An inductor.
The henry (symbol: H) is the SI unit of inductance. It is named after Joseph Henry (1797-1878), the American scientist who discovered electromagnetic induction independently of and at about the same time as Michael Faraday (1791-1867) in England. The magnetic permeability of the vacuum is 4π×10−7 H/m (henry per metre).
Definition
If the rate of change of current in a circuit is one ampere per second and the resulting electromotive force is one volt, then the inductance of the circuit is one henry.
- <math>H = \dfrac{\mbox{m}^2 \cdot \mbox{kg}}{\mbox{s}^{2} \cdot \mbox{A}^2} = \dfrac{\mbox{Wb}}{\mbox{A}} = \dfrac{\mbox{V} \cdot \mbox{s}}{\mbox{A}} = \dfrac{\mbox{m}^2 \cdot \mbox{kg}}{\mbox{C}^2}</math>
SI multiples
| Submultiples | Multiples | |||||
|---|---|---|---|---|---|---|
| Value | Symbol | Name | Value | Symbol | Name | |
| 10–1 H | dH | decihenry | 101 H | daH | decahenry | |
| 10–2 H | cH | centihenry | 102 H | hH | hectohenry | |
| 10–3 H | mH | millihenry | 103 H | kH | kilohenry | |
| 10–6 H | µH | microhenry | 106 H | MH | megahenry | |
| 10–9 H | nH | nanohenry | 109 H | GH | gigahenry | |
| 10–12 H | pH | picohenry | 1012 H | TH | terahenry | |
| 10–15 H | fH | femtohenry | 1015 H | PH | petahenry | |
| 10–18 H | aH | attohenry | 1018 H | EH | exahenry | |
| 10–21 H | zH | zeptohenry | 1021 H | ZH | zettahenry | |
| 10–24 H | yH | yoctohenry | 1024 H | YH | yottahenry | |
| This SI unit is named after Joseph Henry. As with all SI units whose names are derived from the proper name of a person, the first letter of its symbol is uppercase (H). But when an SI unit is spelled out, it should always be written in lowercase (henry), unless it begins a sentence or is the name "degree Celsius".
— Based on The International System of Units, section 5.2.
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