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= Capacitor
{wiki}
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:
$$
I(t) = C \dv{V(t)}{t}
$$
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 behaviour 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>.
\Image[https://upload.wikimedia.org/wikipedia/commons/7/73/IEEE_315_Fundamental_Items_Symbols_%2832%29.svg]
\Video[https://www.youtube.com/watch?v=4PkcOeZCE0g]
{title=Finding Capacitance with an Oscilloscope by Jacob Watts (2020)}
{description=Good experiment.}
```