If the load on an actuator changes, what happens to the pressure required to move the load?

• A. It stays the same
• B. It also changes
• C. It doubles
• D. It becomes zero

Answer: (B)

In pneumatics, the pressure needed to move a load depends on the resisting force the load presents. The actuator’s piston generates force equal to pressure times piston area (F = P × A). To start or continue motion, this force must meet or exceed the load plus any friction. So when the load changes, the necessary pressure changes as well. If the load increases, you need more pressure (proportional to the load, assuming the area stays the same). If the load decreases, you need less pressure. For a given piston area, the relationship is P = F / A, so pressure is not fixed but varies with the load. The other options aren’t correct because pressure isn’t constant, it doesn’t automatically double every time, and it isn’t zero just because the load changes. For example, with a 1 in² piston, moving a 20 lb load needs about 20 psi; doubling the load to 40 lb would require about 40 psi.