|  | 8.6 | Planning Structured Cabling: Electricity and Grounding
| 8.6.1 | Differences between AC and DC
Electricity is a fact of modern life. We use it to perform a variety of tasks. It is brought into our homes, schools, and offices by power lines that carry it in the form of alternating current (AC). Another type of current, called direct current (DC), is the kind found in a flashlight, car battery, and in the motherboard of a computer. It is important to understand the difference between these two types of current flow. DC flows at a constant value when circuits are turned on. To see how this works, refer to the Figure . As illustrated, the battery supplies current during a given period of time at a constant level of current flow. AC rises and falls in current values as it is manufactured by power companies. This rise and fall can be explained by the series of graphics shown here: The Figure depicts the rise to peak of current flow as the south pole moves across the core of the coil. The Figure depicts the fall to 0 current flow as the two poles straddle the core and balance current flow to 0 value. The Figure depicts the rise to opposite polarity peak (a negative value) as the north pole moves across the core of the coil. The Figure depicts the fall to 0 current flow as the magnet exits the coil area. AC power as manufactured for delivery to homes uses this concept.