Does anyone know why there are these + - two symbols at the two ends of a power source?
Does it mean that one side has a deficiency and the other an excess of electrons?

The terminal with a + sign is at a higher potential than the terminal with the - sign.

 

Not necessarily so. Think of electric current as marbles in a tube.

View attachment 300808

Electricity is the motion of electrons along a conducting material. Electrons don't move very fast, about 2cm per hour. When one electron moves, another one follows behind to take its place. Hence, no, there is not an excess of electrons in one place and a deficiency in another.

They move because there is an electric field that pushes them along. The positive sign says that that part in the circuit is at a higher potential than the part with the negative sign. This is by convention. It is similar to why England is north of the equator and Australia is to the south. This is simply conventional.

What is an eclectic field not an excess and a deficiency of electrons?

 

What is an eclectic field not an excess and a deficiency of electrons?

No. You can create an electric field without involving charged particles.

 

It's all relative, too many or too few, whatever upsets the balance.

 

Not necessarily so. Think of electric current as marbles in a tube.

View attachment 300808

Electricity is the motion of electrons along a conducting material. Electrons don't move very fast, about 2cm per hour. When one electron moves, another one follows behind to take its place. Hence, no, there is not an excess of electrons in one place and a deficiency in another.

They move because there is an electric field that pushes them along. The positive sign says that that part in the circuit is at a higher potential than the part with the negative sign. This is by convention. It is similar to why England is north of the equator and Australia is to the south. This is simply conventional.

Hi,

Well, where does the electric field come from

 

If you delve into EM theory and Maxwell's Equations you will find that you do not need charge separation to create a field.
For example, eddy currents are created by changing magnetic fields in a solid conductor.

 

No. You can create an electric field without involving charged particles.
[/QUOTEReally?

For example, eddy currents are created by changing magnetic fields in a solid conductor.

And that doesn't involve the electron, which is a charged particle?

 

What is an eclectic field not an excess and a deficiency of electrons?

Electric fields can be caused by net unbalanced charges and

Time-varying magnetic fields can produce electric fields (and time-varying magnetic fields can produce electric fields) that are really just transformations of a single entity called the EM force.

 

Exactly, it is not charge separation that creates the electric field in a generator, it is the changing magnetic field.

Getting back to the original question, the terminal are labelled + and - so you don’t have to guess which way to hook things up and have a 50% chance of destroying electronic devices.

 

it is not charge separation that creates the electric field in a generator, it is the changing magnetic field.

And that changing magnetic field is generated by a moving electric field.
A magnetic field can be viewed as the Relativistic effect of a moving electric field due to moving charged particles.
You can't have a magnetic field without involving charged particles (usually electrons).

 

If you delve into EM theory and Maxwell's Equations you will find that you do not need charge separation to create a field.
For example, eddy currents are created by changing magnetic fields in a solid conductor.

Hi again,

Oh yes, I was referring to the static case like a battery with no current flowing.

 

And that changing magnetic field is generated by a moving electric field.
A magnetic field can be viewed as the Relativistic effect of a moving electric field due to moving charged particles.
You can't have a magnetic field without involving charged particles (usually electrons).

Only in the trivial sense that it contains atoms with protons and neutrons. There is no net movement of charge in a spinning magnet used in a generator.

 

Only in the trivial sense that it contains atoms with protons and neutrons. There is no net movement of charge in a spinning magnet used in a generator.

In that case the movement is in the electrons around the atoms in the magnetic material that are lined up to produce the magnetic field.
How else do you think a magnet generates a magnetic field?

 

As R. Feynman once said magnets are complicated.

The magnetic field from the magnet used in a generator is based on the Quantum Property of 'Spin (something with no classical analogy). The atoms in the magnet are electrical neutral as the electrons don't actually spin,, instead we have magnetic movements due to the interaction of QM spin and charge.
https://quantumphysicslady.org/glossary/spin/

One experimental result with electrons, in particular, is striking. Maxwell’s Laws of Electromagnetism tell us that a moving electrical charge creates a magnetic field. For example, electricity, that is, a stream of electrons flowing through a wire, creates a magnetic field around the wire. As an electron was found to generate a magnetic field around itself, physicists postulated that it’s moving and, possibly, spinning. However, their calculations soon showed that the electron could not possibly be spinning. But, the name for the magnetic quantum property, “spin,” stuck.

https://quantumphysicslady.org/glossary/magnetic-moment/

A note about spin: As a note, physicists don’t visualize quantum particle spin as a rotational motion. In fact, physicists provide no visualization for spin at all. While initially, physicists assumed quantum particles were spinning like a top, their calculations soon showed that this would be a physical impossibility. They simply define “spin” as that property, which, in the presence of the quantum particle’s electrical charge, gives it a magnetic field.

 

In that case the movement is in the electrons around the atoms in the magnetic material that are lined up to produce the magnetic field.

How quaint, you must have missed the last 100 years of physics.

 

Be nice. Your sarcasm was unwarranted and not needed.

 

How quaint, you must have missed the last 100 years of physics.

You sarcasm is appreciated, as I now know what kind of R.O. you are.

 

In that case the movement is in the electrons around the atoms in the magnetic material that are lined up to produce the magnetic field.
How else do you think a magnet generates a magnetic field?

How quaint, you must have missed the last 100 years of physics.

Hi there Bob,

Why don't you simply explain your position on this, that's the only way to convey information. Maybe you have an important thought, but it gets wasted if you don't articulate it to others.

Thoughts from somewhere on the web...
"A magnetic domain is a region within a magnetic material in which the magnetization is in a uniform direction. This means that the individual magnetic moments
of the atoms are aligned with one another, and they point in the same direction. "

 

Why don't you simply explain your position on this, that's the only way to convey information. Maybe you have an important thought, but it gets wasted if you don't articulate it to others.

Check out the post immediately preceding mine. Richard Feynman can do a better job explaining than I do. The crux of it is is that the theory of an atom in which the electrons orbit the nucleus was superseded by QM about 100 years ago.

 

Check out the post immediately preceding mine. Richard Feynman can do a better job explaining than I do. The crux of it is is that the theory of an atom in which the electrons orbit the nucleus was superseded by QM about 100 years ago.

It's sort of unfortunate (but not uncommon) that original idea names (spin, orbits, movements, etc..) and conventions (electrons flow vs conventional current) are preserved because of historical usage from 100+ years ago. Even experts like Richard Feynman sometimes are/were exasperated when questions and responses require some understanding of the history of terms and common ideas that are currently obsolete but a still in common usage because of the need to explain, something, somehow.