# Basics of Electricity

by Ron Kurtus (revised 12 November 2019)

Electricity concerns the presence of electric charges, as well as the flow of those charges as an electric current. Although other subatomic particles can possess an electric charge, we normally consider protons and electrons as the primary charged particles. Protons have a positive (+) electric charge and electrons have a negative (−) electric charge. Most of electricity concerns electrons.

There are three major types of electricity. One type is static electricity, which is the presence of either positive (+) or negative (−) electric charges in or on an object, usually a nonconducting material.

The second form of electricity is the flow or movement of free electrons through a conducting material, such as a metal wire, toward an area of positive electric charges. This current of electrons can be in one direction or direct current (DC) electricity, or it can alternate back and forth as alternating current (AC) electricity.

The third form is the movement of charged particles through a vacuum or near vacuum.

Questions you may have include:

• What is static electricity?
• What are AC and DC electricity?
• How does electricity flow in a vacuum?

This lesson will answer those questions. Useful tool: Units Conversion

## Static electricity

Static electricity is electricity that is "static" or not flowing. It consists of negative (−) or positive (+) electric charges that collect on or near the surface of a material. The negative charges may be free electrons or negative ions. The positive charged particles are positive ions. Usually, the material is a nonconductor or electric insulator.

### Attraction and repulsion

When two objects with a collection of static electric charges on their surface are brought in proximity, they will attract each other, provided their electric charges are opposite. If the potential difference between the charges is sufficient, a spark may even fly between the objects. If the electric charges are the same, the objects will repel.

### Creating static electricity

Static electricity is created when certain materials are rubbed together or pushed together and pulled apart. It can also be caused by electrostatic induction.

## DC and AC electricity

Free electrons will flow through a conducting material such as a metal wire when there is an electric field applied to the wire in the form of a potential difference or voltage at the ends of the wire. The electrons will then flow toward the area that contains a positive electric charge.

Electrons flow toward positive charges in wire

### Direct current

If one end of the wire or conductor has a positive charge over a period of time and the other end has a negative charge, the flow of electricity will be continuous in one direction. The resulting current is then called direct current or DC electricity.

DC electricity can be created by a battery or DC generator.

### Alternating current

If the terminals constantly switch their polarity from (+) to (−) and back again, the direction of the electrons alternates back-and-forth and is call alternating current or AC electricity. This is the type of electricity that comes from the outlets in most homes.

AC requires an AC generator for its creation.

DC is used in many devices that do not require high voltages for their operation, such that batteries are used for power. AC can be used in higher voltages. It has the advantage of being able to have its voltage easily changed to a higher or lower level. AC is required for many electronic devices.

## Flow of charges in a vacuum

Electrons and negative ions will readily flow in a vacuum as a form of electricity if there are positive electric charges to attract the particles. Likewise, positive ions will flow if there are negative electric charges to attract the particles. As the number of atoms or molecules increase in the space between the electric charges, the resistance to electric flow increases.

The most common place that you experience the flow of electric charges in a vacuum or near-vacuum is in a television picture tube or cathode ray tube (CRT). To a degree, this type of electric flow is also seen in a fluorescent lamp. The Sun gives off streams of charged particles that—when attracted to the Earth's magnetic poles—create the Northern and Southern lights.

## Summary

Electricity is the movement of free electrons in a material. It moves the best though metals. Static electricity is the collection of electrons and positive ions on the surface of a material—usually a non-conductor. Direct current electricity moves in one direction and usually is created in batteries. Alternating current electricity is most commonly used in homes and can have its voltage changed to suit the need.

Have an electric smile

## Resources and references

Ron Kurtus' Credentials

### Websites

How Electricity Works - Animated guide

Electrons in Metal Simulation - From the University of California in Santa Cruz

DC and AC Electricity Resources

Physics Resources

### Books

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www.school-for-champions.com/science/
electricity.htm

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