My understanding of batteries is that chemical reactions inside of them produce electrons than then flow through the electric circuit and to the positive post. What happens to those electrons when they reach the positive post?
In: 3
They slip into a positively charged atom (called an ion) changing it into a neutral atom of whatever the positive post is made of.
They get scooped up into the electrolyte and pumped back to the negative end. This process continues until the voltage gets high enough that the electrolyte can no longer shuffle the electrons over. Then, the process stops – this only happens when current stops flowing.
Imagine a roller coaster ride. The negative terminal of the battery is the beginning part of the ride where the roller coaster gets brought all the way up to the top. It is then release and you go wheeeeee through the whole circuit.
So what happens when you finally reach the starting point again? Well, you can brought up to the top again. That’s what the battery does. The positive terminal is the top of the ride (think positive gravitational potential energy) and the negative terminal is the bottom of the ride, or the starting point where people board the roller coaster. The entire roller coaster ride is the electrical circuit. The energy that you get when you are brought to the top is converted into other (usually useful) forms of energy.
A chemical battery is made out of two different metal ions – one is called the anode, and one is called the cathode. The anode has extra electrons to lose, the cathode wants electrons. If you connect the two via a wire, electrons will flow from the anode to the cathode. Those electrons will have some energy that you can use to power your circuit.
When the electrons reach the cathode, they bond with the ions in the cathode, making them no longer ions. You’ll eventually reach a point where the anode has no more electrons to give – which makes the battery stop working. If it’s a rechargeable battery you can apply an external current to reverse the flow of the electrons… if it’s not, you just have to recycle the battery and get a new one.
you know how salt crystals are sodium and chloride, which are bound together into a structure? They stick together because the chlorine “wants” electrons, and the sodium has “too many” electrons. So the sodium gives it’s extra electron to the chlorine, and then they stick to each other because they are now magnetically charged. Any molecule that acts this way is called a *salt*, and will happen between atoms on opposite extreme edges of the periodic table (Lithium, potassium, sodium, florine, chlorine, iodine…)
A battery is created by taking two substances that want to form a salt, and putting a wire between them. Now to trade that electron it has to be pushed through the wire to get to the other atom and be absorbed. So you put potassium on one side and chlorine on the other, and after the charge is depleted you have a pile of potassium and chlorine ions that are now happy with the number of electrons they have, and no longer want to trade
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On potential energy
The *electrical potential* of two atoms is measure of how badly those two atoms “want” to trade their electrons, the more they want to trade, the more potential energy there is that will be released once that exchange takes place, which can be used to power things. Thus the higher that potential the more *voltage* will be pushed through the wire, thus more energy will be available, but the faster the energy will be used up (like tilting a bucket of water further over, it pours out with more force, but will empty faster). So you can upend the electron bucket by hooking up cesium and iodine and end up with something that will explode the second you close the circuit, or you can take two atoms that barely want to talk to each other (say, lead and hydrogen, which make up your car’s lead-acid battery) and get a slower trickle that will last a very long time.
As we get better at controlling ions, we are getting more comfortable using more unstable elemental combinations, this is why modern batteries have issues with catching on fire on occasion – they are putting more potential in the same space and counting on a lid to keep the water from coming out of the pot too fast, but sometimes there’s an engineering mistake and the lid doesn’t stay on right, and suddenly your phone is now a bomb.
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On wire
some atoms are special, and have multiple *happy* places. Sodium wants 10 electrons and has 11; chlorine has 17 electrons and wants 18, but copper is happy with 30 OR 31(similarly iron is happy with 28 OR 29); thus copper will happily carry that electron from the sodium to the chlorine, because it has 30, but is “content” to take a 31st electron from sodium and hold onto it (since sodium doesn’t want it), and then the copper at the other end of the wire is happy to give up it’s 31st electron and go back down to 30, since the chlorine is asking nicely for it. This feature is what makes some things conductive and other things not.
There are other special atoms that specifically DON’T want to mess with their electron count, for example large covalently bonded carbon chains (such as rubber) have the “perfect” number of electrons, and will reject any new electrons trying to join the party. These substances act as insulators.
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fun fact
your muscles work via a chlorine/potassium battery interacting with a chlorine/sodium battery. that’s why you get cramps when you don’t have enough potassium, and “electrolytes” are so important for the body – electrolytes is just a fancy nutrition term for these salts that can create electrical potentials.
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