A turbine where the steam pressure drops only in stationary blades is called an impulse turbine.

• A. True
• B. False
• C. Not applicable
• D. Not sure

Answer: (A)

In an impulse turbine, the steam’s pressure is dropped primarily in stationary nozzles before it reaches the rotor. Those nozzles convert enthalpy to high-velocity steam, and the rotor blades (impulse blades) mainly change the direction of the jet and impart momentum to the moving blades. Because most of the pressure drop happens in the fixed blades, the pressure on the moving blades remains nearly the same, so the turbine’s work comes from momentum transfer rather than a pressure drop across the moving blades. That’s why the statement is true.

If someone were thinking of a reaction turbine, they’d expect pressure to drop over both stationary and moving blades, which is different. The other choices don’t describe the typical behavior of impulse turbines, so they aren’t appropriate.