Which system utilizes liquids for power transfer?

The hydraulic system is characterized by its use of liquids to transfer power, making it distinct from the other systems listed. In a hydraulic system, hydraulic fluid is pressurized to create motion and force, which can be utilized in various applications such as hydraulic lifts, brakes, and heavy machinery.

This method of power transfer is particularly advantageous because liquids are incompressible, allowing for precise control and the ability to transmit force over distances without significant loss of energy. Thus, hydraulic systems are widely used in industries where heavy lifting or precise control is necessary, such as in construction equipment, automotive systems, and manufacturing processes.

In contrast, pneumatic systems rely on gases for power transfer, mechanical systems involve solid components and physical movements, and electrical systems depend on the flow of electricity. Each of these systems has unique applications and characteristics, but none utilize liquids in the way hydraulic systems do.