View Full Version : One-question quiz #1

10-12-2014, 06:24 PM
For many years, the Royal Navy bought all capacitors (for use in its radios) in jars. Why?

24 hour rule.

10-12-2014, 07:01 PM
Because capacitors were made with cardboard. Moisture would cause the capacitance to change. The jar helped keep the moisture out.

10-12-2014, 07:28 PM
Because the Minister of the Royal Navy, Admiral Winston Churchhill, had a cousin, the Earl of Worstershire, whose industrial empire manufactured glass jars. It was political. And delayed the development of the zip lock bag by 75 years.

The sailors then would make homemade rum and store the booze in the discarded jars. The radioman on a destroyer was nearly as popular as the cook.

10-12-2014, 08:52 PM
Ummm -- try again, guys.

10-12-2014, 09:18 PM
And don't forget the 24 hour rule.

For those unfamiliar, serious responses are held back for 24 hours in order to allow all members to participate.

10-12-2014, 11:07 PM
Since I know the answer I will wait until 6:25pm Monday. Very clever Carl! They quit that purchasing method in the early 1950's.

10-13-2014, 03:45 PM
Since I know the answer I will wait until 6:25pm Monday. Very clever Carl! They quit that purchasing method in the early 1950's.

And I'll hold off until you have posted.

10-13-2014, 04:20 PM
Oh, the suspense!!

10-14-2014, 07:37 AM
Nowadays we buy capacitors in farads, μF, and pF. But in the early years of radio, capacitances were often stated in jars.

From the (British) Admiralty Handbook of Wireless Telegraphy, 1931:

The jar is the Service unit, and is very useful when dealing with the small capacities met with in ordinary wireless practice.

1 farad = nine hundred million jars
1 μF = 900 jars

Variable capacitors were difficult to make in the early 20th century, and transmitters were tuned by adding or removing fixed capacitors in parallel. Almost always, each of these capacitors was a Leyden jar and actually consisted of a thin-walled glass jar with metal (foil or plating) on the inside and outside surfaces. Operators would add or remove capacitance by hooking and unhooking connections to the jars, and often prepared tables listing how many Leyden jars to use for each operating frequency.

Soon the Leyden jars became more or less standardized, and a typical one had a capacitance of about 1111 pF. This value of capacitance came to be called a jar, and the Royal Navy used this as a standard unit until 1937, when it was made obsolescent in order to align Royal Navy practice with commercial practice. Some of the fleet may have used the jar as a unit of measurement as late as the early 1950s.

I believe, without being certain, that the US. Navy also specified capacitance in jars in the early 20th century.

10-14-2014, 02:36 PM
I completely forgot about the answer. I got busy fixing supper and didn't remember until I was in bed. Yep, the measurement of capacitors was in Jars instead of farads.

10-14-2014, 03:02 PM
Was supper something that came in jars?

10-14-2014, 07:29 PM
I was going to guess (surmise, postulate) that the caps were placed in jars to avoid them creating a spark on board a vessel which carried a large supply of black power and other high explosives.

But then they ran them with coal or oil fired boilers, so what real difference would that have made? :think:

Good question though, Carl.

10-14-2014, 11:18 PM
I'll have to confess, Google comes through in the tough ones.

10-15-2014, 03:24 AM
Well I ran this through my gray matter for 48 hours and barely resisted the temptation of Google.

Never would have guessed Leyden jars. Never. Like others above I was thing jars as packing containers for safety, sparks, humidity, shelf life, and on and on. None of it seemed right though and without EVER seeing any NOS on eBay for capacitors packed in jars in "Naval minty" condition :jitter:, I knew I was running in the wrong circle.

Unit of measure. Approximately a nanofarad. Whoda thunk it :D? Great quiz question, Carl.

10-15-2014, 08:15 AM
Lends a whole new meaning to the term "JAR HEAD", no slam intended .