What is the flux density formula?

Hint: In the question, we are asked to give the formula for flux density. One could first define what magnetic flux is and then move on to defining flux density. After that, recall the formula for magnetic flux density and give the answer. Also give the unit in which this quantity is measured.

Complete answer:
In the question, we are asked to give the formula for flux density. Before going into the discussion regarding magnetic flux density let us understand magnetic flux. We could define magnetic flux as the number of magnetic field lines that are known to pass through a closed surface. The formula for magnetic flux is given by the dot product of magnetic field and area.
Now, we could define magnetic flux density at an arbitrary point as the number of magnetic field lines of force that are passing through a unit cross-sectional area. That is, magnetic flux density could be either given by,
$B=\dfrac{\phi }{A}$
Where, $\phi $is the magnetic flux and A is the area of cross section.
Or as,
$B=\mu H$
Where, H is the magnetic field strength and $\mu $is the magnetic permeability.
Tesla is known to be the SI unit of this physical quantity and is defined as 1 weber flux passing through the unit area of cross-section.

Note: In the above solution, we have discussed the magnetic flux density. We also do have electric flux density and this quantity is given by the following formula.
$D=\varepsilon E$
Here, D is the electric flux density, E is the electric field intensity and $\varepsilon $as we know is the permittivity of the corresponding medium.