What generally differentiates hydraulic systems from pneumatic systems?

Hydraulic systems and pneumatic systems are both used for transmitting power through fluid mediums, but they differ fundamentally in the types of fluids they use and their applications.

Pneumatic systems specifically use compressed air or gas to transmit power. This involves the use of air that is often released or exhausted back into the environment after performing work, such as activating a pneumatic device or tool. This distinction is significant because the behavior of gases (like air) under pressure differs from liquids, which is what hydraulic systems utilize.

On the other hand, hydraulic systems operate using a pressurized fluid, generally oil. The incompressibility of liquids allows hydraulic systems to maintain consistent pressure and control, which is ideal for lifting heavy loads and providing strong, precise motion. Thus, while both systems can perform work, the material they use (air for pneumatics and liquid for hydraulics) results in very different characteristics in terms of load capacity and systems design.

The other choices do not accurately reflect the fundamental differences between these two types of systems. Therefore, the answer highlights an essential aspect of pneumatic systems, emphasizing their reliance on air and the mechanism by which they operate.