A Langmuir probe is a scientific instrument used to measure the electrical properties of plasmas, which are ionized gases consisting of charged particles. It typically consists of a thin metal wire or rod that is inserted into the plasma. By applying a voltage to the probe, researchers can collect data on electron density, temperature, and other important characteristics of the plasma. Langmuir probes work by measuring the current that flows between the probe and the plasma as the voltage is varied. This current-voltage relationship helps scientists understand the behavior of the plasma and is essential in fields like fusion research, space physics, and semiconductor manufacturing.