I refurbish old tube type radios. I know when I was a child, my father referred to capacitors as condensors (condenser?). I see references to condenser in old manuals and parts lists. I know terminology does change, such as using Hertz rather than "cycles per second" (cps) as reference to frequency.

Does the word condenser have a basis in understanding capacitance?

What was condensed? There must have been reason to use the terminology.

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    \$\begingroup\$ Speaking of strange units, I am personally quite fond of kmc. Yes, that is 'kilo mega cycles', or GHz in modern terminology. \$\endgroup\$ Commented Mar 11, 2016 at 23:25
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    \$\begingroup\$ According to Wikipedia: "Early capacitors were also known as condensers, a term that is still occasionally used today, particularly in high power applications, like automotive systems. The term was first used for this purpose by Alessandro Volta in 1782, with reference to the device's ability to store a higher density of electric charge than a normal isolated conductor" \$\endgroup\$ Commented Mar 11, 2016 at 23:25
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    \$\begingroup\$ Never, thought about it before. But it´s still called condenser in my language. Maybe it just fell out of style, like automobile->car. \$\endgroup\$
    – Dejvid_no1
    Commented Mar 11, 2016 at 23:26
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    \$\begingroup\$ @alex.forencich - I suspect that the reason for kmc is that "billion" means different things in different cultures. These days it's usually 1000 million, but it can also be 1 million million. \$\endgroup\$ Commented Mar 12, 2016 at 13:43
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    \$\begingroup\$ @alex.forencich: No, but take into account that the prefix giga was officialy introduced in the SI only in the 1960, with the resolution 12 of the 11th CGPM (though its first appearance seems to be around 1947) and thus in previous years it was not uncommon to have multiple prefixes like kilomega or micromicro, which in the current SI are deprecated. \$\endgroup\$ Commented Mar 12, 2016 at 17:28

4 Answers 4


As the term has been traced (thanks to @helloworld922) back to 1782, it's worth noting this is the year James Watt patented the compound steam engine, having conceived the separate condenser in 1765, and patented it and produced efficient condensing steam engines in the 1770s.

So the term was very much cutting edge at the time, and scientists tended to read much more widely across disciplines than we can possibly do today, so certainly Volta would have been aware of it.

In those days, electrical concepts were explained by analogy with fluid flow concepts, with pressure corresponding to voltage and current corresponding to ... current.

So, because a condenser absorbs large volumes of steam at very low pressure, it offers a good analogy for a device which can absorb a lot of charge at relatively low electrical pressure. (However the analogy breaks down when you try to recover the steam : the condenser can only deliver water!)

Interesting, while books of a hundred years ago talk of electrical pressure (measured in volts) and electrical current (measured in amps) we have dropped the former term in favour of "voltage", it still looks odd to see "amperage" instead of the word "current", and I can't recall seeing "ohmage" in place of "resistance".

The "Admiralty Handbook of Wireless Telegraphy" (1925 edition) consistently uses the term "condenser" while calling its storage capacity "capacity". The book introduces both the "practical unit" of the Farad, (millifarad, microfarad, and micromicrofarad, so apparently "pico" wasn't in use yet) and the "service unit" of the Jar. (by 1925, "electrical pressure" has given may to"Electro-Motive Force" or EMF, which is still occasionally seen in the wild today)

The original condensers were actually glass jars (Leyden jars), presumably of a standard size, because the book introduces the "service unit" which is the Jar, where 1 Jar = 1/900 uF. (It then goes on to inconsistently use jars and farads throughout the remainder of the book!)

So we have consistently dropped some of the contemporary terms, kept some others, and inconsistently dropped others - "condenser" is still the term in the spare parts catalog for my outboard motor while "capacitor" is seen elsewhere.

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    \$\begingroup\$ As we already started speaking about different languages, here is another one: In german, voltage is Spannung, which literally is tension \$\endgroup\$
    – sweber
    Commented Mar 12, 2016 at 12:59
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    \$\begingroup\$ @sweber Indeed, and we have high tension cables in English, though we never call voltage tension otherwise. Tension (pull) is the same as pressure (push) with the sign reversed! \$\endgroup\$
    – user16324
    Commented Mar 12, 2016 at 13:16
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    \$\begingroup\$ @Brian Drummond Don't forget high-tension transformers for tube equipment as well. \$\endgroup\$
    – AndrejaKo
    Commented Mar 12, 2016 at 13:45
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    \$\begingroup\$ The picoFarad was known as the micromicroFarad (uuF) until at least the 70s (at least in the old avionics I was repairing). \$\endgroup\$ Commented Mar 12, 2016 at 17:01

It seems the word comes from the latin condenseo which means to condense or to compress.

This does make sense because in contrast to a piece of wire, you can push charge into the cap without too much pressure (voltage). It seems the charge condenses inside like propane gas does, when it is pressed into a gas bottle.

By the way, the german word is Kondensator, and it has a Kapazität.

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    \$\begingroup\$ Same in Finnish, a kondensaattori has a kapasitanssi. \$\endgroup\$
    – wailashi
    Commented Mar 12, 2016 at 12:36
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    \$\begingroup\$ It is actually like that in many languages. The The World's Online Electrotechnical Vocabulary shows translations in different languages both for capacitor and capacitance. Capacitor is actually an exception among the reported translations. \$\endgroup\$ Commented Mar 12, 2016 at 14:14

The term condenser is still used for the capacitor in older automotive ignition systems. These used the condenser along with a 'coil' (as step-up transformer) and points (mechanical switch), to generate the spark from the 6 or 12 VDC available in engine charging systems. In modern cars the spark is generated electronically. AFAIK the mechanical systems were on their way out in the 80's, completely gone by the 90s as computer electronics took over most engine functions. But you can still buy condensers+points for old cars.

  • \$\begingroup\$ This is an insightful comment. However, it doesn't say where the term "condenser" came from in the first place. (By the way, Russian language uses the same word for capacitor and condenser: конденсатор.) \$\endgroup\$ Commented Jul 5, 2018 at 22:25
  • \$\begingroup\$ Good point. I agree with Brian Drummond's reply above, although I would add that the Leyden jar came about when it was thought electric charge might be some kind of fluid \$\endgroup\$
    – rickypam
    Commented Jul 7, 2018 at 0:55

Not that anyone cares, but "condenser" seems to have faded from use from the mid 1930s through about 1950. Dubilier was using capacitor by 1940 but Allied catalogs didn't switch to capacitor until around 1950.


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