Quadcopters are a popular type of drone with four propellers. Each propeller is driven by a spinning motor. The motors are connected to an on-board battery by an electrical circuit. When the propellers spin, they generate lift, the force that pushes the drone up. In order for the drone to remain in the air or fly upward, the lift must be greater than or equal to the drone’s weight, the force that pulls it down toward the Earth. Drones can also steer by making the propellers spin at different speeds.