What device is responsible for turning the sheave that lifts and lowers the elevator car?

The elevator machine is crucial in the functioning of an elevator system. It is the device that provides the necessary power to turn the sheave, which is a pulley over which the elevator's cable runs. This mechanism allows the elevator to lift and lower the car in response to user commands.

The elevator machine often includes an electric motor, gear reduction for torque and speed management, and controls for smooth operation. When a command is given from the control panel, the elevator machine activates, causing the sheave to rotate and subsequently moving the elevator car up or down. This process is integral to the vertical transportation system in buildings, allowing for safe and efficient movement between floors.

Other options like the control panel, elevator pit, and buffer serve different functions. The control panel manages user input and operational commands, the elevator pit houses essential components and provides a space for the elevator car to rest at the lowest level, and the buffer acts as a safety feature to absorb impacts at the bottom of travel. Each of these components is important for overall elevator operation, but it is the elevator machine that directly accomplishes the physical lifting and lowering of the car.