Toroidal inductors and transformers:
Toroidal inductors and transformers are inductors and transformers which use
magnetic cores with a toroidal (ring or donut) shape. They are passive electronic
components, consisting of a circular ring or donut shaped magnetic core of
ferromagnetic material such as laminated iron, iron powder, or ferrite, around
which wire is wound.
Although closed-core inductors and transformers often used cores with a square
shape in the past, the use of toroidal-shaped cores has significantly increased
because of their superior electrical performance. The advantage of the toroidal
shape is that, due to its symmetry, the amount of magnetic flux that escapes
outside the core (leakage flux) is low, therefore it is more efficient and thus
radiates less electromagnetic interference (EMI).
Toroidal inductors and transformers are used in a wide range of electronic
circuits: power supplies, inverters, and amplifiers, which in turn are used in
the vast majority of electrical equipment: TVs, radios, computers, and audio systems.
Source:
https://en.wikipedia.org/wiki/Toroidal_inductors_and_transformers
Ferrite:
Ferrite is a ceramic material made by mixing and firing large proportions of
iron oxide blended with small proportions of one or more additional metallic
elements, such as strontium, barium, manganese, nickel, and zinc. They are
ferrimagnetic, meaning they can be magnetized or attracted to a magnet.
Source:
https://en.wikipedia.org/wiki/Ferrite_(magnet)
Gauss (G) or Tesla (T):
The gauss, symbol G (sometimes Gs), is a unit of measurement of
magnetic induction, also known as magnetic flux density. The unit is part of the
Gaussian system of units, which inherited it from the older CGS-EMU system. It
was named after the German mathematician and physicist Carl Friedrich Gauss in
1936. One gauss is defined as one maxwell per square centimetre.
As the cgs system has been superseded by the International System of Units (SI),
the use of the gauss has been deprecated by the standards bodies, but is still
regularly used in various subfields of science. The SI unit for magnetic flux
density is the tesla (symbol T),[1] which corresponds to 10,000gauss.
Source:
https://en.wikipedia.org/wiki/Gauss_(unit)