What is the function of a pneumatic actuator in a machine?

• A. To pressurize the hydraulic system
• B. To convert electrical energy into heat
• C. To filter air
• D. To convert compressed air energy into controlled linear or rotary motion.

Answer: (D)

A pneumatic actuator uses the energy in compressed air to create motion, delivering controlled linear or rotary movement. When air at pressure acts on a piston or rotor, it converts that pressure energy into mechanical work that can push, clamp, lift, or rotate components. This is why the best description is that it turns compressed air energy into controlled linear or rotary motion. The other options describe tasks for different components—pressurizing a hydraulic system requires a pump, converting electrical energy into heat is done by heaters, and filtering air is the job of an air filter.