Starter operation

Both the generator and the starter have brushes as a mechanical means of changing electrical current polarity and subsequentally the polarity of the magnetic field created.

Both the genny and starter use the magic of magnetism to create electrical power. Magnetism is created when a direct current (battery) flows thru an electrical coil which magnetfies an ironcore. As the ironcore magnet is attracted to the electrical magnetic field, it causes the motor armature to turn.

Both the starter and the generator have multiple electrical magnetic coils, each coil is connected to a corresponding set of copper buss-bar switch contacts called an armature which the spring-loaded brushes make electrical contact.

The changing coil magnetism makes the rotating generator generate DIRECT CURRENT which is necessary to charge a BATTERY. The changing coil magnetism makes the starter armature rotate as it chases the magnetic pole which keeps changing because the starter motor is rotating..... ...respectfully, Dell

The brushes are made of a mysterious combination of copper and graphite, for both conductivity and low wear on the commutator.

Alternators have smaller brushes than generators, and usually last longer because Alt brushes carry only the field current. Genny brushes carry the output current, which is higher, more arcing, more heat, etc....

Perhaps Dell can say it a little better, but that's how I tell 'em at nite school.

Good Luck
Jim Cox