I'm mainly interested in technical discussions and understanding the point of view of others regarding this experiment. I believe I have a good grasp of this experiment and I do not yet buy into the assertion that professor Lewin et al are promoting, but I am also trying to understand why others see something different than I do.
To that end....
One of the points about voltage drop sticks in my mind. I'll try to explain it in my current foggy mind state (it has been a long day).
Using the generalized KVL to produce the result of zero requires the addition of voltage drops across inductors. It is easy and common to think this is realistic but in reality...
It doesn't make sense. Mind you... I find Lewin's explanation of the measured voltage drop interesting but don't quite think it is completely correct.(The thing where the actual voltage drop being measured is of the meter input circuit not the drop across the inductor.)
Using our favorite spring analogy, voltage drop across an inductor makes even less sense.
If you apply a compression force to the free end of a spring, the other end secured in position, the spring compresses and stores the energy being applied.
At any point in time during the compression the force applied to the free end is equal to the force applied by the spring to the securing surface at the other end. (not talking about breaking the sound barrier when compressing the spring
)
In other words, the voltage difference between the ends of an inductor is zero. There is no voltage drop across an inductor. The force isn't delayed from one end of the inductor to the other.
Of course, this isn't always true but I'm talking about this situation. 'Single Pulse and not considering wire resistance'
So, KVL being what it is - a law about electric fields - does not apply to an inductor. There is no electric field across an inductor.
So what did the wires do? They were voltage sources during the pulse induction. The simulation would be more correct if you replaced the wires with batteries (for that couple of milliseconds). The problem with that is they would each be required to produce 1/2V.
The reason I say that is the total voltage dropped across the resistors is 1.0V.
The reason I say that is KVL is an electric field only law. It cannot be applied in it's original form due to the wires becoming transformer secondaries - due to Faraday's laws.
So what law could be used without mangling it for ease of obtaining results while using completely incorrect methods and not espousing obfuscation nor eschewing elucidation of what is really happening? (Cough, Cough, gag!)
Faraday's.
The problem is some will still be stuck on the odd looking results. I'm referring to the -.1 + .9 volts. or the voltage drop across the resistors. That adds up to .8V
Using Faraday the wires become voltage sources. This means their sine changes. Granted, since 'time' is now part of the equation due to induction things become unclear for many.
Just like KVL has become.
You can simplify the problem by rearranging the circuit. You can do that. This is a series circuit. Put the two voltage sources together. They add up to 1V. Put the resistors in series together. They add up to 1V..... Yes, they do.
Another fine point no longer clarified... simple measured potential is the measured difference between 2 points. The difference between -.1V and +.9V is 1 Volt. The voltage sources add up to 1 Volt. Since sources and loads are algebraically added with opposite sine... The result is zero Volts. I don't really care because Kirchhoff didn't use the word 'zero', or the German equivalent.
It all still works but is harder to obtain. (Even when doing it verbally and not exactly correct according to Faraday) At least the hard way means better understanding of what really is going on. This understanding includes things like:
...Zero potential is BS. It is only a reference point to hang your brain on. Like kissin' cousins say, "Its all relative"
...When an unaccounted for variable jumps in it is time to apply a law that includes that variable, not time to 'adjust' the one you understand. Just because the result is correct doesn't mean the method was.
...a current loop can take the same path it would through a loop of wire - even if you replace that loop of wire with the negative equivalent - a sheet of copper with slots for the resistors.
...Rise and fall times do matter
One point is...
Applying some mangled form of a perfectly good law may get the correct results but it doesn't help folks understand what is actually happening. One result might be somebody using the reliable and correct spring analogy one moment and then.... contradicting the same idea the next.
Not picking on anyone in particular. I'm guilty of exactly the same thing.
I'll admit to not being precise but the point was to get the point across and give .99 some reference for my opinions on this subject.
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Topic: Professor Walter Lewin's Non-conservative Fields Experiment (Read 312193 times)
