Maxwell's first equation is known as Gauss's Law, which describes the relationship between electric charge and electric field. In its integral form, it states that the electric flux through a closed surface is proportional to the charge enclosed within that surface:
\[
\Phi_E = \oint \mathbf{E} \cdot d\mathbf{A} = \frac{Q_{\text{enc}}}{\epsilon_0}
\]
Here, \(\Phi_E\) is the electric flux, \(\mathbf{E}\) is the electric field, \(d\mathbf{A}\) is a differential area vector on the closed surface, \(Q_{\text{enc}}\) is the total charge enclosed by the surface, and \(\epsilon_0\) is the permittivity of free space.
In differential form, Gauss's Law can be expressed as:
\[
\nabla \cdot \mathbf{E} = \frac{\rho}{\epsilon_0}
\]
where \(\rho\) is the charge density. This equation highlights how electric fields are generated by electric charges.