Which cylinder has two working ports and can extend or retract by supplying hydraulic fluid to either port?

• A. Single-acting cylinder
• B. Double-acting cylinder
• C. Poppet valves
• D. Contamination

Answer: (B)

A double-acting cylinder has two working ports, allowing motion in both directions. Supplying hydraulic fluid to the end on one side of the piston pushes it to extend, while supplying to the opposite end pushes it to retract. This bidirectional actuation is why it can extend or retract by choosing which port is energized. By contrast, a single-acting cylinder uses only one port for movement in one direction and relies on a spring or external force to return. Poppet valves are just a type of valve, and contamination refers to dirt in the system; neither describes the bidirectional actuation of a cylinder.