Does electrical current flow from positive to negative or negative to positive?

Question

When you listen to people wiring up a DC circuit they seem to mumble about the electricity flowing from positive to negative. However in school I was always taught that DC electricity flowed from negative to positive.

I was googling for this and didn't see the definitive Stack Exchange post. Anything I read either isn't clear about this or is too complicated for me to understand.

Can someone please explain this to me like I'm 5? It seems like one of those things where both sides are right but there is a subtle difference that is difficult to communicate.

Answer 1

The answers you were given and what you were taught in school are all correct. When electric current was first discovered people didn't know which way to choose and they assumed that it flows from positive to negative. Later it was proved that it is the other way, electrons seeking the positive terminal. Despite this new discovery, nobody wanted to change the way of looking at this flow, so it's still considered to be from + to - for two reasons:
-The same calculations, laws and formulas work for both ways
-There were already many books and documents based on this concept and everyone was already used to it. Since it wouldn't affect the computations and the rest, there was no need to change it.

Answer 2

In the beginning, before anybody knew about electrons, Benjamin Franklin postulated (guessed) that "electricity", whatever it was, moved from the arbitrarily named positive pole of a battery to the negative, in order to do its work.

We now know better, and when it matters it's taken into account.

For most work it doesn't matter, so his convention is still followed, and charge flowing from positive to negative is called "conventional current".

Answer 3

First, we have some issues with the terminology. "Electricity" is not really all that well defined term. I'm not aware of any measurement units that measure electricity or anything like that, so I'll just avoid talking about it.

Instead, I'll talk a little bit about physical quantities we know. The interesting ones here are electrical current, electrical charge and electrical potential.

Current is defined by amount of electrical charge that goes through some surface in a unit of time.

So let's take a look at this image here:

The black shape is some material through which electrical charge can somehow flow. The red disk is the surface through which the charge is flowing. This is our "counter". So when we say that we have current of X amperes, that means that we have flow of one coulomb of charge through the surface in one second. So far so good.

Now comes the part with the "electron flow" and the "conventional current" flow. You have to keep in mind, back then when our first scientists were researching electrical current intensity, it wasn't all that well known what this current thing is and what it's made of. People didn't know that it was electrons that carry the charge. They did know that it was something there, but what exactly it was, that wasn't very clear.

So what they did was simple: They studied the macroscopic model. That was the practical thing to do. If you want to use a battery, you don't really need to know how many electrons can go from one side to another. It's good if you do, but that's not practical knowledge. Instead, it would be much better to know that it can supply say 3 amperes for two hours until discharged.

There was also the development of notion of "electrical potential". It was logical to imagine that our current will flow from places of higher potential into places of lower potential, so that's how we defined the direction of current flow.

When the two potentials even out, the current flow stops.

So over time, circles of people involved with electricity took a standardized direction for the movement of current and continued to develop other useful things from that. In parallel, you had the people who were researching the microscopic world. Over time, they managed to figure out that you had carriers of electrical charge and that in metals, they are usually electrons. They also realized that say in liquid solutions, you can have ions that can carry current as well. Over time, it turned out that the flow of electrons is opposite of what the macroscopic guys who were working with current defined to be the positive direction of current and that's how we got the "electron" current (blue in picture) and the "conventional" current (black in picture).

As previously said, the macroscopic world worked up to a level without actually understanding what's going on at the low level. The result was that the discovery of the sign of charge of electrons made no significant impact on the workings of things in the big picture of electricity. So there was no pressing need to redefine the direction of current flow in traditional electrical engineering. It just turned out that our electrons move in the opposite direction of what we thought they do, but everything else is the same. So it remained that the conventional current flows from the location of higher electrical potential to the location of lower electrical potential, but actual flow of electrons is in the opposite direction. So both are actually correct.

Answer 4

Does electrical current flow from positive to negative or negative to positive?

The answer to that question depends on:

1. Whether we're considering the actual flow of charges, or the hypothetical flow of positive charges in metallic conductors that is known as conventional current. When in a metallic conductor, at some instant of time, the actual negative charges (electron current) are flowing in a particular direction, the hypothetical positive charges (conventional current) are flowing at the same rate but opposite direction.

2. The device we're considering.

3. The instant of time we're considering.

Here are some examples:

• In a resistor, an incandescent light bulb, a heater and a rectifier diode, the hypothetical positive charges (conventional current) always flow from a higher (or +) to a lower (or -) electric potential.
• In an inductor and capacitor that are carrying a sinusoidal flow of hypothetical positive charges, and have a sinusoidal voltage across them, the answer still depends on the instant of time under consideration; when those devices are storing energy, the hypothetical positive charges are flowing from a higher (or +) to a lower (or -) electric potential; but when those devices are releasing energy, the hypothetical positive charges are flowing from a lower (or -) to a higher (or +) electric potential.

Note that a common misconception is to think that conventional current flows from positive to negative. That's not always true. That's always true in resistors, but not in inductors and capacitors (for example).

As an example, consider a circuit consisting of a resistor in series with an inductor, and a sinusoidal voltage source applied across the series combination of those two devices. After some time, the current through the circuit will also be sinusoidal (of same frequency as the applied voltage). So this an AC circuit, not a DC circuit. The circuit is shown here (the image size is too big to upload in this website, 3.78 MB). We can divide one cycle into four time intervals:

• 1st mode of operation: When the voltage is positive and the conventional current is negative. In this case, the inductor releases energy. The conventional current flows from a lower/- to a higher/+ potential (node c to node b).

• 2nd mode of operation: When the voltage is positive and the conventional current is positive. In this case, the inductor stores energy. The conventional current flows from a higher/+ to a lower/- potential (node b to node c).

• 3rd mode of operation: When the voltage is negative and the conventional current is positive. In this case, the inductor releases energy. The conventional current flows from a lower/- to a higher/+ potential (node b to node c).

• 4th mode of operation: When the voltage is negative and the conventional current is positive. In this case, the inductor stores energy. The conventional current flows from a higher/+ to a lower/- potential (node c to node b).

Answer 5

Electricity is transition (moving) of electrons. So, What you was taught in school is right.

When an electron leaves its place, a net positive charge appears due to the positively charged protons which remain. So, If many electrons flow in a specific direction, You can consider or imagine that there are virtual positive charges flow in the opposite direction.

For example: If you have some electrons placed at node "A" and the electrons moved to node "B". First, Node "A" had less positive charges than node "B". After moving the electrons, Node "A" become more positive than node "B". So we can say that the positive charges have moved from node "B" to node "A" (the Opposite direction of electron flow).

Answer 6

Electrons move to create electricity. However, quantum physics makes the answer weird. Holes (the absence of an electron) yield positive charge and they behave no different from real particles, like electrons. This feature of reality is known as a quasiparticle

In a metallic crystal, like a typical metal wire for circuitry, electrons are not seen moving from atom to atom. There is a superposition of states that resembles a charge cloud. In this cloud, positive and negative charge statistically build at interface points and that's about all you really measure of what's happening inside the circuit's segments.

It's more complicated than the above description, but the point is that it truly makes no difference which way you think about it. Arc welders do care, but they are very interested in two important interface points, so they're an exception.