Final answer:
The slide valve and piston in the reversing valve is actuated by pressure in the hydraulic line. Hydraulic systems apply this principle, allowing small forces applied to one piston to exert larger forces on another due to pressure transmission through the fluid. This facilitates the lifting or moving of loads and can be seen in hydraulic presses and control valve operations.
Step-by-step explanation:
The slide valve and piston in the reversing valve is actuated by pressure directed through the hydraulic line. In such systems, depicted in various figures, a force applied to one piston results in pressure disseminated throughout the fluid, that, in turn, affects another piston. This is the principle behind hydraulic systems and presses, where force and pressure are transmitted unaltered through an encased liquid medium, be it oil or another type of hydraulic fluid. This allows for actions such as the lifting or moving of heavy loads with relatively little input force, utilizing the mechanical advantage generated by the differences in piston surface areas.
For instance, the hydraulic press, which operates by applying a small force to a small piston, consequently produces a larger force on a larger piston, causing it to move and exert substantial pressure. This action is utilized across various engineering applications, including the operation of control valves and reverse osmosis systems, where back pressure is applied to reverse the normal direction of fluid flow through membranes.