The capacitor, explained simply
A capacitor stores electrical energy as charge. Learn how it works, how to read its value and what it does in an Arduino circuit.
How does it work?
Two conductive plates separated by an insulator (the dielectric). When a voltage is applied, charge builds up on the plates. The capacitor charges, then can give that energy back. Capacitance is measured in farads (F), in practice µF, nF or pF.
Charging and time constant
Through a resistor R, a capacitor C reaches 63% of the voltage in τ = R × C, and about 99% in 5τ. Example: 10 kΩ and 100 µF give τ = 1 s.
Common types
Ceramic (pF to a few µF, non-polarised, decoupling); electrolytic (1 µF to several mF, polarised: the short leg is −); film (audio, precision). The code "104" on a ceramic means 10 × 10⁴ pF = 100 nF.
What is it used for?
Decoupling a microcontroller's supply (100 nF next to each chip), smoothing a rectified voltage, debouncing a button, creating a delay or an RC filter.
Build an RC circuit in the simulator and watch the charging curve on the oscilloscope.
Try it freeFAQ
Can a capacitor explode?
Yes, an electrolytic fitted backwards or above its rated voltage can bulge or burst. Pick a rating at least 1.5 times the circuit voltage.
Does it pass DC current?
No, once charged it blocks DC but passes changes (AC). That's why it works as a filter.