What is the purpose of a solenoid valve in a pneumatic or hydraulic system?

• A. To regulate energy in the fluid
• B. To electrically control fluid flow by actuating a valve
• C. To filter contaminants
• D. To measure pressure

Answer: (B)

A solenoid valve turns an electrical signal into fluid-path control. The coil in the valve creates an electromagnetic field when current flows, moving a valve element (like a spool or diaphragm) to open one passage and close another. This directs compressed air or hydraulic fluid to the desired path, or vents it, enabling automated, remote, or rapid actuation of actuators such as cylinders. It’s about switching where the fluid goes based on an electrical input, not about filtering, measuring, or regulating the fluid.