The Charge Paradox: A Historical Mistake That Shaped Electronics

I. Franklin Assigned Plus and Minus With a Guess, and Guessed Backwards #

In a wire, electrons are what actually moves, yet electrons carry a negative sign. The reason is not physics but a 50/50 guess Benjamin Franklin made in the 18th century, and the price of fixing it later.

Open a TV remote and you will often see two AA batteries, each with a (+) on its pointed tip. Physics class says current leaves from the positive end. Yet in the wire, the particles that actually move leave from the flat end marked (-).

Electric current is charged particles moving together in one direction. In a metal wire, they are electrons, tiny particles found in every atom.

On a schematic, the technical drawing of a circuit, the current arrow points from (+) to (-): the whole electronics industry draws it against the electrons. It all started with one man, one experiment, and a 50/50 guess made when nobody knew electrons existed.

In the mid-18th century, Benjamin Franklin proposed the single-fluid theory. It pictures electricity as an invisible fluid flowing from where there is more to where there is less. In fairness, I think it was a good model for its time. It explained why two objects rubbed together attract, and why touching them ends the effect. Rub a balloon on your hair and the hair rises after it: that is the same effect.

Franklin set the convention: an object with an excess of fluid is positive (+), one with a deficit is negative (-). Today we call the thing marked plus or minus electric charge: like signs repel, opposite signs attract.

The hard part was picking which object had the excess. Franklin rubbed a glass rod with silk. With no way to see individual particles, he went with intuition: the fluid moves from the silk to the glass, so glass is (+) and silk is (-). Two options, no way to check, 50% odds of being right.

Reality runs the other way. Rubbing moves electrons from the glass to the silk: the glass loses particles yet was labelled excess (+). The schematic arrow, which textbooks call conventional current, therefore follows Franklin’s imagined positive fluid, while the electrons in the wire go the other way. The guess was only slightly off: by exactly 180 degrees.

The electron itself would not be found for another 150 years.

II. In 1897, Thomson Found the Electron, and It Came Out Negative #

In 1897, J.J. Thomson found the electron using a cathode ray tube. It is a glass tube with most of the air pumped out and a piece of metal at each end wired to a power source. The bulky old CRT television was the same kind of tube, just bigger.

Switch it on and an invisible beam shoots from one end to the other, making the glass glow where it lands. Nobody knew for sure what the beam was. Thomson passed it between a positive and a negative metal plate to see which way it curved, and tried bending it with magnets too.

The result was clear:

• The beam was repelled by the negative (-) plate.
• The beam was attracted to the positive (+) plate.

Like signs repel, opposite signs attract: the particles in the beam can only be negative.

And that settled it. The electron, the particle that carries current in every metal wire, got the symbol of deficit (-). Not because it lacks anything, but because it arrived late, into a system labelled backwards a century and a half earlier.

The electron is the new hire handed a name badge printed before they showed up: wrong, but everyone already uses that name, so it stays on. So why has nobody reprinted it?

III. Why Nobody Fixed It Once It Was Known #

Reprinting sounds easy: give the electron the (+) and be done. The obstacle has a name: path dependence. It means an early choice, however arbitrary, becomes nearly impossible to change once millions of things are built on it. Not because it is right, but because fixing it costs too much.

The classic example is the QWERTY keyboard: a letter layout from the typewriter era, still on the phone in your hand. Current direction is a much heavier example.

By the early 20th century, Franklin’s convention was embedded in the entire industrial infrastructure. It sat inside Maxwell’s equations for electricity and magnetism, thousands of Edison and Tesla patents, every schematic, and every physics textbook on Earth. Flipping the electron’s sign meant rewriting all of it, down to the (+) on every battery, and every practicing engineer relearning the trade.

The second reason is what makes this tolerable: for circuit calculations, both descriptions give the same answer. A negative particle moving left produces exactly the same current as a positive particle moving right. Like an expense ledger: “spent 100,000 VND” and “received minus 100,000 VND” leave the same month-end balance, as long as the whole ledger uses one style.

So science took the pragmatic route: keep the convention, and separate two ideas cleanly.

• Conventional current: from (+) to (-), the standard way to draw schematics.
• Electron flow: the opposite direction, what physically happens in a metal wire.

Both are correct; they are two bookkeeping systems for one phenomenon. If this lived in a codebase, I would file it as a bug. The field closed that bug long ago as Won’t Fix: known to be backwards, deliberately left alone.

IV. How Electronics Lives With the Backwards Sign #

That split left a few entertaining consequences:

• The two batteries in your TV remote. Electrons gather at the flat (-) end. When the remote runs, they travel through its circuit from the (-) side to the pointed (+) tip. The (+) is a signpost for conventional current, not for the particles.

• Holes in every chip. Phone and computer chips are made of semiconductors. A semiconductor is a material like silicon whose ability to carry current can be tuned. Here physicists use a trick: instead of tracking a crowd of electrons inching left, they track the empty spot an electron just left, which drifts right. That spot is treated as a positively charged particle called a hole.

  It is like a bank queue: each time someone steps forward, the gap moves back one step. In a crowded line with one gap, following the gap is far easier, and that is the trick’s real payoff. The comparison breaks in one place: a gap in a queue carries nothing, while a hole counts as positive because it is missing an electron.

  A hole is not a real particle, but it behaves enough like one that every equation works, and it moves with conventional current. The entire semiconductor industry does its arithmetic on a particle that does not exist.

• Electricity in your body. The sharpest irony, and my favorite part, lands here. A nerve impulse is the electrical signal that travels along a nerve, and it runs not on electrons like copper wire but on sodium (Na⁺) and potassium (K⁺) ions crossing the cell membrane. An ion is an atom that has lost or gained electrons, so it carries a charge. Both of these ions have lost one electron, so they are genuinely positive.

  So in your body, these charge carriers really do move with conventional current, like Franklin’s imagined fluid. He guessed wrong about glass and silk, but his picture is right about his own nerves.

Next time you change the remote’s batteries, trust the (+); the electrons just go the other way. And a convention picked by a guess, once enough is built on it, lives on long after everyone knows it is backwards.