# farad (F)

Farad (F) is the derived unit of electrical
capacitance in the SI system of units.
One farad (F) is the capacitance of an electric capacitor between the two plates of which there appears a difference of electric potential
of one volt when it is charged by a quantity
of electricity equal to one coulomb (*F* = *C*/*V*). The unit is named after the British
scientist Michael Faraday.

One farad is an exceptionally large capacitance: the entire Earth, considered
as a spherical conductor of radius 4,000 miles, has a calculated capacitance
of only 0.0007 farad. Capacitances that are actually encountered are expressed
in **microfarads** or **picofarads**.