How Hydraulic Brakes work?

      The working of hydraulic brakes is based on the principle of Pascal law. These brakes are used in automobiles. It consists of a tube which contains oil called brake oil. One end of the tube is fitted with a piston working in a master cylinder. There are in all four tubes through which the master cylinder is joined to four small cylinders (each containing a piston of large area) one for each wheel of the automobile. These small cylinders are called brake cylinders. When the brake pedal is pressed by applying a force, the piston in the master cylinder begins to move inside the tube and exerts pressure on the oil. This  pressure is transmitted to the oil in the brake cylinder. The undiminished transmitted pressure pushes the piston in brake cylinder which acts as a brake shoe attached to a caliper. The resulting friction stops the wheel. When the pressure on the pedal is released, the spring which connects the two brake-shoes contracts and pulls them off from the rotor. Thus the wheel is again free to rotate.