Carma Houghton: age 12, fromm Brigham Young, Utah, for her question:
Wtat is the difference between AC and DC?
The first electric current was DC ‑ direct current. It was put to use long before arnbody knew what caused electric current. People thought it was a mighty, magic juice that flowed like hot water through the wires. Then it was discovered that electricity is caused by moving eledtrons.
No one has ever seen an electron. It is far too small even to be photographed by the most powerful microscope. Nevertheless we know a great deal about these tiny bundles of electricity, We don't know all about them but we can make the work for us.
The electron is part of the atom. An atom may have one or ninety or more electrons depending on the kind of atom it is. Most electrons are buttoned onto‑, their atoms very securely. But‑ certain atoms have ‑electrons that are rather like loose buttons, The copper atom has one of these loose button electrons, Too much exertion and the copper atom loses its outside button,
However the copper atom does not like to lose a button any more than you do. If it is in the copper wire that we use to tote electric current it is near another copper atom. The same exertion jolts loose its neighbor's button also, So there are plenty of loose buttons flying around, .And every lopsided copper atom tries to grab one, In this way the loose electrons are passed along from ore copper atom to another, If the powerful exertion keeps ups the exchange of buttons goes on at a great rate. Billions of electrons are moving along the copper wire and their activity gives us the electric current,
The exertion which causes it all is called voltage. This jolt may be given to the copper wire by chemicals, heat or magnetism, The voltage for our electric wires comes from giant generators using movement and magnetism. It lines up the little electrons and sets them all hopping in, the same direction.
In direct currents, electrons move around the wire circuit in one direction.
In alternating current, they all move one step forward and one step backward. Each step forward and back is called a cycle, Most of our household gadgets are fixed to work on AC of 60 cycles. That means that those tiny electrons in the wire move back and forth 60 times each and every second. And three billion billion of them are on the job to keep your reading lamp shining every second.
Nowadays, most of our current is AC, This current is easier to make, One big generator can do the work of 100 dynamos making direct current. It is also easier to carry from place to place. Maybe nearly a quarter of a million volts of power are carried from the generator to a city. This power must be stepped down for home or factory use. The job is done by a simple little gadget called a transformnd a transformer will not work for DC.