The magnetic field  due to a small current element  at a distance  and element carrying current is,

The magnetic field (B) due to a small current element (I) at a distance (r) can be calculated using Biot-Savart Law. Here are the steps:

1. Identify the current element: The current element is a small section of the wire, denoted as dL, through which the current I is flowing.

2. Apply Biot-Savart Law: According to Biot-Savart Law, the magnetic field dB due to this current element at a point located at a distance r is given by:

   dB = μ0/4π * (I * dl * sinθ) / r²

   where, μ0 = permeability of free space, I = current through the element, dl = length of the small element, θ = angle between dl and the line joining the element to the point where we are calculating the magnetic field, r = distance of the point from the element.

3. Integrate the magnetic field: If the wire is not a straight line, or if you want to find the total magnetic field due to the entire wire, you would need to integrate this expression over the length of the wire.

Please note that the direction of the magnetic field is given by the right-hand rule. If you point the thumb of your right hand in the direction of the current, your fingers will curl in the direction of the magnetic field.