# Inductive wireless mobile charger circuit

In wireless mobile charging circuit, is there any formula of spacing which varifies that by increasing diameter and turns, spacing (range) can be increased?

$$L_{12} = N_1.N_2.\frac{\mu_0}{2}.r_1.r_2.\int_0^{2\pi}\dfrac{cos\alpha}{\sqrt{b^2+r_1^2+r_2^2-2.r_1.r_2.cos\alpha}}d\alpha$$
Being $b$ the axial spacing, $r_i$ the radius of the coils and $N_i$ the number of turns. You can see how increasing the number of turns and radius will allow you to increase the axial distance to obtain the same coupling inductance, therefore the same transfered power.