I can afford it 😉. At one time I was going to put it back together and ask Dr. Weiss if he could find a good place to lay it on the LIGO during a science run. He is desperate to get rid of that nasty 1/f.
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I've known some ta's here reprimanded/given poor positions for only having negative feedback. In that case though it was more that they didn't do their job well, but there was a general concern by us teaching staff over only getting negative feedback, even if it was constructive.
That's why I choose not to give any at all, I don't know how it's going to be used and when it was made clear to me that useful negative feedback would most likely be misunderstood or deliberately misinterpreted, I didn't want any part in it. I suspect it's used for statistical purposes too, and there should be better ways anyway of determining performance other than asking students what they thought
Yes, it's sadly more of a popularity contest than it is necessarily a useful evaluation of how well the teaching staff did their job. When you get a bunch of negative feedback because you teach a weed-out class that everyone hates and your evaluations only reflect that the students are unhappy with the class (and their terrible performance, if I'm utterly honest) and say nothing about the TA contribution, then it just kinda sucks. The staff at my last uni at least knew more or less which classes were the unpopular ones and accounted for it. Anyways, this has little to do with teaching people how to problem solve and is one of those "how do we actually evaluate how well someone teaches?" topics.
In any case, I don't envy Zung having to teach an older crowd, at least my students were still in school mode. 😀
In any case, I don't envy Zung having to teach an older crowd, at least my students were still in school mode. 😀
Of course I knew.. Should I have not answered it? Should I have railed on about near superconductivity?
Were you shocked that I simply answered?
There was no mathematics involved. It was simple field theory, what typically happens when electrons travel through a conductor.
At least you think so and claim so. Never has there been any consistent explanation, nor are there any actual tests on them which can be demonstrated as proof. They're hawked as devices that can choose between good electrons and bad..
But again, that is not what Max asked..
jn
The fact that you claim they work means you claim that some energy states are good and some are bad, and that the device can select the good energy states from the bad ones.
This is basic logic, John..
jn
And, of course, a clear decision to again hawk the units on this thread..
@jneutron & PMA,
i´ve posted in the past some measurements from a german publication (unfortunately no translation available) that at least had one measurement result that wasn´t compatible with the assertion that those mentioned devices were just resistors.
I´ll post it again and maybe you are able to replicate what happened?
i´ve posted in the past some measurements from a german publication (unfortunately no translation available) that at least had one measurement result that wasn´t compatible with the assertion that those mentioned devices were just resistors.
I´ll post it again and maybe you are able to replicate what happened?
There is such a thing, and albeit it is more often called motional impedance, I think 'back-emf impedance' is also quite understandable. (There are some things Joe has grasped.)jneutron said:
It can be calculated Z = BlV/I and it forms just the resonance peak in every driver's impedance graph.
That'd be nice. Hopefully, there will be enough information that will allow me to totally destroy the measurement technique, analysis, and conclusions, as well as claim that their familial heritage is questionable and they have stinky armpits.....😀
If it doesn't have enough information, it may not be of any use. Well, ok, without the armpits.
Testable and verifiable is a requisite..
jn
Please post it and we/I shall see what can be done. Deutsche sprache would be OK.
The proper term should be used.
Back EMF is a created voltage in response to movement within a magnetic field..
Impedance is the relationship between voltage and current. It is equationally related to the drive voltage/frequency, the emf of the vc, and the losses in the system.
A simple example...
If I short an aluminum former, IOW a former without a gap, it will fight the motion within the gap. However, it will not generate a voltage on the voice coil.
It will however, cause a change in the electrical impedance seen at the terminals, as it will require more current for the same velocity.
The same occurs due to a shorting ring.
It is very important to include the stuff that not 90 degrees out of phase with the drive voltage.
Sometimes it may be considered semantics, but we are driving far deeper into the speaker model and energy relationships (well, I am), and we cannot afford be so carelessly glib with terminology.
jn
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Well, we have 3 sorts of impedances in the electroacoustic transducer model. Electrical (V/I), mechanical (F/v) and acoustical (p/w) impedances. Via transformer we transfer acoustical impedance to mechanical side and then via gyrator from mechanical to electrical side. That's how we get the electrical substitutional schematics 😉
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