The electric constant () is the permittivity of vacuum, a physical constant, defined by: Permittivity is an intensive physical quantity that describes how an electric field affects and is affected by a medium. ... For other uses, see vacuum cleaner and Vacuum (musical group). ... In science, a physical constant is a physical quantity whose numerical value does not change. ...

where:

μ₀ - magnetic constant

c - speed of light

In SI units, the value is exactly expressed by: Cherenkov effect in a swimming pool nuclear reactor. ... The International System of Units (abbreviated SI from the French language name Système International dUnités) is the modern form of the metric system. ...

= 2.781 625 140 131 510 166 480 1 · π^-1 · 10^-11 F / m

The farad (symbol: F) is the SI unit of capacitance. ... The metre (Commonwealth English) or meter (American English) (symbol: m) is the SI base unit of length. ...

References

• NIST - CODATA 2002 recommended values - electric constant. URL accessed on August 31, 2005.