Electric Current: How Does the Battery Generate Voltage?

[Vicol]

Hello again :)

I've got a serious problem. Generally I know why current flows (free electrons and voltage). But some days ago I was considering about regular battery and electrical circut.

Free electrons in wire flow along circut, ok, that's fine and understandable. But how does battery generates voltage? I know that there are some chemical reactions. But it's not the point. The problem for me is that potential is created by charges. Does it mean that electron in wire flows due to electrons condensed at battery? How do we get potential?

One more time - I don't ask you how we get current, but how do we produce potential? If we obtain it by electrons gathered at battery, do they flow too?

Sorry for my english, It's not my national language :)

 

[ZapperZ]

Your question has more to do with chemistry, i.e. the inner workings of an electrolytic cell.

http://www.av8n.com/physics/battery.htm

Maybe that might answer most of it.

Zz.

 

[Dale]

But how does battery generates voltage? I know that there are some chemical reactions. But it's not the point.

As Zz says, the chemical reaction is the thing that generates voltage. I don't know how this question could be answered without discussing the chemical reaction.

 

[gleem]

A little back ground may help. Some metal ions have a strong affinity (attraction) for electrons . So strong in fact that in contact with another metal they may pull electrons from that metal. For example if you have a solution of copper ions say as a sulfate and you place a piece of zinc in the solution you will see copper being deposited on the zinc after a short time. The copper ion is pulling electrons from the zinc (oxidizing it) and converting itself to elemental copper and placing the zinc in solution as zinc ions (sulfate). This affinity to attract electrons via atomic forces results in the establishment of a potential difference between the two metal atoms.

A battery makes use of this property to produce a source of electron current by allowing one metal to dissolve (i.e. give up a steady supply of electrons) into a solution while the other presently in the solution captures the electrons and is remove from the solution and converted into the pure metallic form.

Practical batteries are often more complex in chemistry and construction but still rely on the fact that one chemical component attracts electrons while another gives up electrons. The voltage of a battery can be obtained from the difference of potential obtained from the Electricalchemical Series. see http://www.ucc.ie/academic/chem/dolchem/html/dict/000e1.html

The potential difference is not due to an accumulation of free charges but an attraction of a charge from one type of atom to another which results in a potential difference.

 

[ehild]

This is copied from an old thread:

Immersing a metal into an acidic solution it starts to dissolve. Positive metal ions from the surface of the metal go over to the liquid, leaving their electrons behind, and making the electrode negative. The ions stay close to the electrode, as it attracts them because of its negative charge, and some of them go back and become part of the metal again. A dynamic equilibrium is established at some potential difference between the ion cloud and metal. Some metals are more ready to dissolve than others, so immersed in the same electrolyte, they become more or less negative. Immersing two different metals in the same electrolyte, there is a potential difference between them, and connected by a resistor, current will flow. The current removes electrons from the more negative electrode, decreasing the attracting force they exert on the positive ion cloud, so some ions can migrate towards the other electrons and neutralize with the excess electrons arriving there through the load. At he same time, as the negative electrode becomes less negative, new ions dissolve and go over to the liquid phase, trying to maintain equilibrium potential difference between the electrodes.
http://alexteoh.com/emap-electrochem/SimpleELECTRICcell.html

You can do experiments with two different metal pieces (steel and brass nail or screw, or two coins of different material) immersing them into slightly acidic liquid and measuring the voltage between them with a multimeter. You can also try inserting the electrodes into a lemon, apple or potato - they all will work.

http://www.how-things-work-science-projects.com/lemon-battery.html#lemon_battery