What is the basic principle of a steam turbine?

The basic principle of a steam turbine revolves around the expansion of steam and its ability to convert thermal energy into mechanical energy. When steam is generated in a boiler, it travels to the turbine where it encounters a series of blades attached to a rotating shaft. As the high-pressure steam passes over the blades, it expands and accelerates, resulting in a change in momentum. This interaction between the steam and the blades causes the turbine shaft to rotate, ultimately converting the energy from the steam into mechanical work.

The effectiveness of this operation lies in the steam's expansion, which reduces its pressure and temperature as it moves through the turbine. This principle is fundamental in the generation of electricity in power plants, where the mechanical energy produced by the steam turbine drives a generator.

Other concepts like steam cooling and condensing, steam compression, or using steam solely for heating pertain to different aspects of steam systems but do not encapsulate the core operational principle of a steam turbine. The process described in the correct answer highlights the direct relationship between steam flow and mechanical motion, which is foundational to steam turbine functionality.