Basics of Electricity
by Ron Kurtus (revised 6 December 2013)
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 is electricity that is "static" or not flowing. It consists of negative (−) or positive (+) electrical 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 electrical insulator.
(See Electrical Charges for more information.)
Attraction and repulsion
When two objects with a collection of static electrical charges on their surface are brought in proximity, they will attract each other, provided their electrical charges are opposite. If the potential difference between the charges is sufficient, a spark may even fly between the objects. If the electrical 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.
(See Basics of Static Electricity for more information.)
DC and AC electricity
Free electrons will flow through a conducting material such as a metal wire when there is an electrical 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 electrical charge.
Electrons flow toward positive charges in wire
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.
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.
Uses and advantage
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 electrical charges to attract the particles. Likewise, positive ions will flow if there are negative electrical charges to attract the particles. As the number of atoms or molecules increase in the space between the electrical charges, the resistance to electrical flow increases.
The most common place that you experience the flow of electrical charges in a vacuum or near-vacuum is in a television picture tube or cathode ray tube (CRT). To a degree, this type of electrical 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.
Cathode ray tube
A cathode ray tube (CRT) has most of its air removed. A filament that is heated white hot gives off electrons. A negative charge is also applied to the filament or cathode to accelerate the electrons away from it. At the other end of the neck of the CRT is a series of plates that are given a positive electrical charge. This accelerates the electrons toward it. The plates are called anodes.
Variations in their charges can direct the beam of high speed electrons, as they move past and smash into the television or CRT screen, resulting in flashes of light.
The beam of electrons is called a cathode ray, a name given years ago when the phenomenon was discovered.
A fluorescent lamp is a tube where the air has been removed and replaced with a small amount of an inert gas such as Xenon, along with a trace of Mercury. The pressure inside the lamp is about 0.3% of atmospheric pressure, so it is essentially a partial vacuum.
The ballast or cathode heats and ejects electrons which travel toward the anode or positive charged terminal
Storms on the surface of the Sun give off streams of electrically charged particles. These electrons and ions speed across the vacuum of space until the reach the Earth's atmosphere. The electrically charged particles are attracted to the magnetic north and south poles. Collisions with air molecules results in lights that can be seen across the sky over the poles.
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
How Electricity Works - Animated guide
Electrons in Metal Simulation - From the University of California in Santa Cruz
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