A proton, an electron, and a Helium nucleus, have the same energy. They are in circular orbits in a plane due to magnetic field perpendicular to the plane. Let ${\mathrm{r}}_{\mathrm{p}},{\mathrm{r}}_{\mathrm{e}}$ and ${\mathrm{r}}_{\mathrm{H}\mathrm{e}}$ be their respective radii, then,