# Formula 4th Maxwell Equation in Integral Form Magnetic field Electric current Electric field

## Magnetic field

`$$ \class{violet}{\boldsymbol{B}} $$`Unit

`$$ \mathrm{T} $$`

The magnetic flux density indicates how strong the magnetic field is at a certain location \((x,y,z)\) and in which direction it points.

## Closed line

`$$ L $$`Unit

`$$ \mathrm{m} $$`

Line (e.g. a current-carrying conductor) over which you integrate. It is the edge of the surface \( A \) (for example the edge of a circle). The line must be closed, i.e. its beginning and its end must be connected.

## Surface

`$$ A $$`Unit

`$$ \mathrm{m}^2 $$`

This surface is enclosed by the closed loop \(L\). This can be, for example, the area of a circle.

## Electric current

`$$ \class{red}{I} $$`Unit

`$$ \mathrm{A} $$`

Electric current running along the line \(L\).

## Electric field

`$$ \class{blue}{\boldsymbol{E}} $$`Unit

`$$ \frac{\mathrm V}{\mathrm m} $$`

Electric field tells what would be the electric force on a sample charge at a given location \((x,y,z)\) if that sample charge is placed at that location.

Here the E-field is differentiated with respect to time: \( \frac{\partial \boldsymbol{E}}{\partial t} \).

## Vacuum permeability

`$$ \mu_0 $$`Unit

`$$ \frac{\mathrm{Vs}}{\mathrm{Am}} = \frac{ \mathrm{kg} \, \mathrm{m} }{ \mathrm{A}^2 \, \mathrm{s}^2 } $$`

Magnetic field constant is a natural constant and occurs in the description of electromagnetic phenomena. It is: \( \mu_0 ~=~ 4\pi \cdot 10^{-7} \, \frac{\text N}{\text{A}^2} \).