Oh dear me
I'm hoping this is a difference of perspective, otherwise we have the idiot v's the flux, and that leaves me not just down the hole. but at the very far end of the hole... so here I go.
I was trying to avoid dealing with the emf in the coils, as I felt it added ideas which did not need to be introduced. I was trying to describe increase in rpm giving an increase in power.
The original question was ""At this point in time the charging current is 2Amps. What happens to the current if the RPM increases to 1000? The battery should still clamp the voltage down to 12V and the generators internal resistance is constant ... the amps should not change or do they? I figure that something has to give but am not quite grasping it.""
soooo.....
I had defined the E as the battery voltage ie :
"Yes the batt voltage will remain essentially the same (use this as an assumption not real, but for this case we will assume it remains the same) so assume E= constant"
I didn't want to involve the induced voltage in the coils, as it is not necessary to understand it in order to measure the Watts out. I have assumed E= terminal voltage, as if we measure I out and terminal voltage(in this case defined as E), we can calculate power at a given rpm.
By assuming E=constant, we no longer needed to look at its potential variance(coil EMF), but rather the measurable under load value....which we nailed as fixed for this discussion.
I fixed R because I wanted to simplify the model. I didn't want to introduce inductance and a host of other possible contributors to the discussion, as their relevancy to it ceased to exist once we defined R as fixed for this purpose ie:
"Yes the internal resistance will remain roughly the same (not worrying about temp at this stage) so assume for now R= constant"
So given the assumptions that were laid down, working E out of the equation was the best way of avoiding having to discuss forcing volts etc, which in the end don't matter to the alternator user, (yes they matter to the alternator maker for sure), he seemed primarily concerned with output changes corresponding with rpm input changes. This by necessity would seem to dictate that we deal with what is directly measured at the output.
then there was:
""There is no voltage divider as you pondered up above, So If we have to keep the voltage constant..............hmmm""
It's here that I think I made it confusing...
"" If you think of the start point as that where the alternator voltage is the same as the battery I=0 E= batt. As we speed up and increase the power, E stays the same..... how's this?""
Here E was defined as Battery volts, not EMF in the coil, and fixed it's value at E=batt.
So this still works I think
"If W=IxE and E=IxR then W=Ix(IxR) so as we increase the power (W), and R is treated as a constant, then the I must increase. so the power can increase even without worrying what happened with the E."
this avoids having to talk about how the alternator works, but instead shows how to explain what we measure at the output, and that we don't have to agonise over what happened in the coils, what happened with the voltage, or how it got there.
I don't think this absolves my sins completley, but hopefully shows where I thought I was coming from.
One feels a rouge asteroid could come my way soon
...........oztules