What component of the hydraulic jack assembly raises and lowers the elevator car?

The correct answer is the piston. In a hydraulic jack assembly, the piston is a crucial component that moves within the cylinder. When hydraulic fluid is pumped into the cylinder, it creates pressure that pushes the piston upward, which in turn raises the elevator car. Conversely, when the fluid is released from the cylinder, the piston moves down, lowering the car.

The cylinder serves as the housing for the piston and contains the hydraulic fluid, but it does not perform the action of raising or lowering the load. The plunger is typically used in different mechanisms and does not function the same way as a piston in hydraulic systems. The head usually refers to the top part of the assembly where connections might take place and does not have a direct role in the raising and lowering action of the elevator car.