capacitor
/ kuh-PASS-ih-ter /
Think of two metal plates facing each other with a thin gap between them, hooked to a battery. The battery pumps electrons onto one plate and pulls them off the other, so one plate ends up negative and the other positive. They can't touch, so the charge just sits there, held in place by its own attraction across the gap. That patient store of charge is a capacitor.
A capacitor stores energy not in moving charge but in the electric field that fills the gap between its plates. How much charge it holds for a given voltage is its capacitance, and that grows with bigger plates, a smaller gap, and a good dielectric stuffed into the gap. The dielectric polarizes and weakens the field, which lets even more charge crowd onto the plates before the voltage limit is reached.
This matters because capacitors are everywhere — smoothing power supplies, timing circuits, storing the brief jolt for a camera flash, and forming the memory cells that hold a computer's data. A common misconception is that a capacitor is like a battery; it isn't. A battery makes energy from slow chemistry and holds a lot of it, while a capacitor stores far less but can release it in an instant — speed, not capacity, is its gift.
A camera flash works by slowly charging a capacitor over a second or two, then dumping all that stored energy into the bulb in a few thousandths of a second. The slow build-up and sudden release — that brilliant burst of light — is a capacitor showing off exactly what it does best.
A camera flash stores charge slowly in a capacitor, then releases it in an instant.
A capacitor and a battery both store energy, but a battery makes it from chemistry and holds far more, while a capacitor holds less yet delivers it almost instantly.