Numerous models electric motors work based on the use of excuses, but there are many models of engines that works without the presence of this piece. It is very important, but it has as the engine in the absence thereof, provided that it is constructed for this purpose.
If you do not know what it is for the electric motor brushes understand that she will transmit the electrical contact of a fixed part to a sliding part. This is the great feature of most schools are present in any type of machine, and would be different with the electric motor.
As we know the engine is responsible for making the transformation of electrical energy into mechanical energy quickly and economically. In order to do this transformation the engine needs to pieces that make up its operation, but as it is one of those pieces and with it the engine can exercise its functionality.