When equal pressure exists on both sides of a standard cylinder, what is the effect described in the material?

• A. do nothing
• B. extend
• C. piston leakage
• D. retract

Answer: (C)

When equal pressure exists on both sides of a cylinder, there is no net force to move the piston, so it does not extend or retract. The material describes the resulting effect as piston leakage, which reflects that even with balanced pressures, imperfect seals can allow a small amount of fluid to pass the piston packing. In other words, movement requires a pressure difference, but leakage can still occur through the seals independent of that movement. So the observed phenomenon under balanced pressures is leakage past the piston seals rather than motion of the piston.