If the carbon brushes of an electric motor are damaged, the motor cannot start.

Carbon brushes are conductors that connect the rotor and are devices used to transmit energy or signals between the fixed and rotating parts of electric motors, generators, or other rotating machinery. They are typically made from pure carbon and binders, and their appearance is usually square, held in a metal bracket, with a spring inside that presses them against the rotating shaft. When the motor rotates, electrical energy is transmitted to the coil through a commutator.

Carbon brushes, also known as electric brushes, are sliding contact components widely used in many electrical devices. Because their main component is carbon, they are called carbon brushes. They are subject to wear and tear and should be regularly maintained, replaced, and cleaned of accumulated carbon. The main function of carbon brushes is to conduct electricity while rubbing against metal. Unlike metal-on-metal friction and conduction, where friction may increase and connections may weld together, carbon brushes do not because carbon and metal are two different elements. Most of their applications are in electric motors, and they come in various shapes, such as square and round, etc.