[Lonesome in Massachussets]

The torque on the alternator's shaft varies with load. When you aren't drawing current from it, the torque is caused solely by bearing friction.

When you draw current from it, the flow of current induces a torque on shaft which requires more fuel to keep the engine turning at the same speed. The change in (torque x rotation rate) = the change in (RMS Voltage x RMS Current).

Try an experiment. Sit in an old (1964) Volkswagen with the engine at a low idle and turn on headlights. You can audibly hear the pitch of the engine change.

[calex59]

Try an experiment. Sit in an old (1964) Volkswagen with the engine at a low idle and turn on headlights. You can audibly hear the pitch of the engine change.

Or just turn the air conditioning on in any car with 4 cylinder engine and see what happens, even driving down the road you will feel the power drop and have to compensate by pushing down on the accelerator, which is why you get less gas mileage(regardless of engine size)with an air conditioner on than when it is off.

[Rick.Donaldson]

Thanks. I know this too.