## Current density |

Current density | |
---|---|

Common symbols | J → |

In | A m^{−2} |

I L^{−2} |

In **current density** is the **current density vector** is defined as a ^{[1]}

- definition
- importance
- calculation of current densities in matter
- continuity equation
- in practice
- see also
- references

Assume that *A* (SI unit: ^{2}) is a small surface centred at a given point *M* and orthogonal to the motion of the charges at *M*. If *I*_{A} (SI unit: *A*, then **electric current density** *J* at *M* is given by the ^{[2]}

with surface *A* remaining centred at *M* and orthogonal to the motion of the charges during the limit process.

The **current density vector** **J** is the vector whose magnitude is the electric current density, and whose direction is the same as the motion of the charges at *M*.

At a given time *t*, if **v** is the speed of the charges at *M*, and *dA* is an infinitesimal surface centred at *M* and orthogonal to **v**, then during an amount of time *dt*, only the charge contained in the volume formed by *dA* and **l** = **v** *dt* will flow through *dA*. This charge is equal to *ρ* ||*v*|| d*t* d*A*, where *ρ* is the charge density at *M*, and the electric current at *M* is *I* = *ρ* ||*v*|| *dA*. It follows that the current density vector can be expressed as:

The **J** over a *S*, followed by an integral over the time duration *t*_{1} to *t*_{2}, gives the total amount of charge flowing through the surface in that time (*t*_{2} − *t*_{1}):

More concisely, this is the integral of the **J** across *S* between *t*_{1} and *t*_{2}.

The

The *A*, and a

If the current density **J** passes through the area at an angle *θ* to the area normal , then

where **⋅** is the *J* cos *θ*, while the component of current density passing tangential to the area is *J* sin *θ*, but there is *no* current density actually passing *through* the area in the tangential direction. The *only* component of current density passing normal to the area is the cosine component.

Other Languages

العربية: كثافة التيار

беларуская: Шчыльнасць току

беларуская (тарашкевіца): Шчыльнасьць току

български: Плътност на тока

català: Densitat de corrent

čeština: Hustota elektrického proudu

Deutsch: Elektrische Stromdichte

eesti: Voolutihedus

español: Densidad de corriente

Esperanto: Kurenta denseco

فارسی: چگالی جریان الکتریکی

français: Densité de courant

한국어: 전류 밀도

հայերեն: Հոսանքի խտություն

हिन्दी: धारा घनत्व

hrvatski: Gustoća električne struje

italiano: Densità di corrente elettrica

עברית: צפיפות זרם

ქართული: დენის სიმკვრივე

lietuvių: Srovės tankis

magyar: Áramsűrűség

मराठी: धारा घनता

Nederlands: Elektrische stroomdichtheid

日本語: 電流密度

norsk nynorsk: Straumtettleik

polski: Gęstość prądu elektrycznego

português: Densidade de corrente elétrica

română: Densitate de curent

русский: Плотность тока

slovenčina: Plošná hustota elektrického prúdu

slovenščina: Gostota električnega toka

српски / srpski: Gustina struje

suomi: Sähkövirran tiheys

svenska: Elektrisk strömtäthet

தமிழ்: மின்னோட்டச் செறிவு

Türkçe: Akım yoğunluğu

українська: Густина струму

中文: 电流密度