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I don't understand how can a for example a battery be positive charged when the electrons are negative charged? I've read that protons are positive but they can't move so are all electricity negative?

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    \$\begingroup\$ what do you mean by positive charged? .... what do you mean by all electricity? ... are you talking about electric current? \$\endgroup\$
    – jsotola
    Sep 5, 2019 at 19:52
  • \$\begingroup\$ (I love how a simple question can turn into heated discussions.) To the OP: You should buy a copy of, 3rd edition or later, "Matter & Interactions" by Bruce Sherwood and Ruth Chabay. Very well presented physics related to electronics. \$\endgroup\$
    – jonk
    Sep 5, 2019 at 20:22
  • \$\begingroup\$ As a philosopher, Ben Franklin understood the "direction" did not matter; the thinking and experimenting proceeded ahead. \$\endgroup\$ Sep 6, 2019 at 2:15
  • \$\begingroup\$ @analogsystemsrf I'm glad he wasn't designing airplanes or firearms! \$\endgroup\$
    – DKNguyen
    Sep 6, 2019 at 20:52

6 Answers 6

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First before answering what I think is truly your question, I will have to beat into you how voltage are relative:

An atom has protons in the nucleus which is orbited by electrons. If the numbers are equal, then the positive and negative charges cancel out and the charge is zero.

Suppose we start with two terminals. Each terminal has a net charge of zero there are the same number of orbiting electrons as there are protons in the nucleus at both terminals). That also means neither terminal is positive or negative relative to each other.

If you rip some electrons off the atoms in one terminal and shove them into orbits around the atoms in the other terminal, then the terminal that lost electrons becomes more positive and the terminal that gained electrons becomes more negative relative to each other.

So the positive charge is due to protons and the negative charge is due to electrons, BUT what is important is that you understand that the protons DO NOT MOVE, not independently of the nucleus anyways (that would be a nuclear reaction). You do not produce a positive charge by moving protons around

You produce both positive and negative charges by moving electrons around to mess with the imbalance of electrons and protons. As a result, it is often more useful to think about a positive charge as a deficiency of electrons rather than an excess of protons since you are manipulating electrons, not protons.

NOTE: Some people have pointed that hydrogen ions, basically just the nucleus of hydrogen which is just a proton, can move around just fine and carry a positive everywhere they go. They can, but the difference here is that the proton was already free. It was not ripped from a nucleus and then relocated in order to move a positive charge from place to another. That ripping action is a nuclear reaction.

If you had three different terminals:

  1. One with a balance of protons and electrons
  2. One with fewer electrons than protons.
  3. One with more electrons than protons.

Then #2 would still be more positive than #1, and #3 would still be more negative than #1, even though #1 doesn't have an excess of anything (net charge of zero). It's all relative.

That means that if you had three terminals:

A. One with a balance of protons and electrons

B. One with more electrons than protons

C. One with even more electrons than protons.

Then B would be positive relative to C, but negative relative to A. It's all relative. Whether something is positive or negative is entirely dependent on what you are measuring it with respect to.

The voltage of something relative to itself is always zero, because it's like measuring sea-level with respect to sea-level. It doesn't matter what sea level ends up being, it is always equal to itself so the measurement relative to itself is always zero.

Now, to address your actual question: We don't say electricity is positive. We also don't say a battery is positively charged. Don't forget a battery has both a positive AND a negative terminal, and everything is relative.

What is more likely to be happening is that the ground/0V in your circuit was chosen as the point of reference against which all other voltages were measured. Then the negative terminal of the battery was connected to this point, and people don't always want to say "relative to ground" all the time, so they just say the battery is positive. It's completely possible to have a second battery in the circuit where the positive terminal is connected to ground to provide a negative power supply.

When analyzing most circuits we tend to follow the current flow as if electricity is positive charges moving when in reality is is electrons (which have a negative charge) that are flowing.

This is because early scientists assumed the charge carrier was positive early on and by the time they figured out their mistake it was too entrenched and would take too much work to fix so it stuck. It doesn't matter for most circuits because most circuits have electrons moving through a sea of nucleui that have protons present so it is mathematically equivalent that a positive charge moves in the opposite direction of the negative charge.

But it matters in some things where this mathematically equivalency is not the case such as vacuum tubes and semiconductor physics where it actually does matter that a negative charge is moving.

For example in a wire, you have those copper nuclei containing protons providing that positive charge whenever there is no electron to balance it out to produce a net charge of zero. So mathematically, electrons move in the opposite direction of the positive charge produced by "absence of the electron". It is the "absence of the electron" that moves in the opposite direction of the electron (not the proton because the proton doesn't move.) But in a vacuum tube you have a vacuum. There are no or nuclei or protons in that vacuum. When an electron moves away, there is no proton left behind to produce a net positive charge. You literally have a negative charge carrier (the electron) moving through the vacuum.

It's dumb. I hate it.

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    \$\begingroup\$ You are seriously confusing the density of charge carriers with their energy (voltage). In your "three terminal" example, the positive and negative terminals are charge neutral but the energy level of the charge carriers is different. Protons and other positively charged atomic nuclei can indeed move. For example, alpha particles that caused upsets in early DRAMs. Or fuel cells. \$\endgroup\$ Sep 5, 2019 at 19:43
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    \$\begingroup\$ Charge is not a relative value like voltage. Charge is an absolute quantity and it is measured in coulombs. The amount of charge represented by a coulomb is equivalent to a specific, exact number of electrons. \$\endgroup\$ Sep 5, 2019 at 19:44
  • \$\begingroup\$ @ElliotAlderson I'm trying to keep it in a way that the OP understands. This is already probably an information dump to him as it stands. \$\endgroup\$
    – DKNguyen
    Sep 5, 2019 at 19:44
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    \$\begingroup\$ But you are describing things that are completely false. I think you just make matters worse. \$\endgroup\$ Sep 5, 2019 at 19:45
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    \$\begingroup\$ @ElliotAlderson I removed some direct references to charge being relative, but it probably won't satisfy you since charge is still used an awful lot to refer to the voltage produced when individual electrons are moved around. \$\endgroup\$
    – DKNguyen
    Sep 5, 2019 at 19:55
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Current flow as ‘positive’ to ‘negative’ is a convention that predates charged particle theory. Blame Ben Franklin, for one: https://whyy.org/articles/does-our-confusing-electrical-nomenclature-start-with-ben-franklins-theory/

Some 150 years after Franklin when electron theory came about (JJ Thomson and others), this made things confusing, as clearly the mechanism of charge transfer was shown to be the movement of electrons. Even later, with semiconductor theory we invented concepts like ‘hole flow’ to patch this over.

Still, it’s singularly unsatisfying to have to flip back and forth between thinking about electron flow and current flow. Analyzing the function of batteries, vacuum tubes, solar cells, electrochemical reactions, semiconductors and high-voltage generators all rely on an understanding of electron flow. Yet the notion of conventional current flow from positive charge to negative charge persists.

Fear not. As long as you are consistent and have the signs right, the math works out.

BONUS: xkcd (thanks @JonRB)

enter image description here

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    \$\begingroup\$ obligatory XKCD xkcd.com/567 \$\endgroup\$
    – user16222
    Sep 5, 2019 at 21:40
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    \$\begingroup\$ I think this does not really answer the question. If electric charge of electrons would have been defined positive OP could still ask "How can electricity be negative when electrons are postive?". Also: holes are not an invention to fix that unlucky historical definition. They are needed especially to explain semiconductor physics. And also there a different definition of the sign of the elementary charge whould not help to avoide the concept of holes (which is not a bad or unfortunate concept at all) . \$\endgroup\$
    – Curd
    Sep 6, 2019 at 8:36
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    \$\begingroup\$ @Curd "OP could still ask "How can electricity be negative when electrons are postive?".: Well, only if electricity was still commonly interpreted as flowing in the opposite of direction of the electrons...which I somehow doubt would be the case if electrons were defined as having a positive charge. Although it would muck other things up since the more efficient (therefore common) N-type semiconductor devices would now no longer have their source pin be the same as the reference node in many circuits. It would make the ideal high-side switch in both simplicity and efficiency an NMOS though. \$\endgroup\$
    – DKNguyen
    Sep 6, 2019 at 16:23
  • \$\begingroup\$ @DKNguyen: I mean even if the elementary charge (of electrons) was defined positive and common electric current was defined to be in the same direction as electrons flow still there would be postive and a negative terminals at batteries. Still bodies could be charged positive or negative and still OP could ask.... \$\endgroup\$
    – Curd
    Sep 6, 2019 at 18:09
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Power generated is -ve polarity, regardless of voltage polarity DC or AC.

Load power is +ve dissipated power by definition.

Flow of current is from V+ to V- by IEEE convention, regardless that the flow of electrons is in opposite direction. This serves more logical analysis with KVL, KCL and thus all meters indicate this current polarity. The detailed reasons do not matter.

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    \$\begingroup\$ Hey, don't let Ben Franklin off the hook for this "conventional current vs. electron flow" issue. I'm in 'Murica and I blame him every chance I get. :) \$\endgroup\$ Sep 5, 2019 at 21:36
  • \$\begingroup\$ @ElliotAlderson I thought it went back to Volta and the first batteries - a 50/50 chance and it was the wrong way round... but as lng as we all use the same system then it works... \$\endgroup\$
    – Solar Mike
    Sep 5, 2019 at 21:47
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  • Battery is usually not positively charged. It is charged (there is a voltage difference between its terminals) or discharge (no voltage between terminals). If it is positively charged, that means connecting it to the ground using one conductor results in a short current flow through the conductor. Any object can do that.
  • Protons can move. Protons (particles building atom cores, nuclei) cannot move only in solids, in liquids, gases and plasmas they are free to move.
  • Most of the electrons are bonded to the nuclei and in solids they cannot move either. Only small part of them are free to move.
  • Electricity is neither positive, neither negative. Electricity is a common word covering "thingies that have something to do with electrons". It's like magnetism, genetics, universe...

Atom/molecule is electrically neutral. That means within its volume the net count of protons equals the count of electrons. Ion/molecullar ion is charged. That means that the net counts of protons and electrons does not match. Cation is ion with proton count higher than electon count, Anion has lower proton count than electron count.

In other words, you can consider positive charge as a lack of electrons and negative charge as electron surplus.

What is responsible for the current flow
In metals the particles that carry the charge are electrons that are free to move while all protons and most of the electrons are locked in their position by metallic bond.

In semiconductors, the particles that carry the charge are free electrons (dominant way in n-type semiconductors) and electrons that relocates from one atom's cloud to the "hole" in the other's (dominant way in p-type semiconductors). When observed from distance, in n-type semiconductors in seems that free negatively-charged electrons are moving, in p-type semiconductors it seem that the positively-charged "holes" are moving.

In ideal insulators, no charge is moving at all.

In liquids - aqueous salt solutions or molten salts to be more precise - both charged particles, cations and anions, are free to move so they both contribute to overall current. Part of the particle flow has the same direction as the current, the other part flows in direct opposition. Pure water (demineralised, deionised) does not conduct.

Gases are considered insulators.

Ionised gases, that can conduct, are called plasma and both free electron and ions contribute to the net current in such medium.

Battery charge
Battery considered charged is not charged at all. Here, the limitted vocabulary plays dirty pun on many people.

I've mentioned one meaning in the very beginning - (net) charge is a difference between proton count and electron count within given volume - here the battery.

The other meaning of being charged is that when two terminals are connected, the current flows from one to the other. As the first unit of meter was defined as "this log is one meter long", it was defined that (back then abstract) positive charge flows from terminal labelled + to terminal labelled -.

Battery being charged means that its net charge is zero while one part is electron-rich and the other is electron-scarce. Both parts assessed individually are thus charged. The battery inner structure prevents the charge to equalize internally so the only way, how to equalize the charge - discharge - is through outer circuit.

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It's historical. The thought was that in a battery something had to flow from the more precious, valuable metal to the less precious metal. Of course that doesn't exactly explain why it's the less precious metal that is corroding.

It turns out that to a large degree it doesn't matter whether charge is transported by positive or negative or imaginary particles with regard to circuit design. For vacuum tubes however, this becomes very important for designing the internals (you need to heat the cathode to let it emit electrons easily). Semiconductors are already more ambivalent (you can to some degree swap p and n though electron holes tend to have larger mobility than electrons). For resistors and even capacitors and solenoids, it's not all that relevant. The chemistry of electrolytic capacitors needs to be done right, of course.

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You are correct that electrons are negative, and protons are positive. You are also correct that only electrons can flow through a conductor, while protons can't. So, what happens when all the electrons flow away from a region, leaving the protons behind?

That's the way chemical batteries work. A reaction internal to the battery strips electrons from the positive terminal, concentrating them at the negative one. Thus, the positive terminal winds up with more protons than electrons, while the negative terminal has more electrons than protons.

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  • \$\begingroup\$ electricity includes ion flow, which can certainly be positive. There's a lot more to current that what happens in a copper wire \$\endgroup\$ Sep 6, 2019 at 16:14
  • \$\begingroup\$ Ions can flow when they're in a gas or liquid, but in a solid copper wire, ions can't flow in any meaningful way. \$\endgroup\$ Sep 7, 2019 at 2:47

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