Henry (unit)

Henry is the SI unit of inductance. The unit is named after Joseph Henry. It is specific to each printed circuit coil and is usually provided on it.

The symbol L for inductance was chosen in honor of Emil Lenz, whose theoretical work on electromagnetic induction were fundamental.

A coil having an inductance of 1 Henry, when at uniform change in current of 1 Ampere in 1 second, a self-induction voltage of 1 volt is produced.

If the current change in an elongated ( slim ) head coil, it creates a self-induction voltage U ind, what its cause, current change, counteracts. This special case of conservation of energy is defined by Lenz's law. In this way, the induced voltage is equal to the negative product of the inductance of the coil and the current change.

Derivation of the inductance using the self-induction voltage by amperage change:

Wherein the magnetic flux

Derived here time and is multiplied by the number of turns n of the thin coil. The negative sign arises from the already mentioned Lenz's law, since the induction always counteracts the cause. A positive sign would contradict the conservation of energy, otherwise the energy would be created out of nothing.

This formula takes on the form

Bring. Now the break to the constant L is defined:

Thus, the inductance

CGS unit system

The Abhenry ( abH ) is the obsolete unit of measurement for inductance of the electromagnetic CGS unit system. It is

In an inductance of a 1 to 1 abH Abampere per second increasing current produces a voltage of 1 Abvolt.

The Stathenry ( Stath ) is the obsolete unit of inductance from the electrostatic CGS unit system. It is

In an inductance of a 1 to 1 Stath Statampere per second increasing current produces a voltage of 1 Statvolt.

Before the introduction of the SI one has the current SI Henry called Henry absolute, that of the former definition of the ( international ) Ohm derived Henry, however, as an international Henry. Since the national standard authorities have identified different conversion factors based on the measurement provisions of definitions, there have been different national numbers for the international Henry. The International Committee of Weights and Measures in 1946, the average international ohm determined with 1.00049 Ω, which also applies:

Significant also was the U.S. international Henry: