How an Alternator Works

"Now to power the vehicle of course once the vehicle is started, the current must alternate. You have what is called an alternator and it converts alternating current to direct current. Every automotive industry vehicle in North America uses direct current. The alternator converts alternating current to direct current which supplies 12.5 volts to the entire electrical system. Over here we have another box with relays in it. Some circuits exceed the fuse rating and they need more supply. What it does is it converts low current through the relays into high current to supply circuits to the power accessories inside the vehicle."