Electrons and Batteries

[CoryDuchesne]

Here's an explanation for how a simple battery works:

 

Probably the simplest battery you can create is called a zinc/carbon battery. By understanding the chemical reaction going on inside this battery, you can understand how batteries work in general.

 

Imagine that you have a jar of sulfuric acid (H2SO4). Stick a zinc rod in it, and the acid will immediately start to eat away at the zinc. You will see hydrogen gas bubbles forming on the zinc, and the rod and acid will start to heat up. Here's what is happening:

 

* The acid molecules break up into three ions: two H+ (hydrogen) ions and one SO4-- (sulfate) ion.

* The zinc atoms on the surface of the zinc rod lose two electrons (2e-) to become Zn++ ions.

* The Zn++ ions combine with the SO4-- ion to create ZnSO4 (zinc sulfate), which dissolves in the acid.

* The electrons from the zinc atoms combine with the hydrogen ions in the acid to create H2 molecules (hydrogen gas). We see the hydrogen gas as bubbles forming on the zinc rod.

 

If you now stick a carbon rod in the acid, the acid does nothing to it. But if you connect a wire between the zinc rod and the carbon rod, two things change:

 

* The electrons flow through the wire and combine with hydrogen on the carbon rod, so hydrogen gas begins bubbling off the carbon rod.

* There is less heat. You can power a light bulb or similar load using the electrons flowing through the wire, and you can measure a voltage and current in the wire. Some of the heat energy is turned into electron motion.

 

The electrons go to the trouble to move to the carbon rod because they find it easier to combine with hydrogen there. There is a characteristic voltage in the cell of 0.76 volts. Eventually, the zinc rod dissolves completely or the hydrogen ions in the acid get used up and the battery "dies."

 

I just don't understand why the electrons find it easier to combine with the hydrogen on the carbon rod. The electrons are orbiting the hydrogen atoms on the zinc rod. Why would they want to move?

[hermanntrude]

Here's an explanation for how a simple battery works:

 

 

 

I just don't understand why the electrons find it easier to combine with the hydrogen on the carbon rod. The electrons are orbiting the hydrogen atoms on the zinc rod. Why would they want to move?

 

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If there is a moderator around, perhaps they could insert this link:

 

http://www.howstuffworks.com/battery.htm/printable