Electromagnetism. James C. Maxwell, 1831-1879. Maxwell's equations are the four basic equations for electromagnetism and electrodynamics. They describe how electric and magnetic fields are generated and altered by each other and by charges and currents.
The first equation (Gauss's law) states that electric charges cause electric fields.
The second equation (Gauss's law for magnetism) declares that magnetic field lines neither begin or end but form loops, i.e. there are no 'magnetic charges'.
The third equation (Faraday's law of induction) states that a time varying magnetic field induces an electric field.
The fourth equation (Ampère's circuital law) describes that a time varying electric field induces a magnetic field.