Right. Be prepared to become enlightened.
Right. Be prepared to become enlightened.Since you rejected my baby-stepped method for guiding you to enlightenment, I'll be forced to reveal the shocking truth to you. The conservation of energy holds for when Kirchhoff fails because the energy the resistor is dissipating comes from the fuh...., the fuh-fieh..., the fie... No, I can't. I can't put you through this emotional sacrifice. I have scruples.
Again you show that you can't even read
I did not ask to tell where energy comes from. I ask you to show law of conservation of electrical energy using Maxwell's equations. Apparently you are afraid of what comes next after you do it.
Since you don't want to know where the energy comes from, it'll be impossible for you to understand it using Maxwell's equations, or whatever.
This was exactly my point. It doesn't make sense to talk about a voltage source as purely being an impedance.
A voltage source is NOT an impedance, much less "purely". Read Feynman lectures volume II chapter 22.
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What determining the equivalent circuit of a battery has to do with measuring an impedance in an AC circuit under a varying magnetic field?
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So what causes the change in their behavior is the _ _ _ _ _.
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As you confirm, not only the secondary doesn't behave like an inductor (there's no 90 degree phase shift), but also it is not even an impedance: because the voltage on the secondary is a function of something external to itself, which is in fact the _ _ _ _ _ generated by the current in the primary.
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How can this be, once the primary is connected to a voltage source?
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So now not even the primary can be identified as an inductor anymore.
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Forbidden? Why? It perfectly demonstrates what I said before: if you don't understand the underlying physics of electromagnetism you'll be limited in your ability to design and analyze circuits.
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If you read your own words again you'll see that you've already answered your question.
Today at 08:42:17 am » Insert Quote
You are ignoring this user.
Do not confuse public forum with private chat, tell for those who you think will understand.
To cut the crap: KVL is based on conservation of the charge which is based on law of conservation of energy.
As soon as you write energy_generated_inthe_loop = energy_dissipated_inthe_resistor equation, KVL can be derived from it.
Energy conservation in electromagnetism is a little bit more complicated, and can be derived, as in the case of conservation of charge, from the modified (by Maxwell) Ampère's law, however you need to understand that the energy that's powering the resistor is not coming from a component in the circuit.
Let's start with charge conservation, which is easier for a circuit-head guy like you to understand. You can find it demonstrated here.
In the picture below you can see how KCL fails, but charge conservation holds.
The sum of currents going in and coming out of the volume represented by the closed dashed line to the left is different from zero, violating KCL. But conservation of charge holds because the excess charge is being stored in the body inside the volume.
I dont see how charge is conserved inside the dotted circle. Curent is charge divided by time anyway.
I dont see how charge is conserved inside the dotted circle.
Curent is charge divided by time anyway.
But yeah i can see what the point is, an example of KVL not holding. We KNOW that KVL is not a law of physics.
It holds in most cases but not all,
QuoteBut yeah i can see what the point is, an example of KVL not holding. We KNOW that KVL is not a law of physics.
Kirchhoff studied carefully the behavior of currents and voltages in circuits and published the results of his findings in the "Annals of Physics". Then he derived his theorems, as he called them, from those empirical data. His discovery was a major breakthrough.
So KVL and KCL ARE laws of physics. But a law of physics has not to work under whatever condition. As important as it is to understand KVL and KCL it is to know when they hold and when they fail.QuoteIt holds in most cases but not all,
I would say that KVL and KCL do NOT hold most of the times. Where can you find a place on earth where you don't have varying electromagnetic fields? The thing is that we PRETEND that KVL and KCL hold by approximation. We stash fields inside capacitors and inductors, we create ground planes, employ shielded conductors, we decouple lines, inductors, capacitances, all to avoid having to deal with fields. And when we have to deal with them, we employ rules of thumb and equivalent approximate models.
And what we cannot tame and make to conform to KVL/KCL we call "parasitics".
This creates the illusion that KVL and KCL hold "in most cases". But it's only an illusion. Not that we will abandon this illusion all of a sudden. We need to know what it means, and not to try to linger to it if it clearly shows that we will be limited in our ability to interpret the phenomena around us.
As important as it is to understand KVL and KCL it is to know when they hold and when they fail.
I would say that KVL and KCL do NOT hold most of the times. Where can you find a place on earth where you don't have varying electromagnetic fields? The thing is that we PRETEND that KVL and KCL hold by approximation. We stash fields inside capacitors and inductors, we create ground planes, employ shielded conductors, we decouple lines, inductors, capacitances, all to avoid having to deal with fields. And when we have to deal with them, we employ rules of thumb and equivalent approximate models.
And what we cannot tame and make to conform to KVL/KCL we call "parasitics".
As I said before, scientific populism is going to be a big problem a few yeas ahead.
It's just next fallacy of yours. Those two round objects on the left together form charged capacitor and wire between them - load where energy that is stored in the capacitor, dissipates. KCL holds.
Wird ein System von Dräten, die auf eine ganz beliebige Weise mit einander verbunden sind, von galvanischen Strömen durchflossen, so ist:
1) wenn die Drähte 1, 2, ...µ in einem Punkte zusammenstoßen,
I1 + I2 + ...+Iµ = 0,
wo, I1, I2, ... die Intensitäten der Ströme bezeichnen, die jene Drähte durchfließen, alle nach dem Berührungspunkte zu als positiv gerechnet;
So why do we still use Maxwells equations if they are wrong according to Quantum electrodynamics? Its much like the reason why we still use Kirchhoffs circuit laws despite being wrong according to Maxwell.
On a macroscopic level and under certain conditions these laws still work just fine, while being much more convenient to work with when you want to actually calculate them with actual numbers. The 3 sets of laws are basically just different abstraction layers for electricity. Just chose the desired abstraction level and be aware of its known limitations.
Tho to be honest there is very very little reason to go any deeper than Maxwells level of abstraction for engineering use.
I dont see how charge is conserved inside the dotted circle. Curent is charge divided by time anyway.
He most likely did mean that charge is distributed evenly between two round objects. Yes, it is so - if there is separate point of reference (ground?) to measure voltages/charges of both round objects. In such case we have two capacitor paradox which again agrees with KVL.
We have just one wire, with just one current.
This problem is analogous to the KVL problem: we have just one voltage, and no other to balance it that can be directly measured in the circuit.
It's just next fallacy of yours. Those two round objects on the left together form charged capacitor and wire between them - load where energy that is stored in the capacitor, dissipates. KCL holds.
In case you insist that there is just one wire and just one current meaning no path for return current - then I say that you don't even have circuit, thus Kirchoff's Circuit Law do not apply. There is huge difference between "do not apply" and "do not hold".
so those two round objects together indeed is capacitor, C=q/V.
QuoteAnd I always thought, the EMF is defined as the tangential force per unit charge in the wire integrated over length, once around the complete circuit/loop! But not at all, it was hiding in the resistor and my voltmeter!
You clearly thought wrong, I regret. EMFs will never "hide" inside (static) wires (considered as ideal, that is).
Let's examine KCL in the words of Kirchhoff himself:QuoteWird ein System von Dräten, die auf eine ganz beliebige Weise mit einander verbunden sind, von galvanischen Strömen durchflossen, so ist:
1) wenn die Drähte 1, 2, ...µ in einem Punkte zusammenstoßen,
I1 + I2 + ...+Iµ = 0,
wo, I1, I2, ... die Intensitäten der Ströme bezeichnen, die jene Drähte durchfließen, alle nach dem Berührungspunkte zu als positiv gerechnet;
Translation
Let a system of wires, which are connnected with each other in an entirely arbitrary way, be traversed by galvanic currents [i.e. DC], then:
1) if the wires 1, 2, ...µ meet at one point,
I1 + I2 + ...+Iµ = 0,
where, I1, I2, ... designate the intensities of the currents, which flow through each wire, all calculated as positive in the direction of the point of contact;
We have just one wire, with just one current. This problem is analogous to the KVL problem: we have just one voltage, and no other to balance it that can be directly measured in the circuit.
QuoteAnd I always thought, the EMF is defined as the tangential force per unit charge in the wire integrated over length, once around the complete circuit/loop! But not at all, it was hiding in the resistor and my voltmeter!
You clearly thought wrong, I regret. EMFs will never "hide" inside (static) wires (considered as ideal, that is).Sorry, my wording was wrong, I should have said ‘I always believed, the EMF...’.!
Because the clearly wrong ‘thought’ is from Feynman Volume II chapter 16 Induced Currents.
As you say, electromag is so unintuitive, so much bullshit around.... you can’t even trust books anymore.
This phenomena is well known in literature as the ‘One-Wire-Single Current-Sophism”.
For sure, can only be solved with Maxwell equations
Maybe you missed the point, the ‘connection point’ (Berührungspunkt)?
Hence, a single wire hitting the connection point is a dead end, hence I1 = 0 .
Yes exactly my point that a voltage source is not an impedance.
In that chapter 22 that you mention it clearly shows that induced voltage acts like a voltage source. So including the induced voltage when calculating impedance of a component is just as nonsense as directly calculating the impedance of a voltage source using the voltage across its terminals.
2 terminal components can't have multiple impedance at the same moment in time.
is there any reason why you replaced the world field with underscores?
Its not exactly a secret that magnetic fields are what makes inductors work.
Exactly it doesn't behave like an inductor anymore, but instead behaves like a coupled inductor.
But it doesn't mean its inductance simply disappeared. The same magnetizing current is still needed to hold up the field, but because the two inductors are sharing the same flux means they can also share the magnetizing current. Since the resistor on the secondary can't provide a source of reactive current means that all the magnetizing current comes from the voltage source on the primary. The resistive load does however cause a in phase current that makes a opposing field in the secondary that affects the field in the primary, where it induces voltage according to Faradays law. Since there is a voltage source forcing a well defined voltage across the primary, this instead draws extra current to correct this field. This extra in phase current is what drags the total current back away from lagging 90 degrees. As for the secondary, it has no need for out of phase current, because all of its magnetizing current is provided by the primary.
So the inductance didn't go anywhere. The effect of inductance is simply buried under the other currents.
So yeah, sorry i still don't see the exact circumstance when a piece of wire stops being an inductor. Or does becoming a coupled inductor not count as being inductive? If so please explain why.
So why do we still use Maxwells equations if they are wrong according to Quantum electrodynamics? Its much like the reason why we still use Kirchhoffs circuit laws despite being wrong according to Maxwell.
Kirchhoff's laws are not wrong according to Maxwell. Maxwell's equations do not only confirm that KVL and KCL are right, but also state in WHAT CONDITION they are right.
The source of the errors is elsewhere.
QuoteOn a macroscopic level and under certain conditions these laws still work just fine, while being much more convenient to work with when you want to actually calculate them with actual numbers. The 3 sets of laws are basically just different abstraction layers for electricity. Just chose the desired abstraction level and be aware of its known limitations.
A cat is a special case of mammal, and the description of a mammal is an abstraction of a cat (and every other mammal, as a matter of fact).
QED is an abstraction of Maxwell's equations, as Maxwell's equations are abstractions of KVL/KCL.
KVL/KCL are a special case of Maxwell's equations, as Maxwell's equations are special cases of QED.
KVL/KCL are NOT abstractions of Maxwell's equations by the simple fact that they don't work for all the cases for which Maxwell's equations do.
This is another illusion. Because we ram KVL/KCL down the throats of our circuits and close our eyes to the errors due to this approximation (and we manage to get away with it in many cases) we have the impression that KVL/KCL are just simplified (hence abstracted) cases of Maxwell's equations. But this mindset will bite you in the butt sooner or later. You need to be always aware of the limitations of KCL/KVL and, if the error due to approximating Maxwell to Kirchhoff is gross enough, resort to what will give you the most accurate prediction.
QuoteTho to be honest there is very very little reason to go any deeper than Maxwells level of abstraction for engineering use.I think the inventors of the transistor would not agree with you, but anyway...