Hydraulic devices multiply force through the principle of Pascal's Law, which states that pressure applied to an enclosed fluid is transmitted undiminished to every point in the fluid.

Here's how it works in a simplified way:

1. Fluid Incompressibility: Hydraulic systems use an incompressible fluid (usually oil) that can't be squeezed into a smaller volume.

2. Pressure Transmission: When a force is applied to a small piston in a hydraulic system, it creates pressure in the fluid. This pressure is transmitted equally throughout the fluid.

3. Area Difference: The fluid pressure acts on a larger piston at the other end of the system. Since the pressure is equal everywhere in the fluid, the force on the larger piston is greater because it has a larger surface area.

Here's a formula to illustrate:

* Force (F) = Pressure (P) x Area (A)

If the area of the larger piston is 10 times greater than the area of the smaller piston, the force output on the larger piston will be 10 times greater than the force input on the smaller piston, despite the pressure being the same throughout the system.

Example:

* If you apply a force of 10 Newtons to a small piston with an area of 1 square centimeter, you create a pressure of 10 Newtons per square centimeter.

* If the larger piston has an area of 10 square centimeters, the force exerted on it will be 100 Newtons (10 Newtons/cm² x 10 cm² = 100 Newtons).

Therefore, hydraulic devices multiply force by transferring pressure from a smaller area to a larger area, effectively increasing the force output.