In the
study of electricity, conductors and insulators were recognized.
There were demonstrations of electrical phenomenon such as seeing
brandy ignited by a spark shooting from a man's finger and
transferring an electrical impulse among a circle of people by
their holding hands. Electricity was stored in an early type of
capacitor. Benjamin Franklin "caught" lightning with a sharp
pointed wire attached on top of a kite which led down to a key.
When a thunder cloud electrified the kite, a charge could be seen
coming from the key to an approaching finger. This charge was
stored and then reproduced to create the same feeling of
electrical transference among hand-holders as a rubbed glass
globe, thereby illustrating that it was the same phenomenon as
electricity. This countered the theological belief that thunder
and lightning were signs of divine displeasure or the work of the
devil. He invented the lightening rod, which was then used to
protect houses. About ten years later, the first lightening rod on
an English church was erected. Franklin theorized that there were
electric charges everywhere and designated them as positive or
negative. He observed that opposite charges attracted each other,
but that like charges repelled each other. In 1766, Joseph
Priestly did an experiment suggested by Franklin and showed that
electrical force follows the same law as gravitational force; that
is, that the attraction or repulsion between two electrical
charges varies inversely to the square of the distance between
them.
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