THe difference between ac and dc

Alternating Current (AC)

Alternating current can travel efficiently through wires making it useful for power plants or any other form of large power supplier.  Its ability to travel efficiently is due to the way it moves.  If you were to look at the movement of an alternating current on a graph it would look as if it were a sine curve.  The upward humps resemble the current traveling in an upwards direction and the downwards hump is the current traveling in the opposite direction.  The reason AC is used more in todays world is it ability to transport high voltages into households.  The device that makes this work is the transformer which is basically two loops of wire spread apart a specified distance.

Direct current (DC)

Direct current has a linear motion, if it were to be plotted on a xy-graph it would be a line.  An example of DC current is a battery that has a negative and positive terminals.  The electrons can only move from the positive terminal to the negative, there is no reversal of direction that allows the electrons to travel the opposite direction.  DC current may not be very effective in transferring large voltages of electricity, but it is efficient at low voltages.  Only smaller devices that take small amounts of voltage use direct current to energize.