Re: Ohm's Laws

Again, the impracticability of achieving a constant-current
source is emphasized by considering what happens to the
voltage across the output as the load impedance is increased
toward an open circuit. it approaches infinity. So a true
constant-current source implies an infinite voltage source
with an infinite source resistance.

The impracticability of achieving a constant-voltage
source is emphasized by considering what happens to the
current at the output as the load impedance is decreased
toward a short circuit. It approaches infinity. So a true
constant-voltage source implies an infinite current source
with a zero source resistance.

This is what we call a model.

Practically, mains circuits are considered constant voltage.

It means that you can consider (dependent on design) a certain piece of
equipment operating with the same properties as your model. However, there
is a point when the real circuit behaviour parts from the model behaviour.
This is where the validity of your model ends.

Exactly the same is true for current sources.

It
is, of course, impossible to have a *true* constant voltage
source. And you are explaining why mains circuits have fuses or
breakers.

No. I explained that every model is valid within its defined limits. Outside
those limits the model is completely useless (usually another model takes
over or an extension of the previous model is required).

Best regards,
Igor


.

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