# Electric Current

## Current Flow Vs. Electron Flow

We cannot directly observe the electrically-charged particles that produce current. It is usually not important to know whether the current results from the motion of positive or negative charges. Early scientists made an unfortunate choice when they assigned a positive polarity to the charge that moves through ordinary wires. It seemed logical that current was the result of positive charge in motion. Later it was confirmed that it is the negatively-charged electron that moves within wires.

The action of some devices can be explained more easily when the motion of electrons is assumed. When it is simpler to describe an action in terms of the motion of electrons, the charge motion is called electron flow. Current flow, conventional current, or Franklin convention current are terms used when the moving charge is assumed to be positive.

Conventional current flow is used in science almost exclusively. In electronics, either conventional current or electron flow is used, depending on which flow is most convenient to explain the operation of a particular electronic component. The need for competing conduction models could have been avoided had the original charge-polarity assignment been reversed.

## Resources

### Books

Hewitt, Paul. Conceptual Physics. Englewood Cliffs, NJ: Prentice Hall, 2001.

Hobson, Art. Physics: Concepts and Connections. Upper Saddle River, NJ: Prentice Hall, 1994.

Ostdiek, Vern J., and Donald J. Bord. Inquiry Into Physics. 3rd ed. St. Paul, MN: West Publishing Co., College & Schl. Div., 1995.

Donald Beaty

## KEY TERMS

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Conventional current

—Current assuming positive charge in motion.

Coulomb

—The standard unit of electric charge, defined as the amount of charge flowing past a point in a wire in one second, when the current in the wire is one ampere.

Frequency

—Number of times per unit of time an event repeats.

Hertz

—A unit of measurement for frequency, abbreviated Hz. One hertz is one cycle per second.

Picoampere

—One trillionth of an ampere or 10–12 amperes.

Speed of light

—Speed of electromagnetic radiation, usually specified in a vacuum. Approximately 6.7 × 108 miles per hour (3 × 108 meters per second).