A battery creates an electric current through a chemical reaction that produces a potential difference between its two terminals. The chemical reaction occurs between two different metals in a chemical substance called an electrolyte. One end of the battery is attached to one of the metals, and the other end is attached to the other metal. A chemical reaction between the metals and the electrolyte frees more electrons in one metal than it does in the other, creating a positive charge in one metal and a negative charge in the other. When an electrical conductor, or wire, connects one end of the battery to the other, electrons flow through the wire to balance the electrical charge. This flow of electrons is what creates an electric current that can be used to do work.