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Static Electricity
Zapping your best friend

It's all about electrons
The Bohr(ing) Model of the atom

Yes, I am aware you probably already know all about atoms, but this is where electricity starts, so we have to go over it any. Everything, and I do mean everything, is made out of little, sphere like structures. These things are damn tiny. Like a million times smaller than the smallest things you can see. They are made up of three parts, the proton, the neutron, and the electron. As far as electricity is concerned, we only need to know about protons and electrons, so you can forget all about neutrons, nobody likes them anyway.

In the Bohr model of the atom, the electrons orbit the nucleus. The electron has a negative charge and the proton has a positive charge. The size of the negative charge is exactly equal to the size of the positive charge. How do we know this? People with no lives measure it. That's how.

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Electricity is just like dating!
OK, so it's not as fun, but stay with me on this

Likes repel and unlikes attract. It's just like the average heterosexual's day. (I apologize to the rare female physics enthusiast for the following examples, please just reverse the genders, and call me. I'm single ladies! Big surprise huh?)

OK guys, here is how to remember that little rule. Lets say you are looking for sex. Think about having sex with another guy (a member of the same sex). Aren't you repulsed? (assuming you're not gay) Well it's the same thing with electrons, they do not want anything to do with each other. They feel a repulsive force when they get close to each other.

Now think about having sex with a female (a member of the opposite sex). Attracted to the idea aren't you. Wait! Don't leave and download porn! Stay here and read the rest of this! Pervert. Anyway, once again, it is the same thing with electrons. They always want to be near their opposite, the proton. They feel an attractive force when near a proton.

All of electricity is just based on the movement of charges. The same kind of charges (likes) repel each other and different kinds of charges (unlikes) attract each other.

Charging things
If I hear one credit card joke...

Everybody has been zapped by a little brother at least once in their life. The little kid, apparently having nothing better to do, shuffles around on the shag carpeting for hours in his socks until he is brimming with charge. Then when you least suspect it, he flings himself at you. A massive lightning bolt passes between the two of you. You then proceed to beat your brother into a bloody pulp for disturbing you during a particularly good 'Voyager' episode. How did your brother get that charge? Read on.

Imagine you are at a party. Once again you are out for sex. As you survey the scene you notice a particularly hot girl. Unfortunately there are already several males orbiting around her. Although you are still attracted to her, the surrounding males decrease her attractiveness with their repulsiveness. You may attempt to swoon her, but the fact that there are other males around diminishes your chances of scoring. The point is, you may stick around for a little while, hoping for the best, but if a hot girl with fewer or no male attendants passes by, you will desert the first girl to try your luck with the second. The same kind of thing is happening with charges.

A note to any advanced physics people reading the following paragraph. I know this is not an exactly correct metaphor, but I feel it is good enough for first year physics students.

The socks on your brother's feet, and the carpet are (obviously) not made out of the same material. Different materials (usually) means different kinds of atoms. That means different numbers of electrons and protons. Now follow me on this. Lets say that the average atom in the carpet has more electrons (males) orbiting the nucleus of protons (females) than does the average atom in the socks. When your brother rubs his socks against the carpet, he provides energy for the electrons (males) in the carpet to 'jump ship' and go onto the socks where there are less electrons (males) around each proton (female). Obviously, this is where the males would like to be, a place where the chance of scoring is better!

But wait a minute! Now the carpet has less electrons than it should, and the socks have more electrons than they should! What happens? A charge is the result of this imbalance. The socks, which have more electrons than God ever intended sock to have, now have a negative charge. The carpet, which now has more protons than electrons, gains a positive charge. The important thing to remember is that, the size of the two charges is exactly the same. No electrons were created or destroyed in the charging process. I think a picture would be helpful right about now.

In the above gif we see what the sock and carpet look like before your brother rubs his feet on the floor. In reality there should be trillions upon trillion of electrons and protons, but I didn't feel like drawing trillions, I drew fourteen. Both the sock and the carpet are electrically neutral. If you add up the charges you get 0. This is how most thing are normally found. Now lets have your little brother rub his feet on the floor.

Things have changed, the sock gained an electron and the carpet lost one. The sock now becomes electrically charged and so does the carpet. The important thing to notice is that the total charge stays the same. This is called, unimaginatively enough, "The law of conservation of charge".

More specifically, the law of conservation of charge says that you can't just make electrons or protons disappear. They have to come from somewhere. Conversely, you can't just make electrons or proton appear from nothing. They to have to come from somewhere.

One more thing to note: ONLY THE ELECTRONS MOVE! The protons always stay right where they are. They NEVER move. It's always the guys (electrons) who are running around all over the place, buying flowers and Teddy bears for their targets of affection, the protons.

The Formula
You knew it was coming, don't look so surprised

The force of attraction or repulsion between two charges is equal to the electrostatic constant 9.0 x 10⁹ times the magnitude of the first charge times the magnitude of the second charge, divided between the distance between their centers squared.

Look a bit familiar? It should, the French guy who came up with this, Coulomb, kinda ripped off Newton's gravity formula. But since it works, we can't complain.

Now we have to define the magnitude of the charge. Since it would be incredibly inconvenient to write the number of extra or missing electrons, we use a coulomb. Yes its the same guy who thought of the rule. A coulomb is defined as 6.25 x 10¹⁸ electrons. That is a damn lot of electrons.

Different ways of charging stuff

Conduction

This is the simplest way to charge something. Simply take something else that is charged already, like your little brother, and have it touch an uncharged object, yourself. Sparks fly and now both you are your brother are charged.

Can you see the downside to this method? The downside is that the two objects share the charge. I.E. if your brother had a coulomb of charge, and you were neutral, after the contact, you would each have ½ coulomb charges. This is because of conservation of charge. Since you can't just create new charges, and since charges like to spread out, the two of you would share the charge.

Just to be picky though, the above example only works if the two of you are about the same size. If you are a great deal larger than your brother, you will get a proportionally larger share of the charge, however the ratio of charge to surface area of you and your brother will be the same. Also if your brother actually had 1 columb of charge the two of you would be dead. 1 columb is a huge amount of charge. We normally don't see that much charge just sitting around on a Saturday with nothing to do.

Induction

If you bring a charged object, your brother, near an uncharged object, the cat, your brother will induce a charge on the cat. How does this work? Let me explain.

Remember that likes attract and unlikes repel? OK good. Lets say that your brother has a negative charge. When he comes near the cat, or any other object for that matter. He repels the electrons in that object. That is to say, some of the electrons on the side of the cat near to your brother, travel to the far side of the cat. So now we have a cat with a positive and a negative side. Overall the cat is neutral though, it still has the same number of electrons and protons as it did before, they are just relocated.

Once your remove the charged object, your brother, the electrons in the cat return to their normal position, and she looses her charge.

Charging by Induction and Grounding

Just so we are all on the same page, grounding is how you remove a charge from something. Just touch it to the ground! Or a conductor that is touching the ground. The earth is basically a huge neutralizing ball. It will add or take away elections as needed to return an object to neutral. The Earth can do this because it is so huge, it as so many electrons, that gaining or loosing a few doesn't matter. That's grounding.

Charging by induction and grounding really isn't too complicated, but it does seem to give people problems anyway. To start out you induce a charge in some object. So all the electrons run to one side. If you then attach a ground, the electrons have a place to run to, instead of just being trapped on the original object. So they all bail ship and leave the object with fewer electrons than before. Then you remove the ground, then take away the object you used to induce the charge, and you are left with a permanently charged object.

By the way, it also works if you use a positive object to induce the charge, the only difference is that elections go onto the object you want to charge through the ground.

If any of the above was unclear, or if you have any comments or suggestions, please E-mail me!

ColinGPalmer@hotmail.com

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