Naked Science Forum
Non Life Sciences => Chemistry => Topic started by: chris on 20/03/2015 08:05:46
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What is in a battery? How does it make electricity?
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What is in a battery? How does it make electricity?
Do you want a top level answer or are you looking for detail.?
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What is in a battery? How does it make electricity?
Do you want a top level answer or are you looking for detail.?
I'll leave the detail for someone else, my typing fingers are tired at present. But regarding the motion of the ionized elements within the battery, this detail comes to mind and it has a bearing on another thread where positive and negative aspects of reality are debated.
Because the current within the battery is circular in nature, and the path the electron takes is opposite to that which is on the outside, many people wonder why the electron is given the negative sign. It's because the current flows from the positive side to the negative side inside the battery. Outside the battery, the current flows from the negative side to the positive. The electron was given the negative sign of charge because we tend to view things from the outside position. We have a member here that is hung-up over the electron having the negative sign. In truth, it really makes no difference, the sign is just a common convention that brings standardization.
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We have a member here that is hung-up over the electron having the negative sign. In truth, it really makes no difference, the sign is just a common convention that brings standardization.
A little learning, and less thinking means people can get hung up on trivia.
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Internal electrical activity, through chemical energy into electricity.
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What is in a battery? How does it make electricity?
I'll leave the detail for someone else,
As no electrochemists have stepped fwd I'll have a go at a very simple description.
Two dissimilar materials are placed in a chemical called an electrolyte - usually a liquid or gel. A chemical reaction takes place in which one of the materials loses electrons and the other gains them. If the two materials are then connected by wires outside the battery, electrons will flow from one material to the other. It is the flow of electrons that makes what we call electricity. The two materials are effectively the terminals of the battery, + and -.
The reality of construction makes the above description very simplistic.
Ethos has described, in a previous post, the way we view positive and negative in a battery.
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why the electron is given the negative sign
Benjamin Franklin was one of the early experimenters with electricity. This site (http://web.engr.oregonstate.edu/~traylor/ece112/lectures/elect_flow_vs_conv_I.pdf) claims that he came up with the convention about which battery terminal is positive or negative.
Franklin (who died in 1788) had no way of knowing about electrons or that they clustered at the negative terminal, so I think the +/- labels on a battery could not have originally represented a flow of electrons inside a battery. The existence of the electron (and the discovery that it came from the negative terminal) was only found in the 1870s (http://en.wikipedia.org/wiki/Electron#Discovery), with the use of high-voltage vacuum tubes.
Depending on the material through which the electricity is flowing (http://en.wikipedia.org/wiki/Electric_current#Conduction_mechanisms_in_various_media), it may be a motion of negative electrons, or positive ions. In a battery electrolyte, there is a flow of both positive ions and negative electrons.
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The official definition of positive and negative is in fact cat fur and ebonite, and has been since the dawn of electrostatics. If you rub an ebonite rod with cat fur, the rod becomes negatively charged and the cat fur, positive. Franklin et al demonstrated the equivalence of static and current electricity, hence the battery terminal designations. The "generator" and "motor" rules, Fleming's Rule, and most of electrical engineering convention, has current flowing from positive to negative, as you can see when you put an ammeter in a circuit.
The charge carrier in solid aluminum or a p-type semiconductor, is a positive hole, not an electron or an ion.
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The official definition of positive and negative is in fact cat fur and ebonite, and has been since the dawn of electrostatics. If you rub an ebonite rod with cat fur, the rod becomes negatively charged and the cat fur, positive. Franklin et al .....
Do you know why Franklin decided the rod should be the -ve?
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The charge carrier in solid aluminum or a p-type semiconductor, is a positive hole, not an electron or an ion.
It is still electrons moving. There is no hole particle (or wave). It's just easier and equivalent to describe the dynamics by counting where the electrons aren't (holes) than where they are (electrons).
For those who haven't thought about holes much before: Imagine you have a 1000 buckets in a line, 999 are filed with water and one is empty. If you always pour water into the empty bucket from a neighboring bucket, the position of the empty bucket will move down the line. It's still water moving, but it's much easier to count and locate the one empty bucket than count and identify all the full ones. Same case with 994 full buckets and 6 empty ones (in fact now it's much easier to follow the different ways 6 empty buckets can be arranged than the ways that 994 full buckets can be arranged, even though they both ultimately give exactly the same answer.) You can do the exact same thing if the situation is reversed, with a vast excess of empty buckets and one or a few full one(s) that move(s) around--it's always easier to count the smaller number, but it's still water that's moving from one bucket to another.
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The official definition of positive and negative is in fact cat fur and ebonite, and has been since the dawn of electrostatics. If you rub an ebonite rod with cat fur, the rod becomes negatively charged and the cat fur, positive. Franklin et al .....
Do you know why Franklin decided the rod should be the -ve?
Because if he hadn't, it would have been positive, and thus confused all his successors. Remember that according to Tony Blair, history is something that happens in the future and judges the past - and who am I to doubt him?
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You can do the exact same thing if the situation is reversed, with a vast excess of empty buckets and one or a few full one(s) that move(s) around--it's always easier to count the smaller number, but it's still water that's moving from one bucket to another.
Except that in the case of holes, you can use the Hall effect to demonstrate that the moving charge is actually positive. The bucket brigade model predicts the wrong polarity for the Hall voltage for aluminum.
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The official definition of positive and negative is in fact cat fur and ebonite, and has been since the dawn of electrostatics. If you rub an ebonite rod with cat fur, the rod becomes negatively charged and the cat fur, positive. Franklin et al .....
Do you know why Franklin decided the rod should be the -ve?
Because if he hadn't, it would have been positive, and thus confused all his successors. Remember that according to Tony Blair, history is something that happens in the future and judges the past - and who am I to doubt him?
Ah, and there was me thinking there might have been some logic to it - would have made a good politician! [:)]
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What is in a battery? How does it make electricity?
A good place to start is: http://en.wikipedia.org/wiki/Battery_%28electricity%29
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You can do the exact same thing if the situation is reversed, with a vast excess of empty buckets and one or a few full one(s) that move(s) around--it's always easier to count the smaller number, but it's still water that's moving from one bucket to another.
Except that in the case of holes, you can use the Hall effect to demonstrate that the moving charge is actually positive. The bucket brigade model predicts the wrong polarity for the Hall voltage for aluminum.
I agree the "bucket brigade" is an overly simplistic model. It's been a while since I have thought about the Hall effect, I'll have to look into it again. My recollection, though, was that it is an issue of whether the electron group velocity is in the same direction as the phase velocity or the other direction. So it's still electrons "moving," but in more complex ways than just single discrete electrons hopping in one direction or the other.
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as a former director of a major "battery Company" there are many answers to your question.
firstly a battery is either a single electrochemical cell or a combinationof cells to make "a Battery"
I should not hide my connection with my French Company which goes back to Leclanche (poitier) and Volta etc.
so Un Element or cell is the first step. A battery is a confusion?? is a "AA" cell what you call a bettery?
Next step is to take the management view about a battery which is " its a container with two terminals in which there are chemicals/elements"
Next step it enter two types of people. The first is an artisan who creates batteries as an art using evolved electrochemistry from years past.
Some of the most successful battery companies are based on black art.
Today, the battery industry is in effect a packaging industry, putting various chemicals and elements into prismatic/cylindrical/button/flat pack containers--- not forgetting my own spherical miniture battery patent based on the same principles as the jewellery industry makes pin head size hollow beads (this Patent now out of time is used incertain special applications.
So now enter Faraday and Leclanche, Volta etc
We enter real electrochemistry and now a new form of near solid state batteries where we play with the magic terms energy density, specific power, power density.
Additionally we enter the zone where batteries chemistry works, just at normal temperatures but at temperatures up to 800 degrees "C"
Thermal batteries where life and chemistry come together.
Hidden in all these words is either its a black box with two terminals or an electrochemical devices, sometimes based on advanced electrodes and electrolytes (some inflamable)
Batteries and most of our modern science is based on material science. New forms such as Nanotechnology will lead to better one off primary and better rechargeable units.
All of this is about electrons moving (where probability clouds or Thompson electrons) between electrodes.
I will not enter into the zone of fuel cells and other forms.
your question leads in many directions.... start by reading Michael Faraday's biography and if you want fun, just take a look at the patents of Thomas Edison where one battery type ( Nickel-Iron) is still a great long long life battery applicable to solar storage.
I have said enough but either its a container with two electrodes or enter into graduate level chemistry, starting by pinning the periodic table on the wall and follow how batteries have evolved over the last 150 years.
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I forget to say that if you want a good basic answer to your question
Just go to YOUTUBE and put in "what is a battery" the various versions give you a good basic intro.