Air pump

An air pump moves air into or out of a vessel, creating pressure differences that enable evacuation, inflation, or gas transfer.

Vacuum pump: A pump that removes gas from a sealed volume to create a partial vacuum. This is the air pump’s specific form when its purpose is evacuating a vessel.
Otto von Guericke: A German scientist and engineer who built an early effective air pump in the seventeenth century. His pump enabled experiments that made atmospheric pressure dramatically demonstrable.
Bicycle pump: A hand-operated pump that compresses air to inflate bicycle tires. It illustrates air transfer into a vessel against rising pressure.
Pressure: Pressure is force exerted per unit area by a fluid or other material. A pump creates the pressure differences that drive air into or out of vessels.
Air compressor: A machine that raises air pressure and delivers compressed air. It emphasizes pressurizing and storing air, unlike pumps used chiefly to evacuate vessels.
Positive-displacement pump: A pump that moves fluid by repeatedly trapping and displacing fixed volumes. Many hand-operated air pumps move gas by trapping and displacing successive volumes.
Magdeburg hemispheres: Two metal hemispheres that resisted separation after air was evacuated from their joined interior. The famous demonstration used von Guericke’s pump to display the force of atmospheric pressure.
Vacuum cleaner: An appliance that uses a pressure difference to draw air and debris through an intake. Its motor-driven fan acts as an air-moving pump rather than evacuating a sealed vessel.
Atmospheric pressure: The pressure exerted by the weight and motion of the atmosphere. It limits how far an ordinary pump can lower pressure in an evacuated vessel.
Ejector: A device that uses a fast-moving fluid jet to entrain and transport another fluid. It can evacuate gas without a mechanically driven pumping chamber.

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