### Course Introduction

The physics of the universe appears to be dominated by the effects of four fundamental forces: gravity, electromagnetism, weak nuclear forces, and strong nuclear forces. These forces control how matter, energy, space, and time interact to produce our physical world. All other forces, such as the force you exert in standing up, are ultimately derived from these fundamental forces.

We have direct daily experience with two of these forces: gravity and electromagnetism. Consider, for example, the everyday sight of a person sitting on a chair. The force holding the person on the chair is gravitational, and that gravitational force balances with material forces that "push up" to keep the individual in place. These forces are the direct result of electromagnetic forces on the nano-scale. On a larger stage, gravity holds the celestial bodies in their orbits, while we see the universe by the electromagnetic radiation (light, for example) with which it is filled. The electromagnetic force also makes possible the advanced technology that forms much of the basis for our civilization. Televisions, computers, smartphones, microwave ovens, and even the humble light bulb are made possible by control of electromagnetism. The average physics major will spend more time understanding and applying the concept of electromagnetic force than he or she will spend studying any other type of force.

The classical (i.e., non-quantum) theory of electromagnetism was first published by James Clerk Maxwell in his 1873 textbook A Treatise on Electricity and Magnetism. A host of scientists during the nineteenth century carried out the work that ultimately led to Maxwell's electromagnetism equations, which is still considered one of the triumphs of classical physics. Maxwell's description of electromagnetism, which demonstrates that electricity and magnetism are different aspects of a unified electromagnetic field, holds true today. In fact, Maxwell's equations are consistent with relativity, which was not theorized until 30 years after Maxwell completed his equations.

In this course, we will first learn about waves and oscillations in extended objects using the classical mechanics that we learned about in PHYS101. We will also establish the sources and laws that govern static electricity and magnetism. A brief look at electrical measurements and circuits will help us understand how electromagnetic effects are observed, measured, and applied. We will then see how Maxwell's equations unify electric and magnetic effects and how the solutions to Maxwell's equations describe electromagnetic radiation, which will serve as the basis for understanding all electromagnetic radiation, from very low frequency, long wavelength radio waves to the most powerful astrophysical gamma rays. We will briefly study optics, using practical models largely consistent with the predictions of Maxwell's equations but that are easier to use. Finally, this course provides a brief overview of Einstein's theory of special relativity. We will assume that you have a basic knowledge of calculus. You may decide to refresh your knowledge with Saylor Academy's MA101 course, but the most important concepts from vector calculus and differential equations will be covered in Unit 1 of this course.

This course will require you to complete a number of problems. Unlike mechanics, most of the phenomena encountered in the field of electromagnetism are not found in everyday experience - at least, not in a form that makes the actual nature of the phenomena clear. As a result, learning electromagnetism involves developing intuition about a rather unintuitive area of physics. In the end, developing physical intuition is less about getting a right answer than it is about getting a wrong answer and then understanding why it is wrong. In an ideal situation, this course would require you to both work out problems concerning the phenomena and observe various important phenomena in the laboratory. However, because this is an online course, we do not have the luxury of lab sessions. We have included a number of interactive demonstrations to compensate for this. When you approach a problem, try to work out the size of those quantities that clarify the basic nature of the question proposed. Thinking of these numbers as data from an ideal laboratory will help you develop a sense of how electromagnetism works – a sense that most people do not get from the mathematical description of the physics.