Mechanical or hydraulic devices that regulate speed of a machine are called?

Governors are mechanical or hydraulic devices designed specifically to regulate the speed of machines. They function by automatically adjusting the input or output of a machine based on its speed, ensuring that the machine operates within a set range. This is particularly important in engines and turbines, where maintaining a consistent operating speed is crucial for efficiency and safety.

Governors can adjust fuel supply, throttle position, or other parameters to respond to changes in load, thus keeping the speed of the machine stable. This ability makes them vital components in many applications, including automotive and industrial machinery, where precise speed control is necessary for optimal performance.

Other options, while related to machine operation, do not specifically serve the function of speed regulation. Clutches are primarily used to connect and disconnect power transmission, brakes are meant for stopping or slowing down motion, and gearboxes mainly change the torque and speed of rotation without directly regulating it.