What is the difference between a battery and a capacitor? — Kyle, New York, N.Y.
A battery is a can full of chemicals and metals. The can could contain something as simple as lemon juice along with a copper strip and a zinc strip, although modern batteries tend to be a bit more sophisticated than that. An electrochemical reaction produces voltage and current. If the reaction is reversible, you have a rechargeable battery. If not you have a disposable battery.
A capacitor is a can full of thin metal sheets held very close together but separated by an insulator. You pump electrons in to charge up the plates, and then the capacitor can pump electrons out again to power a circuit.
As a general rule:
1) You can charge and discharge a capacitor much more quickly than you can a battery. The chemical reactions in a battery take time.
2) A capacitor doesn’t really “wear out”, while a battery does.
3) Capacitors are much larger than a battery that stores equivalent charge.