Amping up the Enlightenment

It is a truth universally acknowledged….that chemists avoid physics and physicists avoid chemistry. Of course, I’m not saying that scientists are devoted only to their field of expertise and prejudiced against all the others. We’d know a whole lot less about the world if that were the case. I think it’s safe to say that people of all backgrounds like to stick to what they know, whether it’s philosophy or physics.

From: xkcd.com

Unfortunately for scientists, there is an inconvenient amount of overlap between areas of research. This overlap makes communication between biologists, chemists, physicists, etc. absolutely essential. So, in that spirit, let’s venture into the dangerous no-man’s land that is physical chemistry. Physical chemistry (or “p-chem”, if you’re a super hip college student), is, “the branch of chemistry concerned with the interrelation of the chemical and physical properties of matter and the application to chemical systems of the principles of physics (in thermodynamics, kinetics, electricity, spectroscopy, etc.).” Or, in normal-people words, it’s a study of how and why atoms work, and how that knowledge can be used to make things like computers and efficient engines.

I’ve suspected for a while that the physics I’ve been learning is actually chemistry (though the physicists would say that the chemistry I’ve been learning is actually physics). My suspicions were confirmed when I visited the Franklin Institute in Philadelphia, and they had a whole room devoted to explaining electricity. This was really awesome, since we’ve been learning all about electricity in physics class. But I thought that electricity was exclusively physics…..

Yet, lo and behold, there were a number of diagrams…of atoms. As it turns out, electric charges are the result of atomic structure. Atoms are made of positively charged protons, negatively charged electrons, and neutral neutrons. Protons sit in the middle of an atom with the neutrons (composing the nucleus), and the electrons zoom around this dense center, forming an “electron cloud”. Being an electron’s like riding the teacups at Disney World forever, except without tracks and in fast-forward. Atoms are held together by the attraction between the negatively charged electrons, and the positively charged nucleus (just like the opposite poles of magnets stick together). The charge on these particles is inherent, meaning that electrons and protons have charge by virtue of being electrons and protons, just like you’re however old (young?) you are because you’ve lived for that many years.

This is a basic diagram of an atom, with protons, neutrons and electrons labeled.

If an atom loses an electron, it becomes positively charged. If an atom gains an electron, it becomes negatively charged. Atoms don’t lose protons. I’ve always wanted atoms to become more positive because they gain protons, but it just doesn’t work that way. This idea of atomic charges becoming more or less negative applies to whole objects, too. This time of year, everyone starts getting static shocks, because there’s less moisture in the air. Shocks from your sweaters, your car, door knobs, and so forth. The Franklin Institute actually had a sign at the entrance to the electricity exhibit warning people that some of the interactive displays could generate painful shocks. People touched them anyway, of course, and then laughed about it while getting their friends/children/spouses to “learn” about static electricity.

Some atoms want to get rid of an electron, and some want to have more electrons, all in the pursuit of stability. Everything from people to buildings to atoms is happiest when stable. As a result, sometimes atoms let go of their electrons. Sometimes atoms want to get rid of their extra electrons so badly, the electrons actually jump from one material to another. It’s like carrying groceries into your house, and you’re struggling with three heavy bags, but the person who was riding shotgun is bringing the eggs inside. You want to give them one of your bags, and they (assuming they have a conscience) want to take one from you because they feel guilty about not helping. Without ever actually touching each other, you transfer a bag as quickly as possible, hoping no one spills the milk. This is basically what happens when a positively charged material comes near a negatively charged material. The negatively charged material has an excess of electrons, and really, really wants to donate some of those electrons as soon as possible (if only people were so eager to make donations!). This jumping between positively and negatively charged materials is how you can get a shock from a door handle before you actually touch it.

Since we’re on the subject of static electricity (which can be a bit of a bore since there’s really nothing shocking to learn about it), I think it’s worth shifting topics slightly to talk about how electricity is generated in those wind-up flashlights. I learned about this by accident one afternoon while studying in the physics office in the basement of the science building (i.e. my secondary address). My professor was building an experiment on the table I was working at (because that’s what professors do when they’re not teaching class- devise ways to challenge (torture?) student in lab). The experiment involved those flimsy plastic race track pieces and, naturally, a little Hot Wheels car with a magnet attached. It also involved a bunch of copper wires through which the track went, all attached to a multi-meter, which reads how much voltage or current is generated in a current. As it turns out, you can actually create an electric current by passing a magnet quickly through a bunch of wires, which totally blew my mind. So, when you’re cranking the, uh, crank on a wind-up flashlight, you’re pushing a magnet through a coil of wire over and over to generate electricity to light up the bulb. There’s no Hot Wheels car inside the flashlight, although that would be pretty cool….

So, maybe you’re wondering how the heck a magnet running through some wire can create electricity. I certainly was. This method of generating electricity is called induction, and was discovered by Michael Faraday in 1831. We named the Farad after him. Magnets create magnetic fields, which is like the area that’s affected by the magnet, like how the iron filings are affected by the magnet in this picture:

The movement of the magnet and its field creates an electric field in the coil because the magnetic field pushes and pulls electrons (and there are a lot of them in a wire) until a current starts flowing.

Faraday's Electromagnetic Lab

Click to Run

The electromagnetic force causes this push and pull, and we wouldn’t have generators in our houses or power plants  (or more importantly, wind-up flash lights) without it.

I’ll stop here, before I get ahead of myself by attempting to cover an entire semester of physics with one blog post.

Did I say physics? I meant chemistry.

Leave comments if you have questions- I know this post got a little technical.

-Ashley

Oh, and a little more Bill Nye before you go:

Sources: Physics for Scientists and Engineers: A Strategic Approach by Randall D. Knight (Volume 4, 3rd Edition)

One comment

  1. Hank Yochum says:

    Great blog about PHYSICS!!!!

    Love that you included the PhET simulation…