What component of a pump transmits energy in the form of velocity to the water?

The impeller is the component of a pump that is specifically designed to transfer energy to the water, converting mechanical energy into kinetic energy. As the impeller rotates, it imparts velocity to the liquid, creating flow. This increase in velocity is essential for the effective operation of the pump, as it enables the liquid to move through the system and reach its intended destination.

The design of the impeller, including the shape and size of its blades, plays a crucial role in determining the efficiency and pressure of the water being pumped. By converting the rotational energy from the pump shaft into fluid energy, the impeller is central to the pump's function, making it the correct choice for this question.

In contrast, while the pump shaft plays a vital role in providing the necessary mechanical energy from the motor to the impeller, it does not directly transmit energy to the water itself. The casing serves to contain and direct the flow of water but does not impart velocity. The throttle valve is used to control the flow rate and pressure of the liquid but does not function as a source of energy transfer to the fluid. Thus, the impeller stands out as the key component responsible for increasing the water's velocity in the pumping process.