# Henry (unit)

Physical unit
Unit name Henry
Unit symbol ${\ displaystyle \ mathrm {H}}$ Physical quantity (s) Inductance
Formula symbol ${\ displaystyle L; \, M}$ dimension ${\ displaystyle {\ mathsf {M \; L ^ {2} \; T ^ {- 2} \; I ^ {- 2}}}}$ system International system of units
In SI units ${\ displaystyle \ mathrm {1 \, H = 1 \; {\ frac {kg \, m ^ {2}} {A ^ {2} \, s ^ ​​{2}}} = 1 \; {\ frac { Wb} {A}} = 1 \; \ Omega \, s}}$ Named after Joseph Henry
Derived from Volts , seconds , amps

Henry is the unit of inductance in the SI system of units and is named after Joseph Henry . It is specific to each conductor coil and is usually indicated on it.

${\ displaystyle 1 \, \ mathrm {H} = 1 \, \ mathrm {\ frac {V \, s} {A}} = 1 \, \ Omega \, \ mathrm {s}}$ A coil has an inductance of 1 henry if a self-induction voltage of 1  volt is produced with a uniform current change of 1  ampere in 1  second .

## CGS system of units

The Abhenry (abH) is the outdated unit of measurement for inductance from the electromagnetic CGS system of units . It applies

1 abH = 10 −9 H = 1 nH (nanohenry)

In an inductance of 1 abH, a current increasing by 1 Abampere per second generates a voltage of 1 Abvolt .

The stathenry (statH) is the outdated unit of measure for inductance from the electrostatic CGS system of units . It applies

1 statH = c 2 · 10 −5 H ≈ 8.98755 · 10 11 H ≈ 899 GH (Gigahenry)

In an inductance of 1 Stath to a 1 generates Statampere increasing per second current is a voltage of 1 statvolt .

## history

Before the introduction of the SI , today's SI Henry was referred to as the absolute Henry , while the Henry , which was derived from the definition of the (international) ohm at that time, was called the international Henry . Since the national standard authorities had determined different conversion factors based on the measurement regulations of the definitions, there were nationally different numerical values ​​for the international Henry. The International Committee for Weights and Measures put 1946 firmly the average international ohms with 1.00049 Ω, which also applies:

1 medium international henry = 1 H int = 1,00049 H

The American international Henry was also significant:

1 U.S. International Henry = 1,000495 H.

The Henry was formerly also known as the quadrant , since 1 Henry also corresponds to the dimension according to the length of an earth quadrant of 10 9 cm.