Magnetic energy density
= Magnetic energy density
{title2=$u_B=B^2/(2\mu_0)$}
In vacuum or an approximately nonmagnetizable plasma, the field <energy> per volume is $B^2/(2\mu_0)$. <magnetic pressure> has the same scale, but a <magnetic field> also exerts directional tension, so its stress is not universally an isotropic pressure. Material magnetization can require a different constitutive treatment.