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Physical Measurement Laboratory

Office of Weights and Measures

SI Units – Electric Current

Resources for Students and Teachers | League of SI Superheroes – Ms. Ampere

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 ∆ν_Cs.

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.

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 are 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:

IEEE Global History Network
University of St. Andrews, Scotland

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:

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Resources for Students and Teachers

Teachers: Top 10 Tips for Teaching the Metric System. (NIST)

Not sure how to tell that scientific minded person in your life how you feel? Maybe our Superhero Valentine's Day cards will do the trick.
Download these fun coloring pages for Mrs. Ampere and our SI Superheroes.
The Metric Meal (option 2) (NIST) focuses exclusively on length measurements and uses a multidisciplinary approach to build measurement skills.

League of SI Superheroes - Mrs. Ampere
- This comic book-style video animation series has been developed to help middle school students learn about the 7 SI base measurement units.
SI Units Card Deck (SP 1297) (NIST) - This activity offers a fun way to enhance understanding of the International System of Units.

SI Units Card Deck (SP 1297) (NIST) - This activity offers a fun way to enhance understanding of the International System of Units.
SI Base Units Relationship Poster (SP 1247) (NIST) - A colorful poster illustrating the relationships of the International System of Units (SI) derived units with special names and symbols and the seven traditional base units.
How Do Smoke Detectors Work? (NIST) - Find out how smoke detectors measure particles in the air to sense danger. Click the link to learn how they help keep us safe.

SI Units Card Deck (SP 1297) (NIST) - This activity offers a fun way to enhance understanding of the International System of Units.
SI Base Units Relationship Poster (SP 1247) (NIST) - A colorful poster illustrating the relationships of the International System of Units (SI) derived units with special names and symbols and the seven traditional base units.
Ampere's Law (TeachEngineering, Grade 12) - This lesson introduces students to Ampere’s Law and its applications in calculating magnetic fields around current-carrying conductors, with connections to technologies like MRI machines.
Ohm’s Law (PhET Interactive Simulations) - This interactive simulation allows students to explore Ohm’s Law by adjusting voltage and resistance to see how current changes in a circuit, helping them understand the relationship between voltage, current, and resistance.
History of NIST Quantum Voltage Standards (NIST) - In the 1970s, scientists developed a new way to measure voltage very precisely using special materials and tiny electrical parts called Josephson junctions.

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"A is for Ampere" - Circuit Playground Episode 1! Learn all about electronics with Ladyada, ADABOT and special guests!

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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.