Carol Siwanick, age 9, of Scarboro, Ont., Canada, for her question:
What is in a current of electricity?
Maybe you have a friend who is 90 years old. If so, he can tell you about the first electric street lights. This happened when your friend was as old as you are now. Electric current was put to use in all sorts of ways. But no one knew what made it work for another 30 years. Your old friend was 50 before science learned what makes an electric current.
When the electric wiring goes wrong, we send for an electrician. When the job is done, he may tell you that the juice is now flowing again in the wires. You can turn on the lights and expect the refrigerator to start up and freeze the popsicles. But if you think that the electric current flows through the wires like a fluid juice, you have the wrong idea.
Something moves in the copper wiring, but it is not a flowing fluid. The current is caused by atomic particles which are far, far too small for our eyes to see. The midgets are electrons, and the number of them in one pound is five followed by 29 zeros. Each electron is just like all its brothers. As a rule, it belongs to an atom. It orbits the core or nucleus of the atom much as the earth orbits around the sun.
Electric wiring is made from copper, and the shiny metal is made from countless copper atoms crowded together. Each copper atom has the right to 29 electrons. These swarming particles are arranged in neat rings around the nucleus of the atom, with so many electrons in each ring. The inside ring or shell has two electrons. The second shell has eight and the third shell has 18 electrons. This leayes one lone electron to start a fourth shell.
Atoms tend to lose some of their electrons, and the copper atom tends to lose the 29th electron in its outer shell. This happens when the electric generator sends a jolt of power called voltage through the wires. The outside electrons from countless trillions of copper atoms leave home. Some hop to the next atoms, some move through the tiny spaces between the copper atoms. But the voltage from the generator makes all these electrons move in the same direction. Electric current is caused by swarrming electrons inside the copper wire, all moving together in the same direction. To keep a reading lamp glowing, three billion billion electrons must move every second.
Our electricity may be dc, which is shorthand for direct current. But it is more likely to be ac, which is alternating current. In direct current, the electrons Keep moving along in one direction. In alternating current, they jog one step Forward and one step back. In the reading lamp, the busy electrons are most likely Jogging back and forth 60 times every second.