semantics question, generator or alternator Options

[type47]

So, I went to local FLAPS to have my "alternator" tested (it tested good) and they asked me if it was a generator (since it was so old) or an alternator. I said alternator. I looked it up in the PET because the guy testing it needed the part number (022.903.023 is -4) and the PET says it's a generator. What shall I call it and would that have any influence on the testing. Someone might explain the difference btw alt and gen. (gen doesn't need external current for the field windings, if I recall...)

[Tom]

Well,
there is a lot of misunderstanding in this thread.
Our alternators only produce about 14-17 volts AC- not 120. A full wave bridge is used to convert the AC to DC. A full wave bridge is about 90% efficient so there is more AC voltage to the bridge than DC out. 14 AC to bridge is 12.6 DC out.
All generators do not use permanent magnets. Small ones mostly do, IE, bicycle type, and the early auto ones.
Generators may produce AC or DC, depending on the way they are constructed.
Basically for automobile use a generator is used to provide DC to charge the battery and an alternator is used for the same purpose. An alternator can produce more power out at a lower RPM due to it's 3 phase windings.
Tom