BRONCO351 i noticed you have a Duralast battery.drive up to AutoZ--- ask them to do a load test to make sure the other parts are operating up to par.It's free.

 

The ripple occurs over a period of time (yes, it's a VERY short period), but the VOLTAGE being measured is still the same electrical potential (pressure) as always. The fact that it's bouncing up & down and fading away over time doesn't change the physical phenomenon of voltage. It's still just "voltage".
Look at what you wrote: you're using "alternating current" and its definition to define "alternating voltage"... Have you ever seen anything that says it's powered by "120AV", or do they all say "120VAC"? I know that voltage can change in a circuit over time, but it's not as significant as the change in current, so it's not a term that's used.
Not all AC is the result of a change in voltage. In fact, your example of the functioning of a dynamo (conductor moving within a magnetic field) proves that. The change in current isn't a result of a change in potential (voltage); it's a result of the changing magnetic flux, which induces current in the conductor. In this case, the electrons aren't moving as current initially; they're being moved because they're in the conductor that's moving relative to the magnetic field. Since the field strength (flux) changes with position, the effect of the flux on the electrons changes, causing current to flow. But it's not by voltage - it's by the phenomenon of EMI. This is a case of current being induced by the movement of charged particles within a solid moving mass (the wire) under the influence of magnetic flux. It's the same way that a transformer works, but in that application, only the magnetic field moves. In a brush-type motor, the magnets are fixed, and the current is moved to a different conductor (winding) as the armature rotates by the brushes & the commutator. All of them (dynamo/generator/alternator, transformer, & motor) work on the principle of inductance, with voltage being an EFFECT rather than a CAUSE.

 

ok guys .. to much information for me ..But do you think a bigger batt will help ..yes or no

 

First, ensure that the battery is charged to ~12V with the engine off. Then test the battery voltage (on the POSTS, not the wire terminals) while you're cranking - if it's below ~10V, the battery is weak. I recommend the MotorCraft Silver Series that you can see in my sig link.

 

Check the secondary voltage of a transformer with only the source hooked up...=alternating voltage

Current is the effect, and is always proportional to voltage.

I suppose we can only agree to disagree, which isn't really a bad thing!

Wayne