This video shows the working principles of a hydraulic jack with animations. Hydraulic jack uses the Principle of levers and Principle of Pascals law to transfer and multiply the small force applied by humans, which is necessary for lifting heavy loads like cars and trucks.
A hydraulic jack uses a liquid, which is incompressible, that is forced into a cylinder by a pump plunger. Oil is used since it is self lubricating and stable.
When the plunger pulls back, it draws oil out of the reservoir through a suction check valve into the pump chamber. When the plunger moves forward, it pushes the oil through a discharge check valve into the cylinder.
The suction valve ball is within the chamber and opens with each draw of the plunger. The discharge valve ball is outside the chamber and opens when the oil is pushed into the cylinder. At this point the suction ball within the chamber is forced shut and oil pressure builds in the cylinder./via/read more: wikipedia