Lecture Playlist

The Lorentz transformation

Adding velocities

Relativistic laws of motion and E = mc^2^

Classical field theory

Particles and fields

The Lorentz force law

The fundamental principles of physical laws

Maxwell's equations

Lagrangian for Maxwell's equations

Connection between classical mechanics and field theory
After a brief review of gauge invariance, Professor Susskind describes the introductory paragraph of Einstein's 1905 paper "On the Electrodynamics of Moving Bodies," and derives the results of the paragraph in terms of the relativistic transformation of the electromagnetic field tensor. This paragraph asks the fundamental question "what is the difference between a charge moving in a magnetic field, and a fixed charge in a changing magnetic field." The answer to this fundamental question must be "nothing" if the principle of relativity is true. This conclusion is what led Einstein to develop the special theory of relativity.
Professor Susskind then moves on to present Maxwell's equations. He discusses the definition of charge and current density that appear in them, and then derives the relationship between these quantities. This relationship is the continuity equation for charge and current, and represents the principle of charge conservation.
The lecture concludes with the presentation the first two Maxwell equations in relativistic notation. This single equation is the Bianchi identity, and this identity makes it clear that magnetic charge sources (monopoles) and magnetic current do not exist.
 Relativistic transformation of the electromagnetic field tensor
 Maxwell's equations
 Conservation of charge
 Maxwell's equations in relativistic notation
 Magnetic monopole