Mating electrical contacts separated by conductors. They are open when pulled apart and electrically connected when mated.
Not kidding. Some work great, some not so well.
Good ones are made from or plate with corrosion resistant material that is somewhat soft to allow more mating area. Gold and silver are great, but expensive. The connecting surfaces should be pressed together with some sort of sprint. Multiple contact zones each with their own spring device are great. Ideally the spring(s) is outside the current path so that it doesn’t heat and lose temper. The two mating contacts should wipe across each other as the connection is mated, as this will wipe off foreign matter as well as minor surface corrosion. The contacts should fasten securely to the wires, both for low electrical resistance and reliability, but also so that the wire can carry some of the heat away from the contacts. The wires should be mechanically supported beyond the electrical connection point so that force or motion of the wire doesn’t disturb the electrical connection.
Many applications will compromise on connectors due to cost, installation difficulty, weight, size, lead time, etc. Connectors that will only be mated a few times over the product lifetime can be much simpler than those requiring frequent mating.
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