Grommet be used purely decoratively for crafting. When used in sailing and various other applications, they are called cringles. Sometimes field workers refer to them as grunyons. If metal or another hard material has a hole made in it, the hole will probably have sharp edges. Electrical wires, cord, rope, lacings, or other soft vulnerable material passing through the hole can become abraded or cut, or electrical insulation may break due to repeated flexing at the exit point. Rubber, plastic or plastic coated metal grommets are used to avoid this. The grommet could also protect the wiring/cabling from contamination from dirt,
Particle in a ring Particle in a ring In quantum mechanics, the case of a particle in a one-dimensional ring is similar to the particle in a box. The Schrödinger equation for a free particle which is restricted to a ring (technically, whose configuration space is the circle formula_1) is Using polar coordinates on the 1-dimensional ring of radius R, the wave function depends only on the angular coordinate, and so Requiring that the wave function be periodic in formula_4 with a period formula_5 (from the demand that the wave functions be single-valued functions on the circle), and that they be normalized leads to