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

@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.

@thor Think of it in terms of speed-of-light delay.. an electron can know what is terminating the far end (a resistor, open, short) until the electron (or rather the 3wave of energy through the electrons) physically gets to that point, and then transmitts that information back to the feedpoint somehow.

So any wire **must** act like a wire capable of conducting and identical to any other wire regardless of what lies at the far end... at least as long as the speed of light would take to go both ways. After that then things can change...

@thor yea for electronic components they are a bit pricey.. but nothing you cant afford in a prototype or two. Just may not be the cheapest for mass production is all.

@thor If your simplification were true then an empty capacitor wouldnt momentarily act as a short circuit when power is first applied.

@thor Most opamps are designed for operations well below RF frequencies.. but there are high-frequency op-amps and we use them all the time.

@thor picturing it as waves sloshing back and forth is entierly accurate.

In fact in early computers memory (on the order of bits) was done via physical delay lines where 1s and 0s were represented as waves in a pool of mercury. If the ends of the tank werent perfectly calibrated to match it youd get reflections and your data would degrade.

Can you imagine being the guy with the screw driver who was like "Oh shit my computer broke again, gotta readjust the sprints in my liquid tank of mercury based memory"

@thor Op amps are used all the time.

Attached is an RF design that goes up to UHF frequencies that I did that has 3 op-amps int he design all for different purposes.

https://qoto.org/@freemo/104793170211640131

@thor Yup, its how we discovered most of the critical math to make RF possible.

They even thought they could fix it with higher voltages, idiots just burnt the line up.