Do you have anything that uses batteries? A flashlight? A radio? What is a battery anyway?

A battery is a set of electrochemical cells put together. An electrochemical cell is a package of chemicals designed to produce a small amount of electricity. You do not see the individual cells in a battery because they are all sealed into a case with only one positive and one negative terminal showing. In this activity, you will learn how batteries work.

Inside every battery are three main ingredients: an electrolyte and two electrodes.

• All batteries must have some form of an electrolyte. This is a paste or liquid made of chemicals that conduct electricity.
• A battery must also have two electrodes (an anode and a cathode). The cathode is the negatively charged electrode. The anode is the positively charged electrode. These are metals that react with the electrolyte. The protruding end of the battery (positive) is positively charged; the flat end of the battery (negative) is negatively charged.

 

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Take a look at the diagram below that shows the electric flow in a battery.
  

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There are two main types of batteries.

Dry cells are batteries in which the chemicals that produce the power are in a paste. In a dry cell, electrons leave from the negative electrode and return to the positive electrode. The AA batteries used in many items are dry cells.

Wet cells use a liquid electrolyte that is usually an acid. Wet-cell batteries have two pieces of metal in the electrolyte. The acid eats away slowly at one electrode to give it a negative charge. The electrons flow from this electrode through a wire to the other electrode, which is positive. This provides an electric charge. A car battery is a wet cell. A car battery usually has six lead-acid wet cells mounted in one case with two terminals: one + and one -.

Most wet-cell batteries and some dry-cell batteries are rechargeable. In rechargeable cells, the chemical reaction can be reversed by using an external electric source. By reversing the reaction in the cell, the electrodes are returned to their original state. Rechargeable dry cells are used in laptop computers and cell phones.