Law
Gauss's law for magnetism
(E12.2.1) E12.2 · The Four Field Equations Together →Statement
The net magnetic flux through any closed surface is always exactly zero.
Symbols and units
| magnetic field | T | |
| outward area element | m² |
When it applies
Always true, for any closed surface, in any magnetic field configuration.
Derivation
An empirical statement: every magnetic field line that enters a closed surface also exits it somewhere else — unlike electric field lines, magnetic field lines never begin or end anywhere.
Watch out for
The zero on the right side holds for EVERY closed surface, always — because an isolated magnetic charge, a monopole, has never been observed.
Connects to