Hydraulic Terms Motor a device that converts fluid power into a mechanical power. It usually provides torque and rotary motion to a shaft. Pump a device that causes a liquid to flow against a pressure. It converts mechanical energy into fluid energy. Viscosity a measure of the internal friction or the resistance to flow of a fluid. Filter a device through which fluid is passed to separate matter held in suspension. Heat exchanger-a device that transfers heat through a conducting wall from one fluid to another