Elevator down

 "My personal desire would be to prohibit entirely the use of alternating currents. They are unnecessary as they are dangerous...I can therefore see no justification for the introduction of a system which has no element of permanency and every element of danger to life and property."

Thomas Alva Edison, on alternating current

Of all the topics studied in a high school survey course, electricity is probably the one that students approach with greatest enthusiasm. While electricity is an important part of our existence, it is deliberately hidden from any close inspection as part of life's infrastructure. Because 120V AC is lethal. we place ample barriers between people and charge carriers. For many scholars enrolled in this course, these few weeks are a tentative first step into things electric.

A thorough study of electricity will show that what we sense to be important about this topic has gone through a metamorphosis, not once but several times. The eighteenth century was taken up with collecting static charge in a container to study its properties, as one might collect a fluid. At the beginning of the nineteenth century, electricity was on the move, flowing as it did from the positive terminal of Volta's direct current battery. By 1831 Farraday had discovered a way to make a current (still composed of positive charge) alternate in direction while varying in magnitude. AC would languish as a laboratory curiosity for 50 years and more before coming into its own with the help of Tesla and Westinghouse. Finally, we came to understand (for now, at least) that it is the negative charges in atoms that are doing all the moving and all the work after all.

For those students who absolutely need to know the "right" answer or the ultimate truth, the history of the development of electric theory should show that cutting-edge theories, despite being defended by the greatest minds of the time, are transitory at best.

A. Electric Fields and Forces

B. Potential and potential energy

C. Ohm's Law - DC Circuits

D. The Magnetic Field

E. Electrodynamics

F. AC vs DC

G.  The Residential Wiring Laboratory

H. Summary

These sites are links to an entire course in E & M




Click on PHYSICS PEOPLE to find a list of people who have made a significant contribution to electricity & magnetism. A writing assignment awaits you there.

References - For useful references regarding this topic, go to REFERENCES.

Last edited 02/18/06

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