Recent content by DaveE

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    What would it take to convince you of magic / supernatural

    The thing that I almost never hear when people talk about this is the fallibility of our own minds. We are full of cognitive biases (i.e. "Thinking Fast an Slow" - D. Kahneman). We also have sensory deficits, like optical illusions and such. Anything you suggest could be a hallucination or the...
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    Current density in a wire that is being used to charge a capacitor

    Q(t) is the total charge on the capacitor, including what has accumulated in the past. The current in the wire is the rate at which new charge is added/removed.
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    I Resistivity of a conductor

    When there are more collisions, the charges have a shorter mean free path so they don't accumulate as much energy before they collide again. So, more collisions, but less energy in the colliding charges.
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    Are Back EMF, Reverse Current, Reverse Saturation current, and Backfeeding the same?

    No. Could you ask a more specific question? These terms cover a wide range of subjects in EE as I interpret them; Motors/Magnetics, Semiconductors, Power Distribution... It just too hard to describe everything in one post.
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    The Bear Facts

    Also stupid hunters. They shoot the deer, then walk up to it thinking it's dead. The deer gets up and attacks. https://www.bbc.com/news/world-us-canada-50180755
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    How does a pulsed plasma thruster work?

    Also collisions with the outward moving electrons will push some of the plasma. The charged ions will also feel E and B field forces, like the electrons.
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    B Visit to Hayden Planaterium -- The projector is gone?

    I would guess that you could do a better job with a computer and some lasers now. I'm not sure the hardware is the problem with the content you saw.
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    What is wrong with this picture?

    Yup, just like what might happen when they try to open that gate.
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    How does a pulsed plasma thruster work?

    A short, hand wavy, description: When the arc forms, hopefully on the right side near the teflon, it creates the B field (out of the page). Then the moving electrons (up) experience the force you described ##\vec F=q \dot {\vec r}\times \vec B## (to the right). So that arc is propelled to the...
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    Receiver Circuit Question -- What role does this antenna capacitor play?

    "the earthy end..." Perfect, LOL. Because we all know "earth" is seldom really earth. I'd never heard that before, I hope it wasn't a typo. It's pretty much guaranteed that I'll steal this sometime.
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    The Bear Facts

    LOL. In my day of backpacking near Yosemite, we had a similar rule about hanging up your food in the trees. You didn't have to hang it up well enough to keep the bears from getting it, in fact that was often impossible, but you did have to hang it up better than the other backpackers did. That...
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    I dt without f(t)?

    Yes, I agree their notation sucks. In dynamic systems (control systems) it is common to leave the range out, with an assumption it's "all relevant history". This is because most of the interest is in the behavior (stability, etc.), not the actual operating points. One of the cheats you get from...
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    Difficulty with machining bismuth, any suggestions/tips/other ideas?

    I was thinking EDM. But, really, this is way above my pay grade. Maybe you should call these guys and ask them: https://www.thomasnet.com/profile/00453035/vulcan-global-manufacturing-solutions.html?cov=NA&what=High+Purity+Bismuth&heading=5291356&cid=453035&searchpos=7
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    I Which kind of function is this?

    I'd vote for some 3-D fractal, like this one maybe: edit: I guess this isn't a function though. More like an algorithm. Functions can't be multi-valued, right? Plus maybe you mean 4-D; "a function of x,y,z". Anyway, I like the pictures.
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