|Heinrich Barkhausen electromagnetism|
The quantum of magnetization in ferromagnetic material is not the atom with its two tiny poles but irregular bunches of atoms that align together called domains. Heinrich Barkhausen found that changes of magnetization did not happen continuously, but in random steps as each magnetic domain resists being realigned or is caught on defects in the crystal lattice, but then suddenly gives way, one after another, producing irregular avalanches of magnetic noise.
Operators using Marconi’s magnetic detector had to endure the crackling, breathing of Barkhausen noise, but without knowing what caused it. Marconi’s detector was discontinued around 1912.
In this one the physicists were behind the inventors, explaining, not predicting. But once inventors learned the science, they could use it to test metals for imperfections and mechanical stress.