Source: https://mokxi.com/parts/capacitor Updated: 2026-09-28 Part # Capacitor The one part that integrates over time, so an RC circuit really charges. or see every part - 2 pins - 1 property Drawn live by the editor's own code, at the size you see it. Reference ## Every one of its 2 pins Pin What it does 1 Either plate. 2 The other plate. This part ## What it does A capacitor is the one part on the bench that genuinely integrates over time rather than answering instantly. It joins whatever else is on its nets into a shared analog solve, and the matrix works out the whole island together, which is what lets an RC network land on the true exponential curve rather than an approximation of one. Charging or discharging toward a fixed voltage through a fixed resistance, the result is exact for any time step, however large; what changes with the step size is only how finely a moving source is tracked in between. That is the part behind a 555’s timing, an RC debounce filter, and any circuit on this site where something changes gradually instead of switching instantly. It is still a simple model: there is no leakage, no equivalent series inductance, and no dielectric behavior beyond a small series resistance, only the charge and discharge curve itself, done properly. Reference ## The one property you can set Property Default What it means value 10 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. How it is modeled ## What is true about the Capacitor, here ### What is modeled 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. ### Not modeled 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. From Capacitor, in full. Projects ## See the Capacitor in a project Learn ## Where it turns up in a lesson ### In the twelve week course - Week 4: Timing without a processor: the 555 - Week 9: Pulse width modulation and the eye ### In a learn article - The 555 Astable: Timed by a Capacitor, Not a Crystal - Blink an LED with a 555 Timer, No Microcontroller - Measure It: Read a Circuit With a Scope and Plotter - The RC Time Constant, on an Oscilloscope - PWM to an Analog Voltage With an RC Filter - The 555 Monostable: One Press, One Timed Pulse - Multisim Live Is Gone: A Chromebook Alternative - 555 Timer Projects for a Science Fair (No Coding) - Online SPICE Simulator: Run and Export Netlists More parts ## The rest of the bench Every one of these is drawn and simulated the same way. Full-size breadboard A real 0.1 inch grid with the rails and the center channel, 63 columns wide. Jumper wires Drag from any pin or hole to any other. Corners snap, and you can drag them. Power A supply rail at the voltage you choose. Ground The other end of every circuit. LED Lights when current flows. Five colors, and the brightness is what your eye would see. Resistor Any value you like, with the color bands drawn to match. ESP32-C3-DevKitM-1 A RISC-V board that runs your firmware at 160 MHz on the real memory map. Pushbutton A 12 mm tactile switch. Hold it while the simulation runs. Raspberry Pi Pico The RP2040 board on our own Cortex-M0+ core. Pick a program and press Run. Raspberry Pi Pico W Raspberry Pi Pico W (RP2040). The same board and the same pinout as a Pico, with the CYW43439 on it. The WiFi is simulated (no radio, no real internet), and the on-board LED, which hangs off that chip rather than off GP25, is driven through the same path. Everything else is the Pico. STM32F411 Black Pill The Black Pill on our own Cortex-M4 core. Pick a program and press Run. BBC micro:bit V2 The nRF52833 board with its 5x5 LED matrix, buttons A and B and a speaker. Wire the rings to a breadboard. See every part ## Wire up the Capacitor Open the editor and push it into the breadboard. It is free, and it runs on your own machine. Start building Open the editor