Direct and Alternating Current

All useful generators of electricity come in two basic forms, alternating current and direct current. Direct current (dc) comes from generators that do not change in polarity, always producing a positive charge. In alternating current (ac) the polarity of the terminals is always changing from positive to negative. Thus you are left with alternating current flow. There are different ways of measuring and generating alternating and direct current.

Direct current only flows in one direction in a circuit. Because the polarity of a direct current voltage source is always the same the flow of current never changes direction. Batteries are one of the more common direct current voltage sources. Batteries are good because their voltage is fixed as well as their polarity. Direct current dose not always need to a constant voltage but it must always stay traveling in the same direction. There are such direct currents called varying and pulsating that change value but not direction.

Alternating current is always changing in direction and amplitude. The current flow in alternating current changes in even intervals. Ac usually changes in power and direction. The vast majority of power supplied for households and big business is alternating current. This is because of the ease of generating alternating current in alternators. The main concept of alternators is moving a conductor through magnetic lines. The change in the magnetic field around the conductor or vice versa makes electrons move. When you have physically moved either the conductor or magnet in a complete 306-degree circle you have produced one sine wave or one complete cycle. The amount of time it takes to complete one cycle is referred to as a period.