1. Exploring Electrical Technology Era of Early Electrical Science Part II: “Jarring Electricity”

2. Summary of 17 th Century & Electricity  Attempts by Jesuits to contribute to understanding during this 1 st Period  Printing Press: had been available since the mid 1400s, so by 1600s many works were readily published (after ~3 years)  New Inventions: telescope, microscope, time- keeping devices, thermometer, air pump, various machines and use of water and wind to power them

3. Summary of 17 th Century & Electricity  Development of patent laws  During the mid 1600s  Aided in getting credit where it is due  Establishment of the first Academies  In France (1660)  In England (1662)

4. Summary of 17 th Century & Electricity  Humorous instances of science starting and stopping during this time  As an illustration, consider an observation made by Newton in 1675 to the Royal Society of London...  Read from 1 st selection in your coursepack @ top of p. 168 Heilbron, J.L. Elements of Early Modern Physics. Berkeley: University of California Press, 1982.  Conclusions: less than 300 years ago, understanding about electricity amounted to realizing that  its attractive force was different from magnetic attraction  it could be generated, and as a curiosity it was popular, but little progress was made in the way of theorizing about it.

5. Early 18 th Century (2 nd Period: 1700-1740)  Hawksbee  An English instrument maker and member of the RSL  In 1706* he created a special glass tube  A more efficient static electric generation device  Able to demo. electrostatic repulsion & attraction  He did not interpret repulsion as related to electrification (held to Cabeo’s theory) * Note that this was the year as Ben Franklin’s birth.

6. Early 18 th Century (2 nd Period: 1700-1740)  Other notable people & developments  Isaac Newton, the most famous and notable member of the RSL at the time, commented in 1710 that most of the phenomena observed as a result of friction on glass was the effect of electric attraction, and not any other force such as repulsion  The glass tube became the standard for generating electrostatic forces, and it was the type of instrument that Ben Franklin obtained in 1745 which stimulated his interest in electricity

7. Early 18 th Century (2 nd Period: 1700-1740)  Gray  A dyer by trade  Discovered that electricity can flow and be transmitted from one object to the next over a distance by certain materials (conductors*)  Read 2 Parag’s from Heilbron (pp. 172, 173)

8. Early 18 th Century (2 nd Period: 1700-1740)  Gray and his group  Began to notice the difference between materials through which electricity flows easily and materials which offer opposition to electric conduction  Had a theory that (unfortunately) continued to confuse the mechanism of electric conduction with the forces of attraction at a distance  Good “conductors”: water, an umbrella, wires & skin  Good “insulators”: glass, silk, hair and resin  The Charity Boy demo (see Heilbron p. 173) was a common one to show various electrical properties

9. Early 18 th Century (2 nd Period: 1700-1740)  Hawksbee threatened by Gray’s work  Hawksbee, at the RSL, after learning of Gray’s work, put two of Gray’s observations forth as his own, and the rest he suppressed  Motivation: his livelihood may have come largely from his work for the RSL, and he may have felt he could not afford to encourage rival experimentalists How could Hawksbee have turned Gray’s work into something more positive for himself and others?

10. Early 18 th Century (2 nd Period: 1700-1740)  Conductor and Insulator  Not terms actually used by Gray  1 st used by Desaguliers in 1739  French English physicist  Also repeated many of Gray’s experiments  Good experimental science  Results testable (known procedure)  Results repeatable (rather than incidental) If a faithful and reliable God did not create all the universe and its contents then how could we expect any consistency, reliability or repeatability?

11. Early 18 th Century (2 nd Period: 1700-1740)  Dufay  French member of Academy of Sci. in Paris  Duplicated & confrm’d many demos by Gray  Contributed more precise theory on phenom.  Proposed a “2-fluid” theory of electricity  “Vitreous” & “resinous” elements  Like elements repel and unlike attract  Set stage for controversy w/ Franklin’s view

12. End of Early 18 th Century (2 nd Period: 1700-1740)  Electricity grows more popular  In 1740, electricity was a rather small part of the topics covered in public lectures, but by 1745 it became the “rage”  This change creates a transition from Heilbron’s 2 nd to 3 rd Period  Electricity entertains  Heilbron p. 179, middle bottom  Heilbron p. 180 Practical Jokes

13. Mid 18 th Century (3 rd Period: 1740-60)  During the early part (~1740-1745)  Ben Franklin  Visited in Boston and again in Philadelphia  Heard his first public lectures & demos of electricity by Dr. Archibald Spencer (a demo similar to Gray’s suspended charity boy)  Leiden Jar invented separately by two men  Von Kleist (1745 in Pomeria, Poland)  Van Musschenbroek (1746 in Leiden, Holland)

14. Mid 18 th Century (3 rd Period: 1740-60)  The Leiden Jar  Underscored how strong the fluid view of electricity had become; if a fluid, then why not store it like one?  Raised demonstrations and experiences with electricity to new heights, temporarily  Read of experiences with the Leiden Jar from Heilbron, pp. 184-185.  All this sets the stage for Ben Franklin