In theory, impulse turbines have which characteristic regarding pressure on moving blades?

• A. Can only use low-pressure steam
• B. Have no pressure drop through the moving blades
• C. Have a velocity drop through the nozzle
• D. Develop the most torque of all turbines

Answer: (B)

In impulse turbines, energy transfer to the rotor comes from changing the direction of a high-velocity steam jet, while the pressure drop happens mostly in stationary nozzles. The steam is expanded in the nozzle to convert pressure energy into kinetic energy, and by the time it reaches the moving blades, the pressure on the blade surfaces remains essentially the same from inlet to outlet. So, in theory, there is no pressure drop through the moving blades. This contrasts with reaction turbines, where pressure falls across both stationary and moving parts. The other statements don’t fit because impulse turbines don’t require low-pressure steam, the nozzle—not the rotor—causes the velocity increase, and torque isn’t the defining feature—it's the momentum exchange with minimal rotor pressure change.