What is the primary function of steam in power generation?

• A. To transfer heat to the environment.
• B. To cool the reactor.
• C. To generate magnetic fields in the generator.
• D. To turn the turbine and produce electricity.

Answer: (D)

Steam’s job in a power plant is to carry energy from the heat source and use it to do work. When high‑pressure steam expands through the turbine, it pushes the turbine blades, turning the turbine. That rotational (mechanical) energy is then converted into electrical energy by the generator connected to the turbine. So the primary function is to turn the turbine and drive electricity production.

Other options aren’t the main role of steam in this setup: transferring heat to the environment happens as heat is rejected from the cycle, not as its core purpose; cooling the reactor is a separate function of the plant’s cooling system; generating magnetic fields is achieved by the generator’s components, not by steam itself.