Batteries come in many different sizes. Some of the tiniest power small devices like hearing aids. Slightly larger ones go into watches and calculators. Still larger ones run flashlights, laptops and vehicles. Some, such as those used in smartphones, are specially designed to fit into only one specific device. Others, like AAA. Capacitors can serve a variety of functions. In a circuit, they can block the flow of direct current(a one-directional flow of electrons) but allow alternating current to pass. (Alternating. In recent years, engineers have come up with a component called a supercapacitor. It's not merely some capacitor that is really, really good. Rather, it's sort of some hybridof capacitor. A battery can store thousands of times more energy than a capacitor having the same volume. Batteries also can supply that energy in a steady, dependable stream. But sometimes.
