A carbon brush is a sliding contact used to transmit electrical current from a static to a rotating part, in a motor or generator, and as regards DC machines, ensure a spark-free commutation.
A Thermocouple is a sensor used to measure temperature. Thermocouples consist of two wire legs made from different metals. The wires legs are welded together at one end, creating a junction. This junction is where the temperature is measured.
A crucible is a container that can withstand very high temperatures and is used for metal, glass, and pigment production as well as a number of modern laboratory processes.