Capacitor by Ciro Santilli 37 Updated 2025-07-16
The fundamental intuition about capacitors is that they never let electrons through.
They can only absorb electrons up to a certain point, but then the pushback becomes too strong, and current stops.
Therefore, they cannot conduct direct current long term.
For alternating current however, things are different, because in alternating current, electrons are just jiggling back and forward a little bit around a center point. So you can send alternating current power across a capacitor.
The key equation that relates Voltage to electric current in the capacitor is:
So if a voltage Heavyside step function is applied what happens is:
  • the capacitor fills up instantly with an infinite current
  • the current then stops instantly
More realistically, one may consider the behavior or the series RC circuit to see what happens without infinities when a capacitor is involved as in the step response of the series RC circuit.
Figure 1.
Electronic symbol of a capacitor
. Source.
Video 1.
Finding capacitance with an oscilloscope by Jacob Watts (2020)
Source. Good experiment.
Video 2.
Capacitors Explained by The Engineering Mindset
. Source. 2019.
LC circuit by Ciro Santilli 37 Updated 2025-07-16
When Ciro Santilli was studying electronics at the University of São Paulo, the courses, which were heavily inspired from the USA 50's were obsessed by this one! Thinking about it, it is kind of a cool thing though.
Video 1.
Tutorial on LC resonant circuits by w2aew (2012)
Source.
Video 2.
LC circuit dampened oscillations on an oscilloscope by Queuerious Guy (2014)
Source. Finally a video that shows the oscillations without a driving AC source. The dude just move wires around on his breadboard manually, first charging the capacitor and then closing the LC circuit, and is able to see damped oscillations on the oscilloscope.
Video 3.
Introduction to LC Oscillators by USAF (1974)
Source.
Video 4.
LC circuit by Eugene Khutoryansky (2016)
Source. Exactly what you would expect from an Eugene Khutoryansky video. The key insight is that the inductor resists to changes in current. So when current is zero, it slows down the current. And when current is high, it tries to keep it going, which recharges the other side of the capacitor.
Video 1.
Transmission Electron Microscope by LD SEF (2019)
Source. Images some gold nanopraticles 5-10 nm. You can also get crystallographic information directly on the same machine.
University by Ciro Santilli 37 Updated 2025-09-09
One major issue is that teachers don't have the right incentive to, nor are selected to, teach well. Thus the existence of Rate My Professors! But we can do better...
Which is why Ciro Santilli wants to destroy its current format with OurBigBook.com. He believes that we can find a more efficient organization to achieve both the social and research functions of university, by first doing as much as possible online
Cover up the entire sky in a compatible way with the traditional constellations. They are also very square, the boundaries consisting only of vertical and horizontal lines on the sphere.

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