History in the Toolbox: The Vocabulary of Electrical Units

I am guessing that the average electrician doesn't realize how much history is knocking about in his or her toolbox. Volt, amp, ohm, watt—these electrical units are all eponyms, derived from the names of pioneers in the field. Let's have a tour.

Electricians measure electrical "pressure" in volts; that is, voltage is the "tension" in high-tension wires. The words volt and voltage come from Alessandro Volta, an 18th-century Italian scientist who made investigations in electricity and chemistry. He's best known as the inventor of the voltaic pile, more commonly known in English as the battery. Volta's pile was literally a stack—a pile—of zinc and copper disks separated by paper discs soaked in saltwater.

It was Benjamin Franklin who in 1748 suggested the term battery for this invention, in the sense of a collection of things used together, like a battery of artillery. (Speakers of other languages have a more direct connection to Volta's invention; the term for battery in French is pile, and in Spanish, pila.)

Volta's contemporary Luigi Galvani had discovered electricity in living creatures, which he did by making frogs' legs jump when he applied a shock. An early term for electricity generated by a voltaic pile was galvanism. Although we don't use that term any more, Galvani lives on in the word galvanometer, a device for measuring electrical flow. His name is also visible in the words galvanize in the sense of "to stimulate" (as if electrically shocked) and in the sense of putting an anti-corrosion layer on metal.

An amp (or ampere) is a measure of the quantity of electric current flowing through a wire. The term honors the French scientist André-Marie Ampère, who made discoveries about magnetism and electricity. Electrical current might flow easily through a substance (like metal) or it might encounter resistance. This resistance is measured in ohms, named for the German scientist Georg Ohm.

Electricians have need to measure each of these, and the original galvanometer evolved into the ammeter (from amps), voltmeter, and ohmmeter. These days, all of these measuring functions can be accomplished with a sigle device, and every electrician therefore has a multimeter in the toolbox.

I'm sure you recognize the term watt (for example, a 60-watt light bulb). Wattage indicates how much energy a device produces or consumes. This time it's the Scotsman James Watt, famous for his work with steam engines, who's remembered in the electrician's daily work. The connection is that watts measure a unit of work, like horsepower, which is an important factor in both steam engines and electrical devices. (In fact, 750 watts is equivalent to 1 horsepower.)

Even when we move from the electrician's toolbox to the electronics work bench or laboratory, we keep finding people's names. Coulomb, decibel, farad, gauss, hertz, joule, maxwell, oersted, siemens, tesla, and weber all refer to units related to electricity, and all invoke scientists who worked in the field. In a whimsical touch, names are sometimes inverted to indicate the reciprocal of a unit: a siemens (which has an -s even in the singular) is the reciprocal of an ohm, and an alternate term for the siemens is mho. Along those lines, a daraf has been proposed as the reciprocal of a farad, though that term has never been formally accepted.

Would you agree that this seems like an unusually dense collection of eponyms? It turns out that there's a tradition about this. And in a particularly satisfying bit of lexicography, we know exactly how it started. By the mid-19th century, although the electrical industry was expanding rapidly—by 1858 the first trans-Atlantic telegraph cable had already been laid—there were no standards even for the names of basic electrical units. In 1861, Josiah Latimer Clark and Charles Tilston Bright, two British electrical engineers, addressed themselves to this issue and presented their proposal for "universally received standards of electrical quantities and resistances" to the British Science Association. They published their ideas in a short article titled "Measurement of Electrical Quantities and Resistance" in the very first edition of The Electrician: A Journal of Telegraphy. Here's the bit that gets the ball rolling on our tour of famous names:

... let us derive terms from the names of some of our most eminent philosophers, neglecting for the all etymological rules.

They included this table of proposed unit names:

This is fascinating for a number of reasons. As I say, we don't always get such a precise view into the origins of terms. I'm intrigued by the authors' rejection of "etymological rules," which seems to me might mean either that they're eschewing Latin and Greek, or possibly that they're slightly altering the names for convenience.

It's also interesting because if you look carefully, you'll see that the terms that the authors propose are not actually the ones we use today. For example, they propose ohma for the unit of tension; we use volt today. And the reverse—they propose volt for resistance, whereas we use ohm today. You can also see that their suggestion to use galvat was not taken up, and we use amp today.

But it's clear that they started a trend, as the daily terminology of electrical units shows. In fact, it's hard to find a unit that isn't named for an "eminent philosopher."  Whatever discoveries are made in the future about electricity, I hope they keep up the tradition.