|  | 4.1 | Basics of Electricity
| 4.1.7 | Graphing AC and DC voltage
An oscilloscope is an important, and sophisticated electronic device used to study electrical signals. Because it is possible to control electricity precisely, deliberate electrical patterns called waves can be created. An oscilloscope graphs the electrical waves, pulses, and patterns. It has an x-axis that represents time, and a y-axis that represents voltage. There are usually two y-axis voltage inputs so that two waves can be observed and measured at the same time. Electricity is brought to your home, school, and office by power lines. The power lines carry electricity in the form of alternating current (AC). Another type of current, called direct current (DC) can be found in flashlight batteries, car batteries, and as power for the microchips on the motherboard of a computer. It is important to understand the difference between these two types of current flow.