# Magnetic field strength diminishes proportional to inverse cube or inverse square?

 Mentor P: 11,623 It depends on the source of the field and how close you are to it. A "monopole" field goes like $1/r^2$. Magnetic monopoles don't actually exist as far as we know to date, but some situations can produce a field which is approximately a monopole field over a limited region. For example, if you have a long bar magnet and you stay close to one pole. A "dipole" field goes like $1/r^3$. This is what you get from a current loop or a bar magnet, when you get far enough away that it appears "small."