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As I mentioned earlier, batteries are used in various gadgets in our daily lives.

We will look at how they work internally. I will not be going into details of chemical reactions (like chemical formulas along with the emf values) - but this will be a general look at how they work.

A battery usually consists of one or more cells. If there are more than one cells, then they are usually connected in series.

The cells are usually galvanic cells. There are other types of cells like voltaic, electrolytic, fuel or flow cells. But for our understanding of the internal workings, we will consider them to be just cells.

The cells consist of two half cells. Each of these half cells consist of a electrode and an electrolyte. The half cells are connected to each other through a salt bridge or some kind of porous boundary - so that the electrolytes can interact with each other.

For the battery to function, the half cells would be of different types. The reason is that, if they are same, then they will be having the same emf (electromotive force) potential. The voltage of a battery (that actually powers other devices) is nothing but the difference between the emf of the two half cells. The electrode of the half cell having lower emf of the two, is called anode. It is usually denoted by the (-) sign. The other half cell having a higher potential is called cathode and is denoted by the (+) sign.

This emf of the half cell is a property of the combination chemicals of electrode and electrolyte. For example, a common half cell combination is Zinc (electrode) and Zinc Sulphate (electrolyte) has a emf of -0.76 V. Another combination of Copper (electrode) and Copper Sulphate (electrolyte) has emf of +0.34 V. A combination of these half cells would give us a galvanic cell having a voltage output of 1.1 V. A battery can have more than one cells in series to get a higher voltage output. The cells are said to be in series when the anode of one cell is connected to cathode of another.

When these batteries are used in devices, the anode and cathode is connected to the circuit of the device. The circuit completes the loop, and the chemical reactions take place with in the cells - basically exchanging electrons. The process continues as long as the circuit loop is not broken or the chemical energy exists. The battery gets discharged, when there is no more chemical energy to drive the electrons and create electricity.

Depending on the type of battery (primary or secondary) they can or cannot be recharged. But we will leave the different types of batteries for the next post.

Image is © of bennylin