Editing Electromagnetic field (section)

=== Electrostatics and magnetostatics ===
{{main|Electrostatics|Magnetostatics}}
[[File:VFPt image charge plane horizontal.svg|thumb|250px|Electric field of a positive point [[electric charge]] suspended over an infinite sheet of conducting material. The field is depicted by [[field line|electric field lines]], lines which follow the direction of the electric field in space.]]
The Maxwell equations simplify when the charge density at each point in space does not change over time and all electric currents likewise remain constant. All of the time derivatives vanish from the equations, leaving two expressions that involve the electric field,
<math display=block>\nabla \cdot \mathbf{E} = \frac{\rho}{\epsilon_0}</math>
and
<math display=block>\nabla\times\mathbf{E} = 0,</math>
along with two formulae that involve the magnetic field:
<math display=block>\nabla \cdot \mathbf{B} = 0</math>
and
<math display=block>\nabla \times \mathbf{B} = \mu_0 \mathbf{J}.</math>
These expressions are the basic equations of [[electrostatics]], which focuses on situations where electrical charges do not move, and [[magnetostatics]], the corresponding area of magnetic phenomena.{{sfnp|ps=|Feynman|Leighton|Sands|1970|loc=[https://www.feynmanlectures.caltech.edu/II_04.html §4.1]}}