Biot-Savart law

A moving point charge produces a magnetic field in addition to its intrinsic electric field. Well, unlike the electric field that radiates outward symmetrically from a point charge, the magnetic field forms circular loops around the moving charge. The Biot-Savart law describes the magnetic field generated by a constant electric current in a similar manner to Coulomb's law describing electric field generated by point charges.

Historically, the Biot-Savart law was deduced by experiment:

• The magnetic field at a point is inversely proportional to its perpendicular distance from the conductor.
  
• The magnetic field is both perpendicular to the conductor and the line formed from the wire to the measuring point
  

It was recorded that the experiment was done by suspending a magnetic needle some horizontal distance apart from a long vertical wire with running current, then showing that the needle moved. Although the Biot-Savart law can only be derived using Maxwell's equations and not the other way around, it discovery precedes both Maxwell's equations and Lorentz force law, i.e. Maxwell's equations were derived in such a way that it encompasses the findings of the Biot-Savart law.