Yesterday the thought occurred to me that I don’t really know how a battery works. Whatever goes on inside that little cylinder is a mystery to me. Now that I know the secret, it seems even more amazing!
First , let me get the words right. A battery is actually defined as a set of individual things that work in unison. So when we say “battery”, we’re talking about a collection of Galvanic cells. (also called Voltaic cells) Let’s examine a single cell to see what’s really going on in there.
The goal of a cell is to create a flow of electricity. Looking at this from the atomic perspective, imagine the individual atoms all lined up in a length of wire. When the electricity flows, it’s not the atoms that are traveling, but the electrons (the tiny bits that orbit around the nucleus) that are getting passed from one atom to the next like a hot potato. This is called electron flow, and it’s what makes your lights turn on.
A galvanic cell controls the electron flow to create direct current, where the electrons move in a single direction from one side of the battery to another. However, the secret of the “stored energy” inside a battery is that the electrons cannot flow until it’s hooked up to a complete circuit. Otherwise any battery would drain itself before it could be used.
To understand the individual parts of a cell, let’s have a look at the simplest battery I know; a lemon. Stick a galvanized (zinc coated) nail in one end, and a copper penny in the other side. Combined with the citric acid playing the role of an electrolyte, you’ve got yourself a functioning battery capable of providing about 1 volt of electricity.
At the nail end, the zinc is oxidized (or more commonly; “rusted”) by the acid which creates a bunch of negatively charged electrons. Those electrons really want to zip over to the penny to balance things out, but they cannot flow through the lemon. Only when the nail is connected to the penny by a wire will the electrons be able to move across. Along the way they will provide electricity to any little lightbulb in its path.
We all know batteries have a limited lifespan. That is a limitation of the chemical changes going on. Eventually the nail cannot be oxidized anymore, and the electrons are happy in their balanced state… so no more flow.
A rechargeable battery can reverse the chemical process when power is supplied to the cell, actually de-oxidizing the metal, and setting things up to happen all over again.
- Source: Galvanic cell – Wikipedia