A piece of metal terminating in metallic wires, or strips of flexible metal, used for securing good metallic connection between two portions of an…

see contact block n.

a ring of conducting material which is attached to and rotates with a shaft, so that electric current may be transferred to a stationary circuit…

Of things: An apparatus, vessel, etc., used for collecting something (variously applied in technical use). So collector ring, collector shoe (see…