# Electric potential and the flow of electrons in a battery

I started reading about electricity a few days ago and there are some things that confuse me. What I want to ask about here is the apparent contradiction in two facts that I have read, they are:

1. Electrons flow from the negative end of a battery to the positive end.
2. Electrons flow from higher electric potential to lower electric potential.

The negative end of a battery is supposed to be "ground" which is the reference point to measure voltage from. The negative end is defined as being 0 volts while the positive end is 9 volts (if we use a 9V battery as an example). So then why do electrons flow from the low volt end to the high volt end, shouldn't it be the other way around given fact number 2 listed above?

I may very well have misunderstood something and made factual errors in my claims above, but just a week ago I knew pretty much nothing about how electricity works, so please forgive me.

The problem that there is actually an ambiguity with the definitions. So:

1) There is a conventional current flow direction that is defined as the flow from the higher potential to the low. It was defined a while ago, upon the discovery of the electricity. And it was defined incorrectly, but we still use it.

2) There is an electron flow. It is going from low potential to the high one thus opposite to the conventional flow.

So.. We have to live with that or...

(Copyright notice: The image is taken from the XKCD.com comics site)

• RE "it was defined incorrectly". There's nothing incorrect about it. The definition is arbitrary. Electrons are not the only carriers of charge, and not all currents are flows of electrons. – The Photon Jul 28 '15 at 19:31
• @ThePhoton But it was actually believed that it is the direction of electron flow. – Eugene Sh. Jul 28 '15 at 19:33
• So the second point on my list is in reality just flat out wrong and it should be the other way around? I feel like I need to confirm this. – Just some guy Jul 28 '15 at 21:06
• @Justsomeguy You have two bullets contradicting each other, so yes, one of them would be always wrong :) – Eugene Sh. Jul 28 '15 at 21:08

The electrons are confusing and you should ignore them.

Conventional current flows from positive voltage to negative voltage.

Electrons are negatively charged and attracted to positive objects: they will flow "up" an electric field towards the positive voltage.

The reason you should ignore the electrons is not only are they going the wrong way, but not all electric current is carried by electrons. Current flows through a capacitor without a flow between the plates. Current flows in ionic solutions (such as inside battery electrolytes) through the movement of ions. Current flows in semiconductors in the form of "holes", the absence of an electron.

First, be sure you're clear about whether you're talking about the current flowing through the battery, or the current flowing through the rest of the circuit due to the potential generated by the battery.

I'll assume you're talking about the current through the rest of the circuit, not the current through the battery.

Electrons flow from the negative end of a battery to the positive end.

This is correct.

Electrons flow from higher electric potential to lower electric potential.

This is not correct. Electrons have a negative charge. So when they are in an electric field, the force on the electron is in the opposite direction from the direction of the field.

A battery creates a positive potential on the "positive end" relative to the "negative end". That means there is a field pointing generally from the positive terminal to the negative terminal. So electrons will flow from the negative terminal to the positive terminal (like in your first statement).

Because the electrons have negative charge, when the electrons flow one way, it means the conventional current is flowing the other way. So what you should have been told is

Current flows (in the rest of the circuit) from the higher electric potential to the lower electric potential.

Again, there must be a closed circuit, so within the battery chemical energy is actually being converted to electrical energy to cause a current to flow from the negative terminal to the positive one.

Energy is what flows in a circuit. (Not the common English language meaning of the word, but a very precise definition used in physics.) Energy is the potential to cause something to change or something to happen.

Electrons are quantum-mechanical artifacts that don't really matter unless you are trying to understand semiconductor devices (diodes, BJT transistors, FETs). Sometimes we imagine electrons as little balls of charge that orbit around the outside of an atom -- but that's a simplified model that is misleading when trying to understand how electronics works. At those very small scales, the world doesn't work the same way as we're used to; electrons and photons are not so much solid particles so much as they are waves that often behave similar to particles. Their actual location and momentum are never precisely known -- that's why electrons are described as having "orbitals", a broad set of locations where the electron is likely to be.

Electron Migration is what happens when an electron drifts from one location (orbital) to a nearby location (another orbital). Again, the reality of quantum mechanics makes it harder to explain, but if you think of electrons as little balls of charge, when they drift from orbiting one atom to orbiting a nearby atom, that's electron migration.

Electric Current Flow is what happens when energy is transferred by a bunch of electrons, passing the energy from one to another, like a bucket brigade. Packets of energy are passed from one electron to the next electron in turn.

If you think of fans in a sport stadium performing "the wave", where the people in row 1 raise and lower their arms, and then the people in the next row raise and lower their arms, and so on -- it looks like a wave of arms racing across the stands, even though most of the people are still in the same place. In this analogy, the electrons are like the people, able to migrate (slowly) from one seat to a nearby empty seat, but the "wave" is the actual energy being propagated through the circuit.

Another electric current flow analogy is a bicycle chain, transferring energy from the pedals to the rear wheel. The chain forms a complete circuit, with the top links of the chain in tension as the pedals' gear pulls the rear wheel gear, and the lower links are slack as they form a "return current" back to the source of energy. (This analogy only works for a single mesh, real electronic circuits can have multiple meshes -- and a bicycle chain can't split and merge like a flow of electric current does.) (Remember, this is energy that's flowing, not electrons.)

Often you will hear about the "water analogy", which tries to explain the relationship between potential (voltage) current (flow) and resistance. This is a flawed analogy because it leaves one wondering if there is a pile of electrons accumulating at the end of a light bulb... in fact there always must be a return current, and the electrons themselves don't migrate out of the wires onto the floor. Just like the fans in the stadium, the wave can't propagate out of the stand into an area where there aren't any people. Similarly the electric current can't flow outside of an electric conductor.

All of these analogies are incomplete; nothing else behaves exactly like electricity. Our best and brightest minds struggled with this for hundreds of years to get where we are today. So don't worry if it seems abstract and hard to understand; it really is. Keep with it and it will start to make sense eventually.