# Tag Info

1

Assuming it's not deliberate, two things come to mind: light-sensitive switches will have significant hysteresis to avoid flickering on and off in dim light. So they will require brighter light to switch on in the morning than to switch off in the evvening. human vision perceives a given light level as being brighter during a transition from dark to ...

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If we measure the voltage between the terminals of a diode in an open circuit, the outcome is zero. The E-field of the junction in only internal. When a forward voltage is applied, but there is also a big resistance in series in the circuit, there is a tension between the ends of the diode but below 0.7V. Even below the threshold a small current flows. When ...

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A diode in its grounded state is an insulator. Start with that. The way we build the diode is, we take two insulators that are very close to being conductors but not quite there, and we make them conductors, in one case by inserting atoms which have extra electrons to give (N-doping) and in the other case by inserting atoms which have a tendency to instead ...

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Now, when a voltage is applied in the right direction, free electrons flow to the part where the holes are. This happens independently of an external voltage, because the electrons in the n-doped part feel the urge to fill the holes in the p-doped part. But because electrons move from the n-doped part to the p-doped part, the n-doped part becomes positively ...

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I also think the effect is cogging. This torque is position dependent and its periodicity per revolution depends on the number of magnetic poles and the number of teeth on the stator. Cogging torque is an undesirable component for the operation of such a motor. It is especially prominent at lower speeds, with the symptom of jerkiness. Cogging torque results ...

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Hi Reading this is interesting. The reason that the fan goes backwards is simple. It is a Direct Current motor which has a capacitor across the power terminals to keep the power factor near to unity. A motor is a wound component which will produce a lagging current so a capacitor is added to bring that current nearer to unity (A capacitor creates leading ...

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I think by "simple" you mean Linear, which would consist of Source, R/L/C, and Transformers. Or as Engineers tend to label them "Electrical Circuits" as opposed to "Electronic Circuits" which have transistors/diodes. These circuits can have their responses written in terms of Linear ODEs. The definitions get tricky, because as ...

4

Did the fan really rotate backwards, or merely appear to? You may be looking at a Wagon-Wheel Effect. Basically, when a wheel or propeller rotates at a certain speed, particularly if you're using fluorescent lighting, which has a natural flicker to it that isn't always obvious, the object can appear to stop or rotate in the opposite direction. All the ...

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How do i calculate output resistance if i have the corresponding table for it? There are two output resistances here: 1)total AC, and 2)differential (dynamic) output resistances. The second one causes the incremental variation of the first. AC output resistance is the total instantaneous resistance for a given output voltage Vcb. Althu this is the parallel ...

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On balance, I think @nielsneilsen's answer is likely the correct one. But there is another possibility. Is there a control loop in play? Almost universally, practical control systems for hitting a desired position, velocity, flow rate or whatever use a PID control loop, sometimes omitting the P or D element depending on the application. Other control ...

142

The overshoot behavior you noticed is called cogging and occurs when the magnet arrangement in the motor "catches" the rotating magnetic core of the motor during shutdown and jerks it back to one of the local strong spots in the field. You can demonstrate this yourself by carefully rotating the fan blade around with your finger when the motor is ...

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I just have guesses. Is there any sort of spring in the motor, or anything spring like? For example a fan belt could stretch if it was trying to turn a stiff bearing. You might discover this by trying to spin the fan by hand and seeing if it turns the other way when it stops. Another source of springiness could be electrical. A power smooths variations in ...

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Your PC is a box with limited vents for air to enter/exit. Especially if these clog up with dust, the fan could create a noticeable pressure differential between inside and outside of the box. After the fan turns off, that equalizes, forcing some air backward through the fan, and causing it to rotate backward. Maybe. Another possibly, as pointed out in ...

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Here is the most basic answer with regards to why we use ultrasound for imaging rather than sound in the human range of hearing. Ultrasound, by nature, is high frequency. The higher the frequency, the denser the sound traveling through the medium, which, in turn, provides a higher resolution image. You could certainly create an image using sound waves ...

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This is kind of like asking "how hot is too hot?" It will depend on how fast a battery can be charged and discharged- weakest link. You can always connect through a resistor, let it sit for some time so they equalize (current through resistor drops to zero or voltage across resistor becomes zero), then connect directly. Practically it doesn't have ...

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I interpret the question as being about cooling. In a thought experiment you may scale up the A64FX ARM CPU powering FUGAKU by a linear factor of 10.000 or 100.000 and then replace its integrated solid state electronic components by discrete ones. Cooling will not be a theoretical problem as the device is essentially 2D and you have the third dimension to ...

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Ohmic would mean means it follows Ohm's law $\ I= {\mathcal{E} \over R}$ It's non-ohmic so it does not, the current passed is not proportional to the EMF. Symmetric would mean that for negative EMF the the exact opposite current would flow. Being asymmetic, (in this case) it means that current flows more readily in one direction than in the opposite ...

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If "switches and wires" means transistors, then yes, you could build a supercomputer out of individual transistors instead of microchips. The Atlas was an early supercomputer from 1962 built from germanium transistors. Although it was considered a supercomputer at the time, it was very slow by modern standards. It performed 700,000 instructions per ...

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