What does the term impulse refer to in a turbine?

Impulse refers to the force generated by the impact of steam on the blades of a turbine. In an impulse turbine, high-velocity steam is directed at the blades, causing them to move as the steam expands and loses pressure upon impact. This mechanism relies heavily on the momentum transfer from the steam to the blades, resulting in rotational motion.

Understanding impulse in this context is crucial, as it highlights the operating principle of impulse turbines, where energy is converted from the kinetic energy of the steam to mechanical energy in the form of rotation. The other options relate to different aspects of turbine operation, such as pressure or thermal energy, but do not accurately capture the specific definition of impulse in this context.