How does an elevator work?

Inside the shaft, steel ropes run from the top of the car, up over a grooved wheel called a sheave, and down to a counterweight that typically equals the car plus about forty percent of its rated load. An electric motor turns the sheave, and friction between rope and groove drags the ropes along, which is why these are called traction elevators. Because the counterweight balances most of the mass, the motor works against only the imbalance, not the whole car. Guide rails bolted to the shaft walls keep the car from swinging. Hydraulic elevators use a different approach entirely, pushing the car up on a fluid-driven piston, and are common in low buildings of a few floors where a machine room at the top makes little sense.

The deeper principle is that lifting is expensive but balancing is cheap. Raising a loaded car by one storey takes real energy, yet if an equal mass descends at the same time, the two exchange potential energy and the motor supplies only the shortfall. On the way down with a heavy load, a modern drive can even push current back into the building's supply. The second principle is that safety must not depend on the rope. Elisha Otis solved this in 1852 with a mechanism that clamped the car to its rails when rope tension went slack, and demonstrated it in 1854 at the New York Crystal Palace by having the rope cut while he stood on the platform. Today a governor rope spinning too fast trips the same idea.

Modern elevators spend more of their intelligence on scheduling than on lifting. Destination dispatch systems ask passengers for their floor in the lobby and group them into cars going to nearby stops, which cuts the number of intermediate halts and moves more people with the same hardware. Gearless permanent-magnet machines are compact enough to sit in the shaft itself, freeing the rooftop machine room. Flat steel-reinforced belts have replaced round ropes in many systems because they bend around smaller sheaves. In the tallest buildings, rope weight becomes a limit on how far one car can travel, so towers stack separate rises and shuttle passengers between sky lobbies rather than running a single shaft top to bottom.

Common misconceptions cluster around danger and speed. People believe a cut cable sends the car plummeting, but the car hangs from multiple independent ropes and mechanical safeties grip the rails if it overspeeds. People believe the door close button always works, when in many installations it is disabled during normal service and takes effect only in independent or fire service modes. People believe pressing the call button repeatedly speeds arrival, but the controller registers one call and ignores the rest. People believe an elevator in freefall could be survived by jumping at the last instant, which is wrong on the physics and irrelevant in practice, since freefall is what the entire safety design exists to prevent.