Magnetostatics is the study of
magnetic fields in systems where the
currents are steady (not changing with time). It is the magnetic analogue of
electrostatics, where the
charges are stationary. The magnetization need not be static; the equations of magnetostatics can be used to predict fast
magnetic switching events that occur on time scales of nanoseconds or less. Magnetostatics is even a good approximation when the currents are not static — as long as the currents do not alternate rapidly. Magnetostatics is widely used in applications of
micromagnetics such as models of
magnetic recording devices.