Final answer:
Valves are devices that control the flow of fluids in a specific direction, preventing backflow. They are used in different systems, including plumbing and the circulatory system. Valves ensure fluid moves forward and do not flow backward.
Step-by-step explanation:
Valves are devices that regulate the flow of fluids, such as gases or liquids, in a specific direction. They are commonly used in various systems, including plumbing, the circulatory system, and industrial processes. The purpose of installing valves is to control the direction of flow and prevent backflow. Valves are designed to open and close in one direction, allowing the fluid to move forward while blocking its return. For example, in the circulatory system, there are valves in the heart that ensure blood flows in one direction. Similarly, in plumbing systems, valves prevent the water from flowing backward.