Saturday, April 17, 2010

Electrons: Is there Anything They Can't Do?

When Ben Franklin went out in a thunderstorm and flew his kite, he knew he wanted to capture the power of lightning, but he didn’t know what lightning was made of. He had no idea about ions or electrons. He wanted to prove that lightning was a form of electricity. But he didn’t know what electricity was. But he was the first to recognize that it consisted of positive and negative charges.

A hundred years later, Thomas Edison still knew nothing of electrons, but that didn’t keep him from inventing devices that put them to good use. His electric light bulb, for example, used the flow of electrons in a wire to create a bright glow. The glow is caused by the intense heat produced by the resistance in the wire to the flow of electrons through it.

An electron is the negatively-charged particle that orbits the nucleus of an atom. The nucleus consists of positively-charged protons and neutral neutrons. Electrons have almost no mass. But because they orbit far from the atomic nucleus, they sometimes are able to escape their atomic home and flow freely through the environment. A flow of electrons en masse is what we call electricity.

The flow of electrons is called an electric current. And since Edison’s time, humans have learned how to control and manipulate that flow of electrons in order to accomplish things that neither Franklin nor Edison could have imagined.

We have learned that electrons can be made to move in a wire by exposing that wire to a moving magnetic field. We have also learned how to extract electrons from a chemical reaction, which is how we get batteries. Once electrons are set into motion in a wire, we can do all kinds of beneficial things with them.

One of the simplest things we can make electrons do is produce heat, by sending them through a wire or element that resists their flow. This is useful if we want to produce heat to cook with or to heat our homes. When heat is produced, light can also be produced, since both light and heat are radiation in different parts of the same electromagnetic spectrum. Edison’s challenge was to find a material that would get white hot without losing physical integrity. He found it in the element tungsten.

But electrons can do so much more than produce heat and light. Electrons, since they react to a magnetic field, can also be made to produce a magnetic field. And since magnets can be used to attract certain metals, electromagnets (magnets made by running electrons through a coil of wire) can be used to make metallic wheels spin. Arranging these wheels in a manner that causes them to do beneficial work makes an electric motor.

Using semiconducting elements such as gallium, arsenic, and silicon, we have learned how to control the flow of electrons. We can manipulate the flow of electrons using what are called logic gates. These are similar to switches that allow electrons to flow when turned on or stop the flow when turned off.

By arranging a series of logic gates in complex ways, and by assigning a value such as 1 or 0 to the output, we can use the logic gates to perform any mathematical function. This is the basis for how computers work.

When electrons jump around in an atom, going from one energy level to another in their orbits, they either absorb light or emit it. By causing electrons to absorb energy and then release it at a certain frequency, we can produce specific colors of light. This is how we get light-emitting diodes, or LEDs. We can also use LEDs to produce laser light.

We have learned how to use semiconductors to control how electrons respond to light. In a digital camera, for example, the light that enters the lens strikes an electronic component called a charge coupled device (CCD) or complementary metal oxide semiconductor (CMOS). Photons of light striking either of these devices set electrons in motion in a particular way. This causes an electric charge which can be transmitted out of the capturing device and saved as a picture element (pixel) of a digital image.

Over the past 100 years we have tamed the electron and made it out slave. From the humble beginnings of electric circuits used only to produce light or heat, we now can manipulate the flow of electrons in many ways. We still depend on the flow of electrons to produce our artificial light and in some cases to cook our food and heat our homes. But now electrons do so much more for us.

We rely on them to provide our entertainment by running our television sets, video games, DVD players, and music devices. We also rely on them for our global communication needs. The precise control of electrons within a circuit runs our computers and our cell phones.

In fact, it would be difficult to imagine living in a world without the manipulated flow of electrons. Is there anything they can’t do?

No comments: