Electrical elastance is the inverse of capacitance. The SI unit is the reciprocal farad. Although the term daraf is sometimes used, this is not approved by SI. Electrical inductor-capacitor-resistor circuits can be converted to mass-spring-damper systems. If voltage is taken to be force and current velocity, elastance corresponds to the elastic constant of a spring.

SI electricity units

SI electromagnetism units
Name	Symbol	Dimensions	Quantity
ampere (SI base unit)	A	C / s	Current
coulomb	C	A · s	Electric charge, Quantity of electricity
volt	V	J / C = kg m2 / (s2 C)	Potential difference
ohm	Ω	V / A = kg m2 / (C2)	Resistance, Impedance, Reactance
ohm &middot metre	Ω &middot m	kg m3 / (C2)	Resistivity
farad	F	C / V = C2 s / (kg m2)	Capacitance
farad per metre	F / m	C2 s / (kg m3)	Permittivity
reciprocal farad	F−1	kg m2 / (C2 s)	Elastance
siemens	S	Ω−1 = C2 / (kg m2)	Conductance, Admittance, Susceptance
siemens per metre	S / m	C2 / (kg m3)	Conductivity
weber	Wb	V &middot s = kg m2 / (C s)	Magnetic flux
tesla	T	Wb / m2 = kg / (C s)	Magnetic flux density
ampere / metre	A / m	C / (s m)	magnetic induction
ampere-turns / weber	A / Wb	C2 / (kg m2)	Reluctance
henry	H	V &middot s / A = kg m2 s / (C2)	Inductance
henry per metre	H / m	kg m s / (C2)	Permeability
(dimensionless)	-	-	Magnetic susceptibility

See also

• harmonic oscillator