Final answer:
A DC alternator typically contains six diodes that convert AC output into DC current for use in a vehicle's electrical system.
Step-by-step explanation:
A DC alternator typically contains six diodes. These diodes are used to convert the AC output from the alternator into DC current that can be used by the electrical system of a vehicle. Each diode functions as a one-way valve, allowing current to flow in only one direction. This conversion process is necessary because the alternator's rotor generates alternating current, which needs to be converted to direct current for use in a vehicle's electrical system.