Capacitor

A real capacitor, solved by the matrix rather than approximated part by part.

Wherever a capacitor sits, it pulls every net it touches into an analog island: the matrix solves it together with whatever else shares those nets, which is why an RC network here lands on the true exponential curve rather than a rough guess.

Pins

Pin	What it does
1	Either plate.
2	The other plate.

Properties

value: capacitance, in the unit the parts bin uses (microfarads). 10 is a typical decoupling or timing value; a 555 astable commonly uses 1 to 100.

What the model gets right

The capacitor declares itself to the kernel as analog and then does nothing else at all. It reads its own voltage, V(1) - V(2), straight back off the solved nets for the probe. That is what lets an RC timing network land on the exponential to a tenth of a percent, and what puts a 555 timer's astable within 0.05% of the textbook formula, because the timing genuinely comes from the RC network and not from a rounded-off approximation of it.

What it does not model

It is not an ideal capacitor: there is 0.1 ohm of series resistance in it, which the analog island needs to stay well-posed. That is smaller than any real electrolytic's ESR and smaller than a wire, so it changes nothing a lesson measures, but it is there and it is not zero.

Every capacitor starts discharged. The operating point solved at power-on puts 0 V across every capacitor in the circuit, so a circuit is never resumed part-way charged.

No leakage, no dielectric absorption, no voltage or temperature coefficient, no self-resonance, and no polarity enforcement: an electrolytic-style value wired backwards behaves exactly as it does the right way around, where a real one would vent.

Common mistakes

Leaving one side floating and expecting the capacitor to charge anyway. With either terminal in the air there is no loop for current to flow around, so the capacitor holds whatever charge it has and drives neither pin. It needs both plates in a real circuit path, the same as it does on the bench.

See it in action

RC filter on the scope and 555 blinker both use a capacitor as the actual timing element, not a decoration. See them at /templates.

The RC time constant page charges a 100 nF capacitor through 10 k on the scope, and PWM to an analog voltage uses a 10 uF one to turn an Uno's PWM into a steady voltage.