🎓 Dr. Freemo 🇳🇱 @freemo@social.cleverlibre.org

@thor sims are always going to be limited wrt their real world equivelant.

@thor So they are equivelant only in the idealized world.. in the real world you have parasitics and other concerns... so in the real world you may have a reason to prefer one over the other, but its mainly for reasons you shouldnt worry about right now.

@thor Here is a post I wrote a few years ago explaining circuit duals, I have a whole section on capacitor-inductor... I wrote it for people who have 0 EE knowledge so you should have no trouble following it start to finish (The very end gets a little advanced):

https://drive.google.com/file/d/1fECh_IeFYBHoFuaw08zO2dkluZPunkP7/view?usp=sharing

thats because you have more than one kind of dualism in circuits... you have parallel-series dualism, and you have capacitor-inductor dualism... there are other kinds too like magnetic-eletric dualism.

@thor Im sure if you ran through the math it would start to make much more sense... even the equations for the two are identical just inverted.

@thor inductors are exactly the same as capacitors except everything is switched... it responds to current the same way a capacitor responds to voltage.. an inductor at 90 degrees to a capacitor is functionally equivalent to the capacitor.

They also both can store similar amounts of energy, and are both "slow" in regards to voltage or current, etc.

@thor a turbine or impeller... basically imagine a pipe with a propeller inside the pipe itself. It has weight so the propeller has momentum. If you turn off the flow of water from the pump the propellers momentum will cause it to continue to spin for a while thus causing the water to continue to flow after the pump is turned off.

@thor im not sure what the best analogy for the programming world would be... very different beast.

@thor For sure, it helps if you think of it like water in a pipe.. voltage is pressure, current is rate of flow. A capacitor is like a huge storage tank filled from the bottom, and inductor is like a weighted fan in the flow of water.

@thor every property of an inductor has a dual property in a capactor.

Inductors do not allow current to change abruptly, therefore if you have a current running through them and turn it off, the current will continue to flow at its old rate, but now it needs to cross a high-resistance airgap, so the voltage spikes to thousands or millions of volts to keep the current where it was, at least momentarily.

Capacitors have a dual of this, for capacitors it wont let voltage change abruptly. So if a capacitor is charged and you short it out then it wants to keep the voltage the same, the only way it can do this is to provide a massive current flow (because the short has a small non-zero resistance)...

So yea you get the equivelant in both, in one case it will create huge voltages to maintain its state, the other will create huge currents to maintain its state.

@thor inductors are a fundemental component.. they are important to learn even if you dont intend to use them much, just to understand the EE theory better.

@thor capacitors can do high pass or lowpass... a highpass filter with a capacitor is a lowpass filter if you swap the coil for the capacitor in place... also vice versa..

@thor A inductor at 90 degrees to the capacitor is identical to the capacitor.. so why the capacitor? (answer int he audio world is the inductors would tend to be too large).

@thor I wrote a very long paper explaining circuit duals, ill send it to you if you want.

A dual is a functionaly equivelant circuit that undergoes some transform.. in this case replacing capacitors with inductors.

@thor coils are rare in audio circuits for several reasons, not the least of which being that they would have to be too large to be of any use.. but in theory they are perfectly equivelant, despite not being practical.

@thor You can think of them that way... what we say is "The voltage across a capacitor must change smoothly", in other words, it must be differentiable (it cant jump from one voltage to another without crossing the voltages inbetween.

An inductor, being the capacitors dual, has a similar rule "The current through an inductor can not change abruptly".

@thor an inductor is just the dual of a capacitor... any circuit you make with capacitors can have an identically functioning circuit with inductors instead of the capacitors (to do so you simply need to create the circuit dual under capacitor-inductor transform)

@thor yes they can be used as low pass or high pass filters, but that is thinking int he frequency domain. Thats great, but wont help you in terms of understanding how it behaves moment to moment in the signal domain.

@thor You can not use a idealized model with a fixed current source and a capacitor, as the voltage would increase towards infinity.

You will have a better time of thinking of voltage sources with capaitors and current sources with inductors.

But the important take away here is when you turn on any circuit to charge a capacitor in some way in the moment the circuit is first turned on capacitors act like short circuits.. likewise inductors act like open circuits.