Disc Brake Work on Principle of Friction when Driving person Press the Brake Pedal, The Hydraulic Brake Fluid forces to master cylinder from Brake Lines to the Caliper. The Pressure Generated on Piston in Brake Caliper then pushes to Brake Pad Against the Brake Rotor The Large amount of heat is Generated due to friction Brake Rotor slowly Stopping the Vehicle. In Hybrid Electric vehicle Energy Stored in Battery while Braking in called HEV.