Electricity is most easily explained by the electron theory, developed in the early 20th century. The electron theory, in turn, depends on the atomic theory of matter.

Electron Theory

The center, or nucleus, of an atom contains one or more particles called protons. A proton has a type of electric charge said to be positive (+). Circling the nucleus are one or more electrons. An electron has a type of charge said to be negative (-).

An electrically neutral atom has one electron for each proton. In such an atom, the positive and negative charges exactly balance. An atom may lose or gain one or more electrons, leaving it with a net positive or negative charge. A charged atom is called an ion.

Electric Field

An electric charge brought near one or more other electric charges will experience an electrical force. One of the fundamental laws of electricity is that like charges (either positive or negative) repel each other, and unlike charges attract each other. The region in which a charge experiences an electrical force is called an electric field.

Electric fields consist of lines of force and indicate the path that a positive electric charge follows in the field, and normally radiate from or converge on the charged body. Electrically charged bodies — objects in which there is a net electric charge — exert forces on each other at a distance by means of their electric fields.

When the atoms that make up an object lose or gain electrons, the object acquires a net electric charge. An object with a positive charge tends to attract electrons; one with a negative charge tends to repel them.

An electric current exists when there is a net flow of electrical charge. An electric current (flow of charge) has energy that can be converted to heat, light, or used to perform mechanical work as in an electric motor.

An electric current in a metal wire consists of the movement of electrons from a negativey charged region to a positively charged one. The currents used in everyday electrical devices involve the movement of very large numbers of electrons. For example, every second that a lightbulb is on, some billion billion electrons enter (and leave) the lightbulb filament. Although the individual electrons forming a current move through a wire slowly (typically less than 5.5 inches per hour [14 cm/h]), the force of repulsion between the electrons travels at nearly the speed of light.

Conductors and Insulators

Electric charges can flow much more easily through some materials than others. A material that has very little resistance to the passage of an electric current is called a conductor. In general, metals are very good conductors, because their atoms contain one or more loosely bound electrons. These electrons are free to move and form part of an electric current. At room temperature, silver offers the least resistance to an electric current followed by copper, gold, and aluminum. A liquid that permits the flow of positive and negative ions is called an electrolyte. An important use of electrolytes is in batteries. Under certain conditions, some materials—called superconductors—have no resistance to an electric current.

Some materials offer a very large resistance to the flow of electric charges. Such a material is called an insulator, or dielectric. Some common insulators include glass, rubber, porcelain, paraffin, mica, and dry air. Insulators are important in the use of electricity because they will confine an electric current to the conductor intended to carry it. For example, wires are usually covered with insulation to help prevent electric charges flowing in the wire from escaping to surrounding materials.

How Electricity Works In Our Homes

One of the most useful properties of electricity is its ability to produce heat and light. Electricity produces heat in a conductor as it overcomes the conductor's resistance to the flow of electrons through it, just as mechanical energy produces heat in overcoming friction. The heat-producing effect of electricity is used in electric ranges, toasters, soldering irons, and many other devices. In incandescent lightbulbs, the effect is used to make a filament glow brightly.