What is the function of a solenoid valve?

A solenoid valve serves a critical role in pneumatic systems by using an electric current to control the opening and closing of air flow paths. When an electric current is applied to the solenoid, it creates a magnetic field that either opens or closes the valve, allowing or restricting the flow of compressed air. This function is essential for automating the control of air flow in various applications, such as in machinery or other automated systems.

The ability to remotely operate the valve via an electric signal enhances system efficiency and flexibility because it allows for precise control without manual intervention. This is particularly important in applications that require fast or frequent changes in air flow direction or pressure.

In contrast, the other options do not accurately reflect the primary function of a solenoid valve. Manual control of air flow is not the role of a solenoid valve, as it is designed for automated operation. Regulating pressure is primarily managed by pressure regulators, not by solenoid valves, although they can influence pressure indirectly through flow control. Cooling down the system isn't a function associated with solenoid valves; that's typically handled by cooling systems or heat exchangers. Thus, option C clearly identifies the vital role of solenoid valves in pneumatic systems.