# 15.4: Maxwell's Second Equation

- Page ID
- 6214

Unlike the electrostatic field, magnetic fields have no sources or sinks, and the magnetic lines of force are closed curves. Consequently the surface integral of the magnetic field over a closed surface is zero, and therefore

\[ \text{div} \, \textbf{B} = 0 \tag{15.4.1} \label{15.4.1}\]

or, in the nabla notation

\[ \boldsymbol{\nabla} \cdot \textbf{B} = 0 \tag{15.4.2} \label{15.4.2}\]

This is the second of Maxwell's equations.