How does AC differ from DC current?

The ancient Greeks knew that electricity  existed in nature. They were fascinated by static electricity in amber, but they never guessed the mighty power of this giant force. The invisible giant was not tamed and put to work until the last century. As people worked with electricity and tested it they found two kinds of current   alternating and direct. AC and DC are short for alternating current and direct current.

It is always a thrill to see a row of tall pylons marching across the land, carrying electric power from a might fit' generator. The power lines supported by the pylons carry enough electricity to supply a city, maybe 230, 000 volts. This much power would burst the airing system of an ordinary house. It would electrocute a person corning within a foot of a switch and start fires all over the house.

This high voltage power must be stepped down for general use and the job is done by transformers. But transformers cannot step down DC, or direct electric curront. They can work only with AC, alternating current. This is one reason, when our power systems were being set up, that AC was chosen to carry the electricty and DC is not in common use.

Electric current is moving electrons in a circuit of copper wires. The jolt which starts the electrons moving is called voltage and voltage is supplied at the generator. Here, thp current is given a push and the pressure sends it clear around a loop of wires running from the generator and back again, The two sides of the loop are the two threads of copper you find inside every length of electric wiring.

In direct current, now not in widespread use, the electons in the copper all move in the same direction. In alternating current, they jog together back and forth, first in one direction, then in the opposite direction. In AC, each step back and forth is called a cycle, A 60 cycle current ,jogs back and forth 60 times a second. The busy electrons, hopping back and forth run our toasters and vacuum cleaners. To keep an ordinary light bulb burning, about three billion, billion electrons are kept busy jogging back and forth 60 times a second.

AC came into general use about 60 years ago, when transformers were needed to step down the power brought from the generators. Another reason for the choice of alternating current was in the generator itself

We can make a bigger and more powerful AC generator. It can supply enough power for half a million people and it would take 100 DC generators to make the same amount of electric current.