This week is going to be heavy with reading primary sources.
First, there are some brief readings on Thales, or at least what Aristotle tells us about Thales, souls, and amber.
Next, an interesting reading on the thoughts from the mid-19th century A guide to the scientific knowledge of things familiar by Brewer. An interesting 1840s version of Macaulay’s The Way Things Work. The Brewer text shows the strength of the idea of heat and electricty as fluids, building on yesterday’s discussion of the atomism of Democritus versus the plenum of Descartes and Aristotle. I also like the mention of the two forms of electric fluid.
Another nice reading is William Gilbert of Colchester, physician of London:On the load stone and magnetic bodies. He talks about the differences between magnetism and the electric force. He gives a nice summary of all the types of stones which can cause the electric force. On p 79 he introduces his instrumentation for measuring this electric force, which is a simple instrument you can easily build at home to do experimentation. It is worth it to start reading on p74.
As Tesla says, Gilbert was the first to really make the study of electricity scientific and empirical, although there probably had been electrostatic generators, capacitors, and Leyden jars for centuries before that time.
The important pieces to take away from the textbook are:
Positive charge is carried by protons which are generally locked in the nucleus of atoms
Negative charge is carried by electrons which are freer to move about.
Objects are generally neutral because the positive and negative charges in an object balance out.
When an object is positively or negatively charged, it either has a deficit or excess of electrons.
As we studied Newton’s Universal Law of Gravitation, there is a similar law for the electric force called Coulomb’s Law.
The strength of the electric force depends on the quantity of charge and the location of the charges.