In the macroscopic equations, the influence of bound charge Q b and bound current I b is incorporated into the displacement field D and the magnetizing field H, while the equations depend only on the free charges Q f and free currents I f. This reflects a splitting of the total electric charge Q and current I (and their densities ρ and J) into free and bound parts: Q = Q f + Q b = ∭ ∭ Ω Ω ( ρ ρ f + ρ ρ b ) d V = ∭ ∭ Ω Ω ρ ρ d V , I = I f + I b = ∬ ∬ Σ Σ ( J f + J b ) ⋅ ⋅ d S = ∬ ∬ Σ Σ J ⋅ ⋅ d S .