing down?

 

Consider the following. When you are driving down the road your car battery is moving with respect to the ground. Someone who is observing your motion who is stationary will consider the battery moving. The battery being two poles, one with a lack of electrons and the other with an excess of electrons. Now you have two opposite charges moving. Is that not a current?

"Is that not a current" ?
I think that the commonly used definition for the phenomenon called "current" does not apply here.
I am sure that for the described case (movement of a charges of a battery) we do not yet have a suitable short technical term.
But, of course, you can think about whether it makes sense to expand the existing definition.

 

I would like to take this one step further. Place the battery in orbit around the earth (or the sun it does not matter). Ballast it so that the positive terminal is 'stationary' and place it into a constant rotation along one axis. Because there is no friction, the rotation will continue indefinitely. But it must radiate EM waves and would not its rotations need to slow down due to the fact that energy is being lost? Would the battery be losing energy or would the rotation be slowing down?

Well if it radiates energy then it is loosing mass and if it is loosing mass then the orbit would change. Less mass means wider orbit.

 

Consider the following. When you are driving down the road your car battery is moving with respect to the ground. Someone who is observing your motion who is stationary will consider the battery moving. The battery being two poles, one with a lack of electrons and the other with an excess of electrons. Now you have two opposite charges moving. Is that not a current? An even stranger case: Take a battery and place the positive terminal on an axis of rotation so that the positive terminal is stationary and the negative terminal is rotating about the positive terminal. This will generate a changing magnetic field that will in turn create a changing electric field and thus be emanating EM waves! Somehow the battery is losing energy simply be its rotation! Charge and current are intertwined.

Current is not electrical energy, current is a rate, a changing frame of reference in space and time.

With a "changing magnetic field that will in turn create a changing electric field" what is actually changing? Magnetic and electric fields are aspects of one relativistic object. The source of the magnetic field, B, is also a source of an electric field, E. There is no cause and effect, there is only a coupled existence. In the relativistic point of view, the “magnetic field” is just an electrical field as experienced by (i.e. relative to) forces on other charged particles in the vicinity. Frame of reference separates the electric field and “magnetic” fields for the observer.

For EM radiation on the spinning battery we need discontinuously distributed charge under acceleration. IMO what we will mainly see are non-radiating reactive fields (like a generators induction fields) with very little EM radiation with the energy source from the rotation of charge. Don't assume that just because there is this changing EM field, it has to transmit energy 'far' away from the charged body.

Initially stationary, uniformly accelerated for a short period of time, and then stopped accelerating.


The EM wave is the 'kink'

 

Ok. explain a pulsar next.