# Help me understand static electricity

This is what I understand about electricity: (The following information is paraphrased from the book CODE by Charles Petzold.)

Atoms are made up of protons, electrons and neutrons. Protons and electrons tend to exist in equal numbers in the atoms to which they reside. Sometimes it is possible for an electron to jump from one atom to another. This is electricity.

The words electron and electricity come from the Greek word for amber. This is because the Greeks discovered static electricity when they experimented with rubbing amber and wool together. In these experiments, the electrons would jump from the amber over to the wool.

More modern day experiments can be conducted with shoes and carpet.

Here is where I am confused:

Petzold says:

When the carpet picks up electrons from your shoes, eventually, everything gets evened out when you touch something and feel a spark. That spark of static electricity is the movement of electrons by a rather circuitous route from the carpet through your body back to your shoes.

After this explanation he moves on to a larger concept, but I am left slightly confused.

• Exactly what is this "circuitous route"? Does the thing I touch also have to be touching the carpet?

• Why did the electrons jump from my shoes to the carpet in the first place?

• If the electrons were transferred to the carpet for a reason, what is it that makes them get transferred back to my shoes?

Exactly what is this "circuitous route"? Does the thing I touch also have to be touching the carpet?

Though I'm not a native English speaker I am pretty sure that a circuitous route is a path that combines you shoes and the carpet as were they a part of a circuit.

The thing you touch has to be connected to the carpet (by touching the carpet itself or by touching some other conductor touching the carpet. There must be a conducting path).

Why did the electrons jump from my shoes to the carpet in the first place?

Electrons are bound in atoms at different energy states. Certain amounts of energy could rip off an electron from an atom, and thereby off from your shoe. By brushing your shoe over the carpet, you are adding energy, and in some points that energy and the force done is intensive enough to rip loose an electron that is left on the carpet.

Moving a charge to a neutral location is not a place the charge would naturally go. At the same time the electron might be held tight to the original atom. Force must be done to add enough energy to overcome such energy barrier.

If the electrons were transferred to the carpet for a reason, what is it that makes them get transferred back to my shoes?

Since you moved an electron away from a neutral position, this original location is now missing one negative charge. There is now one too many positive charges at this location, and the net charge is positive.

The new location of the electron was neutral before the electron came. This location now has one extra unbalanced electron and has a negative net charge.

As mentioned before, too move this electron required energy, since you are moving it out of equilibrium. It wants to go back to equilibrium - that is, a negatively charged electron is attracted to a positively charge location. Whenever you create a path for this electron to move back to the positively (or any other positively) charged location, this electron takes the trip and moves there.

According to the amount of negative charge you have build up (which has got to do with how much energy you have put into your shoe-vs-carpet rubbing), the larger the electric "shock" will be, since more charge is moving.

• So it's not that the carpet is pulling electrons from my shoe, or that the electrons in my shoe are eagerly jumping to the carpet. Actually, my rubbing action is forcing the electrons away from where they really want to be! What if I made something with a positive charge touch the carpet instead of me? would I still be in for a shock later in the day when I touched something else with a positive charge? – Luke Feb 9 '15 at 19:29
• @LukeP Actually, my rubbing action is forcing the electrons away from where they really want to be! Exactly. Some materials are easier to rip electrons off from and some easier to deliver them to. But the force and energy must be externally provided - for example by you. – Steeven Feb 9 '15 at 19:39
• @LukeP What if I made something with a positive charge touch the carpet instead of me? would I still be in for a shock later in the day when I touched something else with a positive charge? The point is not you (your shoe) or the carpet. The point is charge difference. Yes, in the case you set up, the carpet would be discharged, and go back to neutral net charge. But you would still be shocked if you made a path from your shoe, through yourself and into something else with a negative charge. Because you still carry a positive net charge. – Steeven Feb 9 '15 at 19:42
• That's what i thought thank you for your explanation, you have made it clear. (I actually meant to say "negative charge" at the end of my last comment, but got mixed up) – Luke Feb 9 '15 at 20:07