What is the magnetic flux density at distance r due to a long conductor carrying current of I?

CONCEPT: 

The magnetic field at point P due to a straight conductor is given by:

B = \(μ_0 I \over{2\pi d}\)

where B is the magnetic field at point P, μ0 permeability of the medium I is the current in the in the wire and d is the distance from the wire to that point.

EXPLANATION:

At distance r from an infinitely long straight current carrying conductor, magnetic field is:

B = \(μ_0 I \over{2\pi r}\)

where B is the magnetic field, μ0 permeability of the medium I is the current in the wire, and r is the distance from the wire to that point.

So B α 1/r

Important Points

 Magnetic flux density of coil is given by \(B = \;\frac{{{\mu _o}NI}}{{2R}}\)  T

Magnetic flux density of solenoid is given by \(B = \;\frac{{{\mu _0}\;NI}}{l}\)  T

Magnetic flux density of long straight wire \(B = \;\frac{{{\mu _0}I}}{{2\pi r}}\) T