[Potironette]

So..electrical energy means energy from electrons?

I've not really learned about energy other than mechanical though--so the first thing I wonder at is that electrons are moving. Though when I think back I'm guessing electrical energy does not involve contact, whereas mechanical does, so that's why they're different? Though I've not yet learned about field forces other than the fact that gravity is an example of a field force.

Actually, what does moving mean? Don't electrons move in clouds or something all the time? Does moving mean it needs to transfer to another place..?

If I stick a piece of metal into a potato will it heat up? Or does it still need another end connected to the potato?

But the energy needs to be converted into chemical(?) energy? I sort of learned about rechargeable batteries last year but forgot a lot of it. Something about electrons moving places is all I remember. It's sort of interesting how energy needs(?)/can be converted to be stored and reused. I don't understand how solar panels and windmills and coal can possibly be used as energy when I think about it.

[Coda]

Energy OF electrons, not energy FROM electrons. But otherwise, close enough.

You are 100% correct that electrons are moving. Electricity on its own, however, DOES require contact, at least at the macro scale. That's what wires are for -- the electrons in the metal atoms are able to move without a lot of resistance (sort of analogous to friction), so when you pull electrons out of one side of a wire, electrons will ripple through to fill up the void you created. If this were to leave a void on the other side, though, the electrons would just flow back. (Yes, this means that electrons are constantly swirling around in metal, but if you think about it, you already knew that electrons are constantly swirling around -- it just means they're able to swirl around in a little bit bigger of a range than you might have expected.) In order to get an actual electrical current, then, you need to have a source of electrons on the other end to refill what you took out.

But electricity isn't the only effect in play here.

When electrons move, they create a magnetic field. And when magnetic fields move, they cause electrons to move. This is how windmills generate electricity, actually: the rotation moves a bunch of magnets along a bunch of coils of wire, so the magnets sort of drag electrons along, pushing some electrons down the wire and pulling some up from the other end. If you put a load between the far ends of the wire, like a light bulb, then you can make those moving electrons do work.

There are also electric fields. Protons have a charge of +1. Electrons have a charge of -1. A normal atom has equal numbers of protons and neutrons, so the net charge of that atom is 0, and so the net electric field of that atom is zero. But if an atom has more or fewer electrons, then it gets a net charge. We call such a charged particle an "ion" and it has a negative or positive charge, and it has an electric field with a strength and polarity based on that charge. (Ions can also be formed by multiple atoms bonded together; bonded atoms "share" electrons in a sense, so if any of those atoms are missing electrons or have excess electrons, the whole bonded group acts as an ion.) Oppositely-charged ions attract each other; ions with the same charge repel each other.

In clouds, you have ice crystals banging around a lot, and sometimes when they do, an electron will move over from one to another. This gives one crystal a positive charge, and one crystal a negative charge, and usually (for reasons that aren't well-understood) the bigger crystal is the one that ends up with a negative charge and the smaller one ends up with a positive charge. Those crystals do attract each other, but the attraction is fairly weak, and they have so much kinetic energy from being blown around in the air that they get separated. The heavier negative crystals filter towards the bottom of the cloud and the lighter positive ones filter towards the top. This creates a charge differential -- that is, an electrical potential, a place where an excess of electrons desperately wants to move over to a place with a shortage of electrons. Cloud lightning happens when the potential gets so great that it overcomes the resistance of the air (just because it's very high doesn't mean it's infinite) and the electrons take the shortest path from negative to positive.

Lightning strikes happen because that massive negative buildup in the cloud attracts positive charge in the earth to amass at the surface below. It takes a LOT of potential to overcome THAT much air, but as soon as even two little points get enough charge to get past the resistance of the shortest route between them, BOOM.

As for a potato battery: No, one piece of metal isn't enough. It requires two pieces of different kinds of metal (usually copper and zinc). There's phosphoric acid in the potato, and the speed that the acid can cause chemical reactions is entirely dependent on how fast the it can ionize the metal atoms, which is why you need two DIFFERENT kinds of metals -- one kind of metal will part with its electrons more readily than the other, and so that chemical reaction can happen more easily. This creates a charge differential, and if you connect a wire to the two kinds of metals, electrons can flow through it from the slower side to the faster side, facilitating that reaction.

As for why it doesn't pull the electrons back, the zinc ions react with the acid, creating zinc phosphate and positively-charged hydrogen atoms, which are drawn towards the now-negatively-charged copper. They pick up those extra electrons to become hydrogen atoms (and then react with other hydrogen atoms to create molecular hydrogen gas, which you can see bubbling at the copper metal if you set it up in a beaker instead of inside a potato). And so Newton's laws are conserved and the net charge of the system as a whole remains balanced, but you've derived work from the energy stored in chemical bonds in the potato.

Eventually, the potato will run out of phosphoric acid around the zinc metal, because it'll have all turned into zinc phosphate... and so the battery will be dead -- no more chemical reaction means no more ions means no more electron flow.

Some chemical reactions, such as the ones used in lithium batteries, create compounds that can be broken back apart easily by shoving a little bit of energy at them. And then if there's no path for electrons to flow (that is, you disconnect the load), then that reaction will sit there in tension, waiting for a source of electrons to let it finish.

Solar panels basically work by having a special kind of metal surface, so when a photon hits it, it knocks an electron off, so an electron gets pulled in to fill the void, and that creates a current flow.

Coal is a completely different thing. You can't actually create ELECTRICAL energy from coal. Instead, you burn coal, adding a little bit of energy to break apart a big molecule, and breaking the molecule apart releases more energy than it took to break it, so that creates heat. The heat is used to boil water, and the steam is used to spin a turbine, and the turbine is used just like the windmill above. Why yes, burning stuff IS an inefficient way of using energy.

Nuclear energy works the same way, except instead of breaking apart big molecules by setting them on fire, you have big atoms that flake off pieces of themselves on their own (radioactivity), and when they do that the particles they release have a chance of hitting other big atoms and making them split (atomic fission). In both cases, that produces energy... which gets used to boil water to spin a turbine to spin a magnet through a coil of wire. Nuclear power plants are actually not especially efficient either, but nuclear reactions generate SO MUCH raw energy that it doesn't much MATTER.

EDIT: O.o 55 aurum megapost

EDIT 2: I was wrong about the specific details of the chemistry of a potato battery. I've corrected that.

[Potironette]

Lol xD. That's a long post.
Thanks for the detailed answer though!

I guess I should probably learn more about fields and currents before understanding how magnets generate electricity :/. Whenever I look for it, there's a lot about how generators are made up of different parts, and depending on the parts currents flow either back and forth or forwards, but I don't really understand exactly how the currents are flowing in the first place--as in why the magnets are causing that sort of current flow, and then there's how the weird circle part (I forgot the name) can make the electrons not flow back and forth but rather just flow forward.

Earth has a positive charge :o? Or it just has a more positive charge than the cloud..?

Soo... if a cloud is really high up, the shortest path might be between clouds or within the same cloud, and if it's lower on the ground electrons move from the bottom of the cloud to the ground?

If I had copper and zinc would it be extremely bad idea to connect them together and stick the ends into a power outlet xD?

Ohh, woops, I'd forgotten that chemical reactions were important in batteries.
Actually, because I forgot about it, a lot of it flew over my head. Though I do recall something about how one end needs to lose electrons and starts falling apart and the other end gains electrons and gets a coating.

What does "knocks an electron off" mean? It's not that the electron literally flies out of the metal surface is it..?

[Coda]

Earth has a net neutral electric charge. But you can induce a charge in an object by bringing another charged object near it; it'll push matching charges away and pull opposing charges near -- electrons are very, very mobile little things and it really doesn't take a whole lot to move them around. So there's a positively charged region that's formed below the cloud.

You're completely correct about the motion of lightning. Note, of course, that it's (ionized) air itself that ends up conducting the electricity, so the path of least resistance might not be the shortest STRAIGHT-LINE path.

If you had copper and zinc, it would be a bad idea to stick it into an outlet, but not because it would form a battery... it would be a bad idea because you would be creating a path of least resistance between the two sides of the power outlet and that much energy flowing through a couple tiny bits of metal will start a fire. The fact that they're different metals is irrelevant there.

You're remembering the chemistry relatively well there. All consistent!

And yes, the electron literally does get displaced from where it was. It sticks mostly close to the surface, skidding across to other atoms, pulled towards positively-charged things. It doesn't go flying off the surface -- that would be a beta ray, and that takes a lot more energy.

[Potironette]

Oh woops. The reason for copper and zinc was for the chemical reaction(?) so all that's needed is anything with least resistance to stick into the power outlet? Oh, but does anything happen if only one side of a power outlet gets a metal strip stuck into it?

[Coda]

Depends on what the other end is connected to. If the other end is connected to YOU, and you're touching the ground with your bare skin, then the electricity will happily go from you to the ground, because the Earth itself can soak a ton of current.

Not wise.

[Potironette]

Too bad there isn't a good way to see it without killing myself x'D.

Is electrons rushing through a human body ok? What's the alternative? I'm reminded of how people may survive or may not survive lightning strikes, but I don't remember what it was that let people live, or that killed people.

[Coda]

Electrons rush through your body all the time. It's how your nervous system works. And small amounts of extra current aren't damaging -- there's an experiment you can do where you set up a little buzzer circuit that makes a noise when electricity goes through it, and the pitch of the noise varies according to how much resistance there is between a couple of electrodes, and you can hold the electrodes in your fingers and control the sound just by how tightly you press your skin against the metal. It's harmless fun.

The problem is that resistance is a lot like friction. What happens to the energy that's lost due to friction in a kinetic system? It turns into heat. The same is true of electricity. We use this phenomenon intentionally in electric heaters and incandescent light bulbs (as we discussed in the past, get it hot enough and the light becomes visible). But your body has electrical resistance too, and if you put too much current through it, that heat will end up cooking you.

If you don't want to do this to your OWN body, of course, it's completely plausible to do this with an experimental setup. If you connect a power outlet to a couple of wires, and put those wires in opposite ends of a pickle, it'll light up like a fluorescent bulb! Don't actually TRY this at home unless you know what you're doing because you don't want to start fires or route the current through yourself -- after all, YOU don't want to be a light bulb.

The other risk is that your body DOES use electricity to communicate signals through your body. If you push too much current through those pathways, your nerves will get overloaded and all sorts of nasty stuff can happen -- for example, you could destabilize the electrical oscillator responsible for keeping your heart pumping, which will put you in cardiac arrest. (If you've ever heard of someone having to have a pacemaker implanted, it's an artificial replacement for that.)

Lightning strikes have a fairly good prognosis, medically -- roughly 80% of strike victims survive, although most have long-term injuries. It's easier for the electricity to flow over your skin to the ground than to pass through your body, and lightning is a single burst of power instead of sustained high-voltage exposure like you might get from touching electrical wires. Strike victims usually have to deal with problems like burns (from the electricity damaging the cells directly, not from the heat itself, which doesn't last long enough to cause burns that way), flash blindness, deafness, heart attacks, and seizures, but while those can be dangerous conditions, they're survivable with proper care.

[Potironette]

It's a good thing youtube exists for seeing pickles light up xD. I wonder why it is that it seems like pickles light up at one end, then for the rest of the time only light up at the other end.
I'm guessing it's pickles because electricity runs through salt easier?

Thanks for all the info on the human body and lightning!
So..lightning strikes more often flow over the skin and maybe cause some burns in the process. Or lightning strikes might go through the body while causing burns and messing up how the nervous system(?) is communicating(?) using electrons(?) through synapses(?)(I don't really remember anything about synapses but it reminds me of electric things '~').

[Coda]

Yes, salt water is the reason. I think the reason it lights up at one side is because that's the side the electricity is coming in from, and the other side is where the now-much-less-energetic electrons go out. Not 100% sure.

Through nerves, not through synapses. Synapses are chemistry-based bridges between neurons, using ions to create a potential difference (that is, a voltage).

[Potironette]

Ohh so that's what synapses were, woops.

But why would it matter that that's the side that electricity goes out because it's flowing either way?

[Coda]

Imagine pouring water through a funnel into a pipe. On one end, you've got lots of water splashing around and if you try to pour too much in it overflows. On the other end, the water comes out in a nice even stream. The pickle is an overflowing funnel -- the light happens because there's more energy coming in than can flow smoothly through the medium.

[Potironette]

Ohh okay, that makes sense! I'm wondering why electrons give off light when they're not flowing smoothly, but I guess I might as well question why things make sounds when they hit other things xD

[Coda]

Electrical resistance is very much like friction, as I mentioned before. It converts kinetic energy into heat.

As for objects knocking into each other making noise: it's a shockwave! The speed of sound in an object is actually measuring how fast force can propagate through that material.

You already know Newton's third law. Object hits other object; other object exerts force back on first object. Well, imagine that down at the atomic level. The atoms at the point of collision get knocked into the atoms behind them, which get knocked into the atoms behind them, etc... and how quickly this happens is what defines the speed of sound in that material.

Well, on the other side of the object, the atoms get knocked back, but there aren't any other atoms of the material there to bump into -- instead, they bump into the atoms of the air. And those get knocked back through space until they hit something, and so on and so forth.

Eventually, if one of those hits your eardrum, it stimulates some nerves, and you perceive it as sound.

And now you know what a sound wave is -- it's kinetic energy getting rapidly transferred from atom to atom through a series of collisions. (Well. Technically not collisions. At the subatomic scale, everything's a field force, so really it's the atoms repelling each other when they get too close together. But at the macro scale, that's a collision.)

[Potironette]

Oh wow! That's really cool what a sound wave is! But since it's from atoms hitting all the way to the other side, does that mean when someone knocks on a door, the person inside the room hears it louder than the person outside (assuming that the person inside just happens to be right at the door)?

And by sound "in" an object you mean it's because the atoms are in the object?


From what I remember, friction happens because of temporary dipoles..and those cause a sticky effect between objects. Buut why does electrical resistance occur? From too many electrons bumping into each other o_o?

[Coda]

Well, maybe, maybe not. Acoustics is a very rich field, so I'm sure you can imagine that a lot of factors play into that perception.

So first off, being three-dimensional, that energy spreads out in a spherical wavefront. The farther from the source, the larger the sphere, so that energy is spread out over a greater area. This is, in fact, the primary reason why sounds get quieter the farther away you are. And since a sphere's surface is two-dimensional, you can observe that the loudness is inversely proportional to the square of the distance, that is, at twice the distance it's 4x quieter -- this is called the inverse square law and it comes up in a LOT of places. So if you're closer to the source of the sound than the other person, you might hear it louder.

Second, there's a loss of efficiency when the energy has to move between regions of different density, such as from a solid door into the gaseous air. This is because some of the energy gets reflected instead of transmitted -- just like light shining on a piece of glass; some bounces off instead of going through. This is why sound gets louder if you cup your hand around your ear (some of the sound bounces off of your skin instead of passing through, and it gets redirected into your ear) and why it gets muffled if there's a wall in the way. On the other hand, the sound might echo inside the room, allowing more of the energy to come to the other person's ear, but the sound on the outside will just disperse out into the air.

That effect also applies to the act of knocking itself. Some sound goes into the door; some sound reflects. Depending on how the door is constructed, it might transmit the sound well, or it might muffle it, and it might reflect the sound well (so you hear it better) or it might not (so it sounds a lot duller to you than on the inside).

There are other things, but I think that's enough of an answer for now. :P