Electrodynamics Definition and 405 Threads

May anyone please show me how to derive the "magnetic field energy density" in a medium, which equals \frac{1}{2}H \cdot B? I would be very pleased if anyone could show me how to derive (step-bystep) the conservation of energy equation *in a medium* (not in vacuum) i.e. \nabla\cdot S +...

One question has disturbed me long time, I don't know the distinction between quantum electrodynamics and quantum field theory. By the way, which quantum field theory or quantum electrodynamics textbook is prefer?

Hi, This is my first post, am excited to be here. Cutting to the chase here, i have a question that has been bothering me for a while. The problem is there is a charged cylinder with charge say +1, and i have to charges outside say at a distance 'd' from the center of the cylinder such that...

A metal bar of mass m slides frictionlessly on two conducting rails a distance l apart as shown in the attached Figure 1. A resistor R is connected across the rails and a uniform magnetic field B, directed into the page fills the entire region. a) If the bar is moving to the right at speed...

Im wondering what products/technologies that would not have been poosible without the theories of Quantum electrodynamics, not things that these theories appear to explain.