Behind the Dictionary

Lexicographers Talk About Language

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.


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Mike Pope has been a technical writer and editor for nearly 30 years. He has worked at several software companies, including Microsoft, and currently works in Amazon's cloud computing division. You can read more at Mike's Web Log and Evolving English II. Click here to read more articles by Mike Pope.

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Comments from our users:

Wednesday May 21st, 5:41 AM
Comment by: Juan Jose Hartlohner (Madrid Spain)
Horsepower (hp)
During my pilot training in Florida, one student asked the instructor the meaning of "horsepower". I volunteered that it was a unit to compare the output of a steam engine with the power of draft horses, namely 75 kilograms-meters per second. After consulting, the instructor confirmed it to be 550 foot-lbs per second.
In many languages hp is translated as cv, c for horse and v for vapor (steam).
The metric horsepower is equivalent to 735.5 watts.
For electrical power, one hp equals 746 watts.
Wednesday May 21st, 7:44 AM
Comment by: Jeff H. (Ann Arbor, MI)
In the table of units, the larger unit labels are not what are used today. Milli- became Mega, and Billi- became Giga. Verbally, people don't say killi-ohms, etc. They would be understood, but it's more common to say K-ohms. But people do say megaohms and gigavolts.

Another possibly interesting point. In electrical engineering, the suffixes K, M, G (for killi-, mega-, and giga-) represent powers of 10, ie 1,000, 1,000,000, and 1,000,000,000). But in computer science those suffixes represent powers of 2, ie 2^10=1024, 2^20=1,048,576, and 2^30=1,073,741,824. These latter units are what are used to specify sizes of memory in computers, as well as hard drives, USB thumb drives, etc.

So, for example, a megaohm is 1,000,000 ohms, but a megabyte is 1,048,576 bytes.
Wednesday May 21st, 8:38 AM
Comment by: Orin Hargraves (CO)Visual Thesaurus Contributor
Great article, Mike. I'm reminded of hemorrhoid jokes that naturally come to the minds of bent English speakers when traveling in Francophone countries where there are advertisements for "piles."
Wednesday May 21st, 12:35 PM
Comment by: Amy R. (Denver, CO)
Nice article, but I cringed a bit on the definition of a Watt. Watts measure energy expended per second. (Power) One Watt is a Joule per second. Joule named after James Prescott Joule of course.
Physicists use eponyms all the time. Force measured in Newtons, magnetic field measured in Teslas, energy in Joules, etc. But it's very important to keep the definitions straight, since the definition refers us to the equation. The units have to come out right in the end, or there's an error somewhere.
Wednesday May 21st, 11:06 PM
Comment by: Mike P. (Seattle, WA)Visual Thesaurus Contributor
@Juan -- thanks for the details. I was not aware that there are different abbreviations for HP in different languages! It makes sense etymologically, of course.

@Jeff -- excellent observation about the difference in what we mean today by milli-/billi- (well, millio- and billio-, as they have it). It had occurred to me when looking at the table originally that Clark and Tilston were advocating a decimal-based system. I didn't point it out in the article since it wasn't germane to the issue of naming, but now it makes we want to do a little research about how early the metric system was adopted for international science and engineering.

It's also a good point about the difference between computer K's and metric K's (so to speak). In practice, it doesn't seem to lead to much confusion, since the context (hence unit definitions) tends to make things clear.

@Amy -- I'm sorry to make you cringe. I deliberately did not get into technical definitions of the different units, since the focus is specifically on the eponymous nature of all these units. Is it incorrect to say that a watt is a unit of work? If so, I don't think the definition is actually wrong, just ... general. (I might have gotten that phrase from Vocabulary.com: http://www.vocabulary.com/dictionary/watt.) I did note "joule" and "tesla" in my "also named for people" list. I didn't include newtons, probably, as I now think back on it, because that struck me as pretty far away from all things electrical. But it's a fair point.

@Orin -- :-)
Thursday May 22nd, 1:06 AM
Comment by: Amy R. (Denver, CO)
No, a Watt is not a unit of work. Work is a force expended over a distance (think of picking up a box) Work is a form of energy and is measured in Joules. A Watt is a Joule per second a unit of power (think of picking up a box either quickly or slowly. Quickly is high power, slowly is low). I think that students (and others) are confused because power, work and energy are used interchangably in common usage but are specifically different concepts in physics.

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