Re: Those kids behind Benjamin Franklin.

In a recent message "Victor Manta" <manvic_99spaam@xxxxxxxxx> wrote:

"rodney" <pookiethai@xxxxxxxxxxxxxx> wrote in message
news:482309b6$0$89003$c30e37c6@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Well we left no stone unturned,
but still the mystery remains as far as I am concerned.
Are they kids or Political cartoons? and what is that machinery?
http://cjoint.com/data/fiqgc8Sp6g.htm


The letter form the Franklin Institute

Dear :

The Franklin Institute has, in its collection, the painting on
which
the 3 cent stamp was based. On close inspection of the painting, the Chief
Curator noted that the objects to which you were referring were; an 18th
century electrical apparatus, most likely an electrostatic machine, and a
Leyden Jar for storing electrical charge.
I hope this begins to answer your question. Thank you for your
interest in the collections of The Franklin Institute.


Rodney,


A number of machines have been developed to 'automate' the separation of charge by
induction, and to transfer these charges to a capacitor, which in the early days
was usually a Leyden Jar.

A classic device is the Wimshurst Machine, which I used to use when teaching physics.
It could readily produce intense sparks jumping several inches, but the current
involved in charging up the Leyden Jars is very small. A spark needs about 3000
volts per mm to jump across an air gap, so 2 inches needs about 150,000 volts.

In my first year of teaching I tried to demonstrate this by getting the entire class
to hold hands, whith the end pupils holding the Leyden Jars at each side.

I then started turning the handle, and this had no discernable effect
until one boy at one end let go of the Leyden Jar.

That was his first mistake.

His second, and more serious, mistake was to then touch the jar again
about two seconds later, by which time the jar had charged up significantly.

The entire class jumped two feet in the air.

Fortunately all survived the experience, and I learnt not to try that
particular demonstration again (the Risk Assessment was too dire!!!)

Several experimenters tried to emulate Franklin's experiment, and died.
So too would Franklin, if he had actually put his hand that close to the key.
I believe he actually held the kite string and key with a silk ribbon,
and got the spark to jump onto the electrode of a Leyden Jar.

--
Tony Clayton tony.clayton.1962@xxxxxxxxxxxxx
Coins of the UK : http://www.coins-of-the-uk.co.uk
Sent using RISCOS on an Acorn Strong Arm RiscPC
.... Monday is the root of all evil!
.

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