[Part Name] Brush and spring [Description] Used to transmit power to motor [Manufacturing] The Brush was made using molding and the spring was made by drawing copper into the shape of a spring [Reason for Using Materials] carbon is used because it can conduct electricity in its most famous allotrope, graphite which is a very efficient conductor of electricity. [Forces Applied] The springs apply force to hold the brushes in place. [Functional/Cosmetic] This part is purely functional as it powers the armature as well Materials: Carbon(graphite) and copper [Quantity] 2 [Complexity] 3 [Reason for Shape] 
The brushes are semi circular rings to effectively allow the armature to move between them.