Oersted experiment showed that a current-carrying conductor produces a magnetic field around it.

A current element denoted by * dl*, which has the same direction as that of current

*From a series of experiments on current-carrying conductors of simple shapes, two French physicists Jean Baptiste Biot and Felix Savart in 1820, deduced an expression for the magnetic field of a current element which is known as Biot-Savart Law.*

**I.****Statement:-**

Consider a current element * dl *of a conductor

*carrying*

**xy***. Let*

**I***be the point where the magnetic field due to the current element*

**P***is to be calculated.*

**dl**Biot-Savart law |

According to Biot-Savart law, the magnitude of the field * dB* is

**Note:-**Proportionality constant K depends on the medium between the observation point P and the current element and the system of the unit chosen, for free space SI units is

Here

**μo**is a constant called the permeability of free space. So the Biot-Savart law expressed as### Special Cases

- If θ=0,sinθ=0, so that dB=0 i.e., the magnetic field is zero at the point on the axis of the current element.
- If θ=90,sinθ=1, so that dB is maximum i.e. the magnetic field due to a current element is maximum in a plane passing through the element and perpendicular to its axis.