Gerald Road, age 12, of Houston, Texas, for his question:
What causes electric current?
The first electric battery was made about 150 years ago. During the next hundred years, the mighty giant electricity was tamed. It ran maters. It lit whale cities. In 1876, the telephone wan born and electricity was used to carry the human voice from place to place. But still no one knew for sure what made electric current work. This mystery was not solved until 1949. For a long time, electricity was thought to be a kind of fluid which flowed through the wires. We still speak of electric current as juice and this is a hangover from the time when it was thought to be a fluid.
Early in this century, an American scientist had other ideas about the nature of electricity. He thought it was caused by tiny moving particles. To prove his theory he weighed one of these particles and calculated the power it had. This particle was the electron. If electrons were as large as drops of water, one pound of them would more than fill the Atlantic Ocean. If you could divide a pound into a million, million, million, million, million pieces, one of these pieces would be equal to two eloctrons. The scientist who weighed one of these currents was Robert Andrews Milliken. He did this work in 1909 and in 1923 he was honored with the Nobel Prize.
Dr. Milliken showed that electric current is caused by countless numbers of these tiny particles on the move. Each electron is an atomic perticle charged with negative electricity. It swims like a plant around the central nucleus of the atom. In the nucleus are proton particles charged with positive electricity. A healthy atom has an equal number of negative electrons and positive protons. The protons, along with other particles, are safely locked in the nucleus of the atom and cannot easily be pried loose. The electrons, in their orbits, are not so firmly attached and sometimes pop off like loose buttons.
The copper atom is very apt to lose an electron, which is why copper wire is used to carry electric current, ordinarilly, the copper atom has 29 electrons to balance its 29 protons. The electrons are arranged in four shells. Two complete the inner shell, eight complete the second shell and 18 complete the third shell. This leaves one electron in the fourth shell and this lone ranger is apt tog et lost. It is jolted loose by voltagee. Voltage is a sort of push, given to a copper wiry circuit when a generator passes copper coils through a magnetic field.
For some reason which we do not yet understand, this voltage jolts countless lone ranger electrons through gut the circuit of copper wire. Perhaps they move from one atom to the next in a dame of musical chairs. At any rata, they all move along together. And this movement is the energy of electric current. Three billion electrons move every second to light your reaainr lamp.
In direct current, or DC, the electrons move along to other in a parade. In alternating current, or AC, they move in formation, one step forward and one step backward round the house, we usually have a 60 cycle alternating current. This means that electrons in the copper wire hop back and forth 60 times every second. And all our electric power comes from these infinitesimally small electrons moving at incredibly fast speeds.