|  |  | Summary

This chapter provided you the basic theory of electricity and the factors which affect data transmission. More specifically, you learned that:

- e lectricity is based on the ability of electrons of certain types of atoms to separate, or flow, from the confines of these atoms
- o pposite charges attract and like charges repel. Electricity flows from negative to positive within electrical circuits
- m aterials can be classified as either insulators, conductors, or semiconductors, depending on their ability to allow electrons to flow
- t he concepts of voltage, current, resistance, and impedance provide a means of measuring electricity which is required to be able to design and manufacture electronic devices
- a lternating current and direct current are the two types of current. AC is used to provide power to our homes, schools, and work places. DC is used with electrical devices that depend on a battery to function
- e lectrical grounds provide a baseline from which to measure voltage. They also are used as a safety mechanism to prevent hazardous shocks
- a ll electronic equipment is composed of electrical circuits that regulate the flow of electricity via switches

The next chapter discusses the different types of networking media that are used at the physical layer. In addition, it describes how network devices, cable specifications, network topologies, collisions and collision domains can help determine such things as how much data can travel across the network and how fast.