http://copaseticflows.appspot.com/hamtest Explains a direct digital synthesizer and the questions related to it on the amateur radio, (ham radio), extra class exam in the United States. Used by free practice exams at http://copaseticflows.appspot.com/hamtest
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http://copaseticflows.appspot.com/hamtest Brief overview of the practice exam website.
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How to determine the phase between voltage and current on the extra class exam without a calculator.
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http://copaseticflows.appspot.com/hamtest In polar coordinates, what is the impedance of a network consisting of a 100-ohm-reactance inductor in series with a 100-ohm resistor?
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Here's what you'll see. As the field between the magnet poles is increased, the cylindrical superconductor which must have frozen in a bit of residual field when it was cooled will first orient it's magnetic moment perpendicular to the field to minimize the torque it feels. As the field strength is increased, the superconductor will then begin to move itself out of the magnet altogether eventually swinging off the screen. You'll also catch the odd snippet of extraneous lab conversations.
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A YBCO superconductor is placed between the poles of a very uniform magnet and then cooled into its superconducting state. The field frozen into the sample at the state transition opposes the fringing fields on the magnet. However, had the magnetic field been strong enough to quench the superconductor, the results would have been the pendulum swinging freely beyond the pole pieces' diameter.
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This is for my notes. It rambles, it rolls, and it even has a few mistakes. You've been warned.
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I hadn't seen that matrix multiplies are really just dot products until last week.
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A short high level explanation of the hole theory of superconductivity followed by a brief outline or our planned experiment.
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Playing around with the superconductors on my last day in the lab. The superconductor was field cooled, (a fancy way of saying the permanent magnet was placed on top of the superconductor before liquid nitrogen was added.) The flux from the magnet penetrated the superconductor while it was in the normal state and was frozen in place once it entered the superconducting state. The result was that the superconductor behaves like a permanent magnet.
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