Magnetic Field due to a current in a Long Straight Wire

For a long straight wire carrying a current i, the Biot-Savart law gives for the magnitude of the magnetic field at a perpendicular distances R from the wire,

The field magnitude B depends on the current and the perpendicular distance R of the point from the wire.

Do you still remember to determine the direction of magnetic field lines by using the right hand rules? LETS TRY!  ^0^

*Grasp the element in your extended thumb pointing in the direction of the current.Your fingers will then naturally curl around in the direction of the magnetic field lines due to that current.