21. Key SI Units — Quick Reference

Electric charge

Coulomb

C

Electric current

Ampere

A

Potential difference / EMF

Volt

V

Resistance

Ohm

Ω

Resistivity

Ohm-metre

Ω·m

Conductance

Siemens

S

Electric power

Watt

W

Electrical energy (SI)

Joule

J

Electrical energy (practical, household billing)

Kilowatt-hour ('unit')

kWh

Capacitance

Farad

F

Magnetic field strength / flux density

Tesla

T

Magnetic flux

Weber

Wb

Frequency

Hertz

Hz