Alkaline battery

An alkaline battery is the familiar AA or AAA cell. It makes about 1.5 volts as zinc gives up electrons that flow through your device to manganese dioxide, and it stores far more energy than the older zinc-carbon cells it replaced.

It is built inside a steel can, usually nickel plated, that serves as the positive terminal. First a ring-shaped cathode of manganese dioxide powder mixed with graphite is pressed against the inside wall. The graphite matters, because manganese dioxide alone conducts poorly. A paper-like separator lines the ring. The middle is filled with a gel of fine zinc powder soaked in potassium hydroxide solution, the electrolyte that carries charged particles between the two sides. A brass pin, like a nail, is pushed into the zinc gel to collect current and is attached to the negative end cap, with a plastic seal that has a built-in safety vent.

In use, zinc is oxidized and manganese dioxide reduced until one runs out. The alkaline cell was developed by Lewis Urry at Eveready in the late 1950s. In the remote control, two of them last a long time because the remote draws power only for moments at a time.