For the simple theory of a single real scalar field $\phi$ in 1+1D, the Lagrange density is $$\mathcal{L}=\frac{1}{2}\partial_\mu\phi\partial^\mu\phi-U(\phi)\tag{1}$$ with Minkowski signature $(+,-)$, and the corresponding Hamiltonian is $$\mathcal{H}=\frac{1}{2}\partial_\mu\phi\partial^\mu\phi+U...

I'm in an electromagnetism class and struggling with a concept. The textbook derived several equations which state that the wave velocity of an electrical signal in a transmission line depends on the permittivity and magnetic permeability of the insulator. Why is it the insulator's permittivity...

I was looking for a definition of mass and most of the time what I got was that "it is the amount of matter". Now that is very vague. And the way we define matter is "anything that has "mass" and occupies space". so... what exactly is mass? Can you please answer it to the level where a highschool...