31 Introduction
Organizing Principle for this Unit
Physics sees beauty in simplicity. Meanwhile biology sees beauty in complexity.
– I heard this somewhere, but I cannot find the source
I think this quote sums things up nicely. In biology, we look with wonder at the huge diversity of life on Earth and all the solutions evolution has developed over the eons. In physics, as I hope this course has demonstrated, we like to try to explain as many different phenomena with the smallest number of ideas. I feel that this is summarized nicely in the video below:
Unlike prior units, which had an explicit connection to your other courses we were exploring, this unit is about really all about physics’ idea of beauty in simplicity. In this unit, we will bring together all of the different ideas that we have talked about over the duration of this course: light, electrons, charge, wave-particle duality, electric field, and potential into a beautiful whole showing that everything is connected to everything else!
Introduction to Magnetism
One evening, an Alaskan sticks a note to his refrigerator with a small magnet. Through the kitchen window, the Aurora Borealis glows in the night sky. This grand spectacle is shaped by the same force that holds the note to the refrigerator.
People have been aware of magnets and magnetism for thousands of years. The earliest records date to well before the time of Christ, particularly in a region of Asia Minor called Magnesia (the name of this region is the source of words like magnetic). Magnetic rocks found in Magnesia, which is now part of western Turkey, stimulated interest during ancient times. A practical application for magnets was found later, when they were employed as navigational compasses. The use of magnets in compasses resulted not only in improved long-distance sailing, but also in the names of “north” and “south” being given to the two types of magnetic poles.
Today magnetism plays many important roles in our lives. Physicists’ understanding of magnetism has enabled the development of technologies that affect our everyday lives. The iPod in your purse or backpack, for example, wouldn’t have been possible without the applications of magnetism and electricity on a small scale.
The discovery that weak changes in a magnetic field in a thin film of iron and chromium could bring about much larger changes in electrical resistance was one of the first large successes of nanotechnology. The 2007 Nobel Prize in Physics went to Albert Fert from France and Peter Grunberg from Germany for this discovery of giant magnetoresistance and its applications to computer memory.
All electric motors, with uses as diverse as powering refrigerators, starting cars, and moving elevators, contain magnets. Generators, whether producing hydroelectric power or running bicycle lights, use magnetic fields. Recycling facilities employ magnets to separate iron from other refuse. Hundreds of millions of dollars are spent annually on magnetic containm