Skip to main content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

SI Units - Electric Current

A - Ampere - Electric Current - 2018

The ampere is defined by taking the fixed numerical value of the elementary charge e to be 1.602176634 × 10−19 when expressed in the unit C, which is equal to A s, where the second is defined in terms of ∆νCs.

The SI unit of electric potential difference is the volt (V) 1 V = 1 W/A.

The SI unit of electric resistance is the ohm (Ω). 1 Ω = 1 V/A.

lightbulb

When spelled out in full, unit names are treated like ordinary English nouns. Thus the names of all units start with a lower-case letter, except at the beginning of a sentence or in capitalized material such as a title. In keeping with this rule, the unit symbols for Ampere is a capitalized "A" and Volt is capitalized "V" because both unit names are based on the names of scientists. 

Andre Marie Ampere (1775 - 1836) Name endures in everyday life in the ampere, the unit for measuring electric current. These biographical website can help you learn more:

Count Alessandro Volta (1745 - 1827) Name endures in everyday life in the volt, the derived unit for measuring electric potential and also the inventor of the first battery. These biographical website can help you learn more:

For Students and Teachers

ampere_front_web
League of SI Superheroes – Ms. Ampere

This comic book-style video animation series has been developed to help middle school students learn about the 7 SI base measurement units. Ms. Ampere has a shocking amount of power over the flow of electrons—electrical current. In practical terms, an ampere is the measure of the flow of electrons past a point—about 6 quintillion electrons (that's a 6 followed by 18 zeros!) per second.

Contacts

Created June 21, 2011, Updated November 15, 2019