Electromagnetic energy
= Electromagnetic energy
{title2=$U_{\rm EM}$}
In vacuum the electromagnetic energy density is
$$
u=\frac{\varepsilon_0E^2}{2}+\frac{B^2}{2\mu_0},
$$
and the field energy in a region is $U_{\rm EM}=\int u\,dV$.
= Electromagnetic energy
{title2=$U_{\rm EM}$}
In vacuum the electromagnetic energy density is
$$
u=\frac{\varepsilon_0E^2}{2}+\frac{B^2}{2\mu_0},
$$
and the field energy in a region is $U_{\rm EM}=\int u\,dV$.