The first permanent alloy magnets of aluminum, nickel and cobalt (alnico magnets) are produced.
British physicist Alan Wilson applies the band-gap theory of energy to account for the behavior of superconductors and insulators.
The first cyclotron, a circular particle accelerator in which subatomic particles are accelerated by an alternating high-frequency electric field in a fixed magnetic field, is built.
German physicist Ernst Ruska, while still a student in Berlin, constructs the first electron lens, using an electromagnet to focus a beam of electrons just as a lens focuses a beam of light. By 1933, he uses several electron lenses in a series to make the first electron microscope with better definition than a light microscope.
James Chadwick of England discovers the neutron, a particle with mass similar to a proton, but that does not have an electrical charge.
American physicist Carl Anderson discovers the positron, a particle with mass similar to an electron, but with a positive rather than negative charge.
Walther Meissner and Robert Oschenfeld of Germany discover that as a material loses its resistance to electricity when its temperature is dropped below a certain temperature, the magnetic field inside the material is completely or partly expelled. Characteristic of all superconductors, this phenomenon came to be commonly known as the Meissner effect or the Meissner-Oschenfeld effect.
Sodium vapor lamps come into use to light highways.
German inventor Semi Joseph Begun constructs the first magnetic tape recorder used for broadcasting.
In the United States, the coiled-coil filament is invented, resulting in brighter and more energy-efficient electric light bulbs.
Magnetic tape for audio recording becomes available commercially in Germany following its introduction at the Berlin Radio Exhibition.
French physicist Louis Néel develops the concept of antiferromagnetism, a temperature-dependent form of magnetism in which adjacent ions arrange themselves in antiparallel formations so that nearly no overall external magnetism can be detected.
Walter Elsasser, a German-born American physicist, proposes that the Earth’s observable magnetic field is the result of rotation-related eddy currents in the liquid core of the planet.